review article microwave heating as an alternative...

Hindawi Publishing CorporationInternational Journal of Food ScienceVolume 2013 Article ID 926468 13 pageshttpdxdoiorg1011552013926468

Review ArticleMicrowave Heating as an Alternative Quarantine Method forDisinfestation of Stored Food Grains

Ipsita Das1 Girish Kumar1 and Narendra G Shah2

1 Department of Electrical Engineering Indian Institute of Technology Bombay Powai Mumbai 400076 India2 Centre for Technology Alternatives for Rural Areas Indian Institute of Technology Bombay Powai Mumbai 400076 India

Correspondence should be addressed to Ipsita Das ipsitdasgmailcom

Received 17 December 2012 Accepted 28 February 2013

Academic Editor Mitsuru Yoshida

Copyright copy 2013 Ipsita Das et alThis is an open access article distributed under theCreativeCommonsAttribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Insects and pests constitute a major threat to food supplies all over the world Some estimates put the loss of food grains becauseof infestation to about 40 of the world production Contemporary disinfestation methods are chemical fumigation ionizingradiation controlled atmosphere conventional hot air treatment and dielectric heating that is radio frequency and microwaveenergy and so forthThough chemical fumigation is being used extensively in stored food grains regulatory issues insect resistanceand environmental concerns demand technically effective and environmentally sound quarantine methods Recent studies haveindicated that microwave treatment is a potential means of replacing other techniques because of selective heating pollutionfree environment equivalent or better quality retention energy minimization and so forth The current paper reviews the recentadvances in Microwave (MW) disinfestation of stored food products and its principle and experimental results from previousstudies in order to establish the usefulness of this technology

1 Importance of Disinfestation

Agricultural commodities produced on the fields have toundergo a series of operations such as harvesting threshingwinnowing bagging transportation storage and processingbefore they reach the consumer and there are appreciablelosses in crop output at all these stages Various estimateshave been made to assess the postharvest food grain lossesThe losses are caused either by environmental factors suchas temperature moisture and type of storage structure or bybiological agents namely insects rodents birds and fungiThemajor losses during production storage andmarketing offood grain are being attributed to infestation by insect pestsmicrobiological contamination and physiological changesInsect infestations can occur just prior to harvest or duringstorage or in-transit in a variety of carriers The occurrenceand numbers of stored grain insect pests are directly relatedto geographical and climatic conditions [1] Almost all specieshave remarkably high rates of multiplication and within oneseason may destroy 10ndash15 of the grain and contaminate therest with undesirable odors and flavors Insect pests also play

a pivotal role in transportation of storage fungi [2]Thereforepreventing economic losses caused by stored-product insectsis important from the field to the consumerrsquos table [3] Thelosses during storage are classified as quantity losses and qual-ity losses Quantity losses occur when the grain is consumedby insects rodents mites birds andmicroorganisms Qualitylosses are reflected as reduced economic value of the cropThestored-grain insects affect not only the quantity of grain butalso the quality of grain Infestation causes decreased nutri-tional value reduced seed germination and lower economicvalue and also causes changes in chemical compositions suchas increase in moisture free fatty acid levels nonproteinnitrogen content and decrease in pH and protein contents infood grain [4] They reduce the product quality directly bydamage through feeding and indirectly by producing web-bing and frass [5] Also the grain quality has been found todecrease with time with increasing levels of infestation [6] Itis estimated thatmore than 20000 species of field and storagepests destroy approximately one-third of the worldrsquos foodproduction valued annually at more than 100 billion dollar[7] The quantitative and qualitative damage to stored grains

2 International Journal of Food Science

and grain product from the insect pests may amount to 20ndash30 in the tropical zone and 5ndash10 in the temperate zone [8]Food grain production in India has reached 250 million tonsin the year 2010-2011 in which nearly 20ndash25 food grainsare damaged by stored grain insect pests [7]With populationgrowth and the amount of cultivatable land shrinking grainlosses will continue to be a problem in the developing coun-tries Control of stored-product pests is one of themajor tasksbecause the damage inflicted to foodstuff is irreversible Alsowith progressive increase in the quantity of food grains andnecessity for longer storage periods these losses will escalateunless disinfestation measures are improved Internationalorganizations such as FDA [9] and FGIS [10] have set toler-ances and grade standards regulating the number of insectsand insect fragments above specified tolerances to makethe product illegal for human consumption In developedcountries even the mere presence of a few insects in a bulkat densities of considerably less than one insect per kg graincan cause a serious loss in itsmarket value In some developedcountries grain can be downgraded or rejected completely ifeven a single live insect is found [11]The efficient control andremoval of stored grain pests from food commodities havelong been the goal of entomologists throughout the worldVarious methods of insect control have been practiced tosave the grain In recent years technology has made markedprogress in the study of disinfestation of stored-grain insectsand of finding improved ways to control them especiallyto detect latent forms of infestation The implementation ofan insect-disinfestation method requires detailed analysis ofall the elements of an infestation problem the insects theirage species and distribution and their survival and develop-mental rates under different environmental conditions [12]Conventional chemicals grain protectants and fumigants areextensively used around the world to control insect pests instored commodities because of low cost fast processing andeasy application Greater regulation and restriction of methylbromide use will likely increase the cost of the fumigant aswell as reduce its availability [13] With the concerns abouthealth hazards of chemical pesticides and their resultingenvironmental pollution there is interest in developing alter-native nonchemical process protocol to control insect pestswhile retaining acceptable product quality These includeconventional hot air or water heating controlled atmosphereand dielectric heating (radio frequency (RF) and microwave(MW)) Currently the use of chemical fumigation remainswidespread and the efficient use of RF and MW methodsfor disinfestation is still in research stage The currentpaper reviews the various disinfestation methods of storedfood grains with special emphasis on recent advances inmicrowave disinfestation of stored food grains The principleof microwave disinfestation experimental results of qualitycharacteristics of microwave-treated grains and the chal-lenges of microwave disinfestation have also been described

2 Various Methods of Insect Control

The control of stored-product insects is very important ifthe quality of foodstuff is to be maintained The goal of

the control measure is to render the habitat unsuitable forthe growth and reproduction of stored-product insects Thefive major potential quarantine treatment methods used fordisinfestation of several insect pests for both the domesticand international markets are chemical fumigation ionizingradiation controlled atmosphere conventional hot airwaterheating and dielectric heating using radio frequency (RF)and microwave (MW) energy which have been described inthis paper

21 Chemical Method Since the 1950s chemical insecticideshave beenused extensively in grain storage facilities to controlstored-product insect pests due to low cost fast speed in pro-cessing and ease of use Most postharvest pest managementprograms therefore rely heavily on fumigants Currentlyover 25 million tons of chemicals worth over 30 billion USdollars are applied to crops in the world [14] The chemicalsused to control insects in the bulk stored-grains are composedof two classes namely contact insecticides and fumigantsContact insecticides such asmalathion chlorpyrifos-methylor deltamethrin are sprayed directly on grain or structureswhich provide protection from infestation for several months[15] Fumigants are gaseous insecticides applied to controlinsects in grains that are inaccessible by contact insecticideSome of the commonly used fumigants are methyl bromide(MeBr) and phosphine which rapidly kill all life stages ofstored-product insects in food product [16] Methyl bromideis now under the threat of withdrawal because it apparentlydepletes the Earthrsquos ozone layer [17] It has already beenestablished that the use of MeBr has led to serious envi-ronmental damage and hazards to peoplersquos health For thesereasons the Montreal Protocol constituted by the UnitedNations Environment Programme agreed on a phasing outof methyl bromide in the developed countries by 2005 andin the developing countries by 2015 [18] Phosphine has beenused as a replacement of methyl bromide for a long time[19] Conventional use of phosphine has failed frequently tocontrol insects [20] Another limiting factor is that insectsdevelop resistance to some particular chemical fumigantsSome of the contact insecticides have become ineffectivebecause of wide-spread resistance in insect populations Aworldwide survey of stored-product insects revealed that 87of 505 strains of the red flour beetle Tribolium castaneumcollected from 78 countries were resistant to malathion [15]Resistance to malathion is widespread in Canada USAand Australia [21] while resistance to phosphine is greatin Australia and India which may cause control failures[22] The other major problem associated with the chemicalmethods is that even if they are applied with care and inlimited quantity there is a possibility that these chemicalsmay remain in the food grains and have adverse effectson humans Fumigation often only kills live larvae or adultinsects but does not sterilize the eggs which are still alive inthe grain kernels [23] The consumption of organic productsis also increasing each year There is therefore interest indeveloping an alternative nonchemical process method tocontrol insect pests in food grains so as to minimize theenvironmental hazards associated with chemical insecticideswhile retaining acceptable product quality

International Journal of Food Science 3

22 Ionizing Radiation It is a process where infested foodproducts are being exposed to ionizing radiation so asto sterilize kill or prevent emergence of insect pests bydamaging their DNA Three types of ionizing radiationused on foods are gamma rays from radioactive cobalt-60 and cesium-137 high energy electrons and X-rays [24]Irradiation with high energy electrons is usually safer andeasier to work with because it can be turned on and offwhile an isotope is always radiating and humans must beshielded from it [25] The ability of gamma rays to deeplypenetrate pallet loads of food makes it one of the mostcommonly used in postharvest pest control Sterilization ofmany species of insects can be accomplished at lower dosesRusty grain beetles are sterilized at only 06 kGy but saw-toothed grain beetles and red flour beetles require a 20 kGydose [26] The grain mite however requires a much higherdose of 45 kGy Though irradiation doses of 3ndash5 kGy werereported to be effective in controlling insects they causedamage to product quality [26] According to Hasan andKhan [27] high dosage of ionizing radiation has a risk ofvitamin loss from the food product The major drawbackis substantial initial investment to establish the facility Inorder to be economically feasible the facility must remainin continuous operation However the seasonal nature offood produce prevents efficient use of facilities Besides thismethod has not received wide recognition because of highpower consumption large weight and overall sizes of theinstallation Consumers also have concerns over the disposalof radioactive wastes the safety of the irradiation technologyand its effect on food [28] Irradiation treatments often leadto live insects found by inspectors or consumers in the treatedproduct because the applied doses do not immediately killtreated insects [29 30] Grains will continue to appear tobe infested and a grain buyer cannot be certain that theinsects are sterilized Following irradiation with gamma raysat 05 kGy complete insect mortality occurs in 14 days forrusty grain beetles 28 days for red flour beetles 70 days forsaw-toothed grain beetles and 200 days for grain mites Todate irradiation is not accepted by the organic industry Alsoapprovals for irradiation of some selected food products (egalmond) have not been accepted by many countries such asEU Japan and Taiwan [31]

23 Controlled Atmosphere Storage Controlled atmospherea disinfestation technology wherein the normal compositionof atmospheric air that is 21 O

2 003 CO

2 and 78

nitrogen is altered appropriately for disinfestation process[26] An atmosphere containing more than 35 CO

2known

as carbon dioxide atmosphere and the atmosphere containingless than 1 oxygen that is low-oxygen atmosphere arelethal to insects Controlled atmospheres are mainly basedon the establishment of a low-oxygen environment whichkills pests The oxygen levels vary between 0 and 2 Itcan be applied in airtight environments ranging from 1M3to 1000M3 depending upon food commodity Insects in allstages are eliminated because of the lack of oxygen whichcauses the insect to dry out and suffocate This controlledatmosphere (CA) storage has been shown to be promising

in creating lethal conditions for insects and fungi in storedfood commodities Annis and Morton [36] studied the effectof 15 to 100 CO

2on developmental stages of insects in

wheat at 25∘C and 60 RH They found that pupae werethe most tolerant stages for all CO

2concentrations and eggs

were the only stages with 100 mortality at 20 CO2for

less than 30 days Gunasekaran and Rajendran [37] alsofound that the pupae stages were the most tolerant stageswhen exposed to different concentrations of CO

2 Controlled

atmospheres are always being seen as average alternativesuch as longer treatment time usability and availability andbeing not suitable for dealing with high level of infesta-tion

24 Conventional Heat Treatment Compared to the useof chemical methods heat disinfestation has the potentialfor high market acceptance because of being residue-freeMost research focused on using hot air (80∘C to 100∘C)for disinfestation of food grains and showed satisfactoryresults Thermal treatment methods using hot airhot wateralone or in combination with cold or controlled-atmosphere(CA) storage conditions have been investigated extensivelyfor disinfestation of number of stored commodities [28 38ndash55] The hot air used to increase the temperature of thefood product lies above the thermal limits of survival of thepestinsect Heat disinfestation treatments are relatively easyto apply leave no chemical residues and may offer somefungicidal activity There are a number of factors that affectthe mortality of insects when exposed to hot air such asduration of exposure temperature species and stage Idealtemperatures for growth reproduction and movement formost stored product insects are between 25∘C and 35∘C [56]Many insect larvae can bore into the center of fruits nutsseeds or kernels so the center of the commodity must beheated to lethal temperatures Reported heating times forfruit center to reach the desired maximum temperaturesrange from 23min for cherries to 6 h for apples [48 49]Conventional heating consists of heat transfer from theheating medium to the fruit surface and then conductiveheat transfer from the surface to the center A commondifficulty with hot air or water heating methods is theslow rate of heat transfer resulting in long treatment time[57] Prolonged heating is proved to be detrimental to thequality of final products such as peel browning pitting poorcolor development and abnormal softening and may not bepractical in industrial applications ([58] cited by [59])Therewere reports of damage to grapefruits and mangos whenexposed to forced air at 46∘C for 375 h and 45∘C for 18 hrespectively ([60 61] cited by [48]) Flavor and appearance ofair-heated grapefruits at 46∘C for 3 h were inferior to thoseof unexposed fruits [62] Surface browning in avocados wasobserved when heated with hot air at 43∘C for 35 h [63] andin apples when exposed to hot water treatment at 46∘C for45min [64] A long exposure time requirement also causesalterations to flavor compounds [65] The low heating ratesalsomay increase the thermotolerance of the few insects [66ndash68] which was caused by the induction of heat shock proteinsin insects during sublethal thermal conditions [69] It is alsoimportant to determine the time-temperature combinations


that result in 100 mortality for each insect over relativelylarge range of temperature Sometimes temperature and timecombinations required to kill the target insects may exceedthose that reduce the crop nutrients germination or shelflife [70]The disadvantages associated with conventional heattreatment method stimulated further studies on the possibleuse of dielectric heating for controlling stored-grain insects

25 Dielectric Heating Dielectric heating which covers bothradio frequency (RF) andmicrowave (MW) has been investi-gated for insect control in foods [71] Radio frequency (RF)heating is akin to microwave heating but utilizes anotherpart of the electromagnetic spectrumThe frequency used forMW is 2450MHz or 915MHz while for RF the frequencyis of 13 27 or 40MHz [48] The effects of RF and MWenergy are generally believed to be mainly thermal in nature[72] Most agricultural products that considered dielectricmaterial can store electric energy and convert electric energyinto heat [49] As the wavelength of RF heating frequenciesis 22 to 360 times as more than that of the microwavefrequencies this allows RF energy to penetrate dielectricmaterials more deeply than microwaves Many studies haveexplored the use of RF heating for control of insects inagricultural commodities [31 47 49 73ndash82] Researchershave reported the acceptable product quality after treatingnuts and rice with RF energy to control insect infestation [4876ndash78 83ndash85] Recently Wang et al [81] studied postharvestdisinfestation treatments for chickpeas and lentils using RFenergy and also reported acceptable product quality But theradio frequency heating is particularly useful when appliedto institutional-sized packaged food products because of itsdeep penetration [86 87]

Thermal treatment methods involving microwave radia-tion have extensively been investigated by several researchersas an alternative method of killing insects Microwavequarantine method seems to have a great potential as analternative method of killing insects in stored grain becauseof several advantages such as the control of all developmentalstages of storage pests having no chemical residues on thefood product having minimal impact on the environmentand providing rapid heating [28 88ndash90] Insects are unlikelyto develop resistance to this treatment [91] This electro-magnetic energy (MW and RF) interacts directly with theproductrsquos interior to quickly raise the center temperature[47ndash49] Microwave radiation not only kills insects by thedielectric heat induced within them but also affects thereproduction of survivors [92] Microwave radiation withgood penetrability can kill pests existing inside or outsidegrain kernels [93] This paper brings the research initiativesespecially onmicrowave (MW) heating for their potential usefor disinfestation of stored food grains

251 Microwave Heating Microwaves are electromagneticwaves with frequencies ranging from about 300MHz to300GHz and corresponding wavelengths from 1 to 0001m[94] In electromagnetic spectrum microwaves lie betweenradio frequencies and infrared radiation Microwave heatingis based on the transformation of alternating electromagnetic

field energy into thermal energy by affecting polar moleculesof a material Many molecules in food (such as water andfat) are electric dipoles meaning that they have a positivecharge at one end and a negative charge at the other andtherefore they rotate as they try to align themselves with thealternating electric field induced by the microwave beamThe rapid movement of the bipolar molecules creates frictionand results in heat dissipation in the material exposed to themicrowave radiation Microwave heating is most efficient onliquidwater andmuch less on fats and sugars (which have lessmolecular dipole moment) [95] The most important char-acteristic of microwave heating is volumetric heating whichis different from conventional heating The electromagneticenergy directly interacts with commodities to raise the inte-rior temperature and significantly reduce treatment times ascompared to conventional hot-water immersion and heatedair methods Conventional heating occurs by convection orconduction where heat must diffuse from the surface of thematerial Volumetric heatingmeans thatmaterials can absorbmicrowave energy directly and internally and convert it intoheatThe power generated in a material is proportional to thefrequency of the source the dielectric loss of the materialand the square of the field strength within it The conversionof microwave energy to heat is expressed by the followingequation [96]

119901 = 21205871198642119891120576101584010158401205760119881 (1)

where 119901 power W 119864 the electric field strength Vm 119891 thefrequency Hz 120576

0 the permittivity of free space Fm 12057610158401015840 the

dielectric loss factor and 119881 volume of the material m3Dielectric properties of food depend on composition

temperature bulk density and microwave frequency Sincethe influence of a dielectric depends on the amount of massinteracting with the electromagnetic fields the mass per unitvolume or density will also have an effect on the dielec-tric properties This is especially notable with particulatedielectrics such as food grains For granular and particulatematerials both the dielectric constant and loss factor tend toincrease linearly with increasing bulk density of the materialsespecially in lower moisture materials such as cereal grains[97]

252 Microwave Disinfestation The use of microwaves fordisinfestation is based on the dielectric heating effect pro-duced in grain which is a relatively poor conductor ofelectricity An attractive feature of the insect control usingthe microwave energy is that the insects are heated at a fasterrate than the product they infest because of high moisturecontent of insects So it is possible to heat the insects to alethal temperature because of their high moisture contentwhile leaving the drier foodstuff unaffected or slightly warm[12] Raising the temperature of infested materials by anymeans can be used to control insects if the infested productcan tolerate the temperature levels that are necessary to killthe insects There has been a lot of research on microwavedisinfestation of cereals especially wheat [33 98ndash104] and ofsome other foodmaterials such as nuts [28] corn [105] pulses[106 107] and cherries [89] Exposure to microwave energy


Table 1 Dielectric properties of insects at 20ndash25∘C ([32] cited by[33])

Frequency (GHz)Adult insect species 02 24 94 20

120576101584012057610158401015840120576101584012057610158401015840120576101584012057610158401015840120576101584012057610158401015840

S oryzae 28 12 17 3 17 3 mdash mdashL decemlineata 53 81 38 12 30 16 19 17S oryzae 42 28 32 9 25 12 18 13S oryzae 55 48 42 13 31 16 23 16T castaneum 61 56 47 15 34 19 25 19O surinamensis 70 68 53 17 40 21 28 22R dominica 63 55 43 15 34 19 25 181205761015840 dielectric constant 12057610158401015840 dielectric loss

could cause physical injuries and reduced reproduction ratesin surviving insects [75]

Feasibility of microwave disinfestation of insect pests hasbeen explored by Andreuccetti et al [74] for woodwormsand by Halverson et al [108] for wheat maize and flourweevils (cited by [89])Nelson [75] reviewed the susceptibilityof various stored grain insect species to radio frequencyand microwave treatments The use of microwave energyto control insects was initiated by Webber et al [109] andthe literature prior to 1980 has been reviewed by Tiltonand Vardell [98] Researchers have reported that microwavetreatment is an attractive quarantine treatment The majoradvantage of microwave heating is that it interacts directlywith food grains and significantly reduce the amount oftime required for food grain to reach the lethal temperaturefor insects as compared with conventional heating methodsBased on microwave heating theory and dissipated powercalculations in (1) the absorption of microwave energy isproportional to the dielectric constant and dielectric lossfactor of the materials The dielectric properties of thematerials depend on the frequency of the applied electric fieldand the temperature of the material [110] If the material ishygroscopic dielectric properties also depend on the amountof water in the material [111]

The first reported measurements of insect dielectricproperties were for rice weevil and flour beetle at 40MHzfrequency The dielectric constants were 66 and 78 for riceweevil and flour beetle respectively and loss factor was 22for both species [112ndash114] Nelson [110] presented data thatconfirms the dielectric loss factor of the insects was found tobe much higher than that of stored-grain insects The insectpermittivity data at 25∘C for 247GHz frequency reported byNelson et al [32] are shown in Table 1 Alfaifi et al [115] havereported that the loss factor of insect pests such as Indianmeal moth (Plodia interpunctella) and navel orangeworm(Amyelois transitella) is 26 to 36 times greater than that ofdried fruits Wang et al [28 48 49] have indicated preferen-tial heating of insects when walnut kernels and codling mothwere subjected to radio frequency (27MHz) and microwavefrequency (2450MHz) heating Similar finding was observedby Ikediala et al [116] and Raskovan et al [117] for insectinfested grain when subjected to radio frequency heating

Table 2 Dielectric properties of selected food products at 20∘C

Food product Dielectric constant Dielectric loss915MHz 2450MHz 915MHz 2450MHz

Apple 57 54 8 10Almond 21 mdash 26 mdashAvocado 47 45 16 12Banana 64 60 19 18Carrot 59 56 18 15Cucumber 71 69 11 12Dates 12 mdash 57 mdashGrape 69 65 15 17Grapefruit 75 73 14 15Lemon 73 71 15 14Lime 72 70 18 15Mango 64 61 12 14Onion 61 64 12 14Orange 73 69 14 16Papaya 69 67 10 14Peach 70 67 12 14Pear 67 64 11 13Potato 62 57 22 17Radish 68 67 20 15Strawberry 73 71 14 14Walnut 32 mdash 64 mdashSource see [34]

They have reported that the dielectric constant and dielectricloss factor for granary weevil were greater than those of hostgrain in frequency band from 2 to 150MHz The reasonattributed is that the higher the water content the higherthe values of dielectric properties of a material [118] whichconsist of dielectric constant (1205761015840) anddielectric loss factor (12057610158401015840)described by the complex relative permittivity 120576lowast [115 119]

120576lowast= 1205761015840minus 11989512057610158401015840 (2)

where 119895 = (minus1)05 1205761015840 = real component a measure ofthe ability of the material to store electromagnetic energyand 12057610158401015840 = Imaginary component a measure of the ability todissipate electrical energy into heat

Table 2 shows the dielectric permittivity of food whensubjected to microwave heating Hallman and Sharp [120]also summarized research on the application of radio fre-quency and microwave heat (electromagnetic energy) treat-ments to kill different pests on many postharvest food cropsPower level and exposure time of microwave have been iden-tified as two important parameters to provide 100 insectmortality [101] Microwave energies have been investigatedfor a number of food products other than cereal grains suchas pulses nuts cherries and dates Recently the effect of themicrowave-heating method has been studied on disinfesta-tions of the stored green gram seed [107] The power leveland exposure time were optimized based on insect mortalitycolor and antinutrient factor with the value of power andexposure time of 800W and 80 s respectively Singh et al[106] have also studied the disinfestation of pulse beetle (adult


stage) in chickpea pigeon pea and green gram as a functionof exposure time and power level by exposing it continuouslyto microwave radiation (2450MHz) The mortality of insectwas found to increase with increase in microwave exposuretime and power level or both Though seed viability andgermination of all these pulses were found to be affectedthe cooking and milling characteristics were not affected bymicrowave exposure time and power level Campana et al[121] and Bhaskara Reddy et al [122] that though eradicationof the insects increased with the increase in microwaveenergy but the seed viability germination capacity andseedling vigour decreased by exposure to microwave energyVadivambal et al [104] and Vadivambal [33] had studied themortality of different life stages of three common stored-graininsects namely Tribolium castaneum (Herbst) Cryptolestesferrugineus (Stephens) and Sitophilus granarius (L) in wheatbarley and rye respectively using industrialmicrowave dryeroperating at 245GHz Grain samples of 50 g at 14 16and 18 moisture content (wet basis) were exposed to fourdifferent power levels of 200 300 400 and 500W for twoexposure times of 28 and 56 s Complete (100) mortalitywas achieved for adults of all three insect species at 500W foran exposure time of 28 s The average temperature of wheatbarley and rye at 500W and 28 s was around 80∘C 71∘C and82∘C respectively In all the cases eggs were found to bemostsusceptible followed by larvae and the least susceptible werethe pupae and adults Halverson et al [103] had also reportedthat egg and young larva of all the three species were moresusceptible than the pupa when microwave energy at 28GHzfrequency The species tested were S granarius T castaneumand R dominica Germination of seeds was lowered with anincrease in power level or exposure time or both but there wasno significant difference found in the quality characteristics ofmicrowave-treated and control wheat barley and rye exceptfor a decrease in the flour yield There were also reports byseveral researchers that no significant difference in the qualityof grain protein flour protein flour yield and loaf volumeof sample was found when treated with microwave energy atwhich 100 mortality was obtained

Kaasova et al [123] studied the chemical and biochemicalchanges during microwave treatment of wheat and reportedthat an improvement in the baking quality was foundat higher energy doses and higher product temperaturesThe decrease in germination capacityseedling viability wasrelated to the final temperature and the initial moisturecontent of the grains Hamid and Boulanger [124] had foundthat the bread making quality of wheat was affected withincrease in treatment temperature when exposed to powerof 12 kW They reported that 70 and 100 mortality wereobtained when the wheat temperature was 55∘C and 65∘Crespectively while Locatelli and Traversa [125] have reportedthat temperature of grain has to reach 80∘C for achievingcomplete mortality of insects infected using microwave Infact most infesting biological agents do not survive overa certain temperature called lethal temperature generallybetween 55∘C and 60∘C which can be rapidly reachedthrough microwave irradiation [40] There are three tem-perature zones for all insects optimum the zone at whichhighest rate of development can be achieved suboptimum

Table 3 Response of stored-product insects to temperature [35]

Temperature (∘C) Zone Effect50ndash60 Lethal Death in minutes45 Death in hours35 Suboptimum Development stops33ndash35 Development slows25ndash33 Optimum Maximum rate of development13ndash25 Suboptimum Development slows13ndash20 Development stops5

LethalDeath in days

minus10 to minus5 Death in weeks to monthminus25 to minus15 Death in minutes insects freeze

a zone below or above optimum during which insects cancomplete their life cycle and thirdly lethal zone above orbelow suboptimum zones when insects get killed over periodof time (Table 3) But the lethal temperatures to kill insectswere found to vary considerably not only with species butalso with the stage of development temperature and relativehumidity When developing effective treatment protocols itis essential to determine which of the targeted insects is themost heat resistant as well as the most heat resistant lifestage for each species To accomplish this information isrequired on the minimum time-temperature combinationsthat result in 100 mortality for each insect over a relativelylarge range of temperature The thermal death kinetics forfifth-instars of Indian meal moth codling moth and navelorange worm have been separately reported [76 77 126ndash129] The authors of [130] recommended 15min exposures tomicrowaves which increased temperature to 60∘C to kill allinsects in confectionery walnuts without adversely affectingflavor

Halverson et al [103] conducted experiments to deter-mine life stages of the insect that is most susceptible tomicrowave energy at 28GHz frequency The life stages testedwere egg young larva and pupa Their results suggestedthat egg and young larva of all were always more susceptiblethan the pupa Zouba et al [131] had employed a research-scale microwave unit to investigate the mortality of insectin date and the thermal impact on the date quality Theheating characteristics of dates are highly influenced by initialmoisture content Date having various moisture contents getsheated up in a very heterogeneous manner and the energyof the microwaves seems to be preferentially absorbed bysoft dates Similar results were reported during insect controlof walnuts using radio frequency treatments The insectmortality is achieved in less than 90 s during microwavetreatment without altering date quality

253 Challenges in Microwave Disinfestation Althoughmicrowaves have potential for disinfestation applications inthe grain industry they have not been used widely due totheir adverse effects on various quality parametersThemajorproblems associated with microwave heating are the nonuni-form temperature distribution and thereby incomplete killof microbes [132ndash137] Hot spots produced on products


due to the nonuniform heating pattern of microwaves areone of the important factors for the quality degradation ofproducts during microwave treatment A hot spot can bedefined as a local area of very high temperature that resultsfrom the temperature dependence of material propertiesAlthough hot spots are desirable to increase insect mortalitydetrimental effects on the medium are not Manickavasaganet al [138] had determined the germination percentage ofmicrowave-treated wheat samples collected from hot-spotand normal heating zones The wheat samples having fourdifferent moisture levels (12 15 18 and 21 wb) weresubjected to different microwave treatments (100 200 300400 and 500 watt with exposure times of 28 and 56 s)in continuous industrial microwave dryer (2450MHz) Thegermination percentage of the sample in the hot-spot regionwas significantly lower than that of the normal heating regionfor all moisture and power levels Apart from germinationthe other quality parameters were also found to get affectedmore in the hot-spot zone than the remaining bulk grainMoreover the generation of ldquohot spotsrdquo during industrialmicrowave heating has recently become of great concernto scientists involved in microwave research [139 140] Theothermajor drawback inmicrowave disinfestation is the poorpenetrating power of microwaves The microwaversquos intensitydiminishes with increased penetration It has been reportedthat microwave treatment of bulk grain is not feasible whenthe depth is greater than 4 inch ([92] cited by [33]) Dueto the limited penetration of microwave energy into food-stuff mass it seems likely that employment of microwaveradiation alone could not be considered as a promisinginsect control measure under field condition Disinfestationsof stored products using microwaves energy coupled withother modes of treatment can be an alternative measure inkilling insects effectively but little work has been reportedon combined application The mechanisms involved in thelethal action of microwave radiation are already understoodMicrowave radiation has effects on insects such as reductionof reproductive rate losing body weight and malformation[75] However application of microwaves radiation could belimited due to insufficient penetration depth Songping etal [140] reported that microwaves attenuate exponentially inpenetration to foodstuffs

Combined application of microwaves with hot-air treat-mentcold storagegamma radiation could be considered asa potential measure which can help reduce stored-productinsects population The combined impact of microwaveradiation and cold storage on adults was evaluated by severalresearchers Ayvaz and Karaborklu [141] had reported thatthere is a decrease in reproductive ability and number ofliving adults depending on the length of the cold storageperiod In general the reduction of temperature in theenvironment stresses the insect thereby making it moresusceptible to other control measures [48 89] The majoradvantage is that the cold storage can easily be coupled withmicrowave radiation for pest control measure There wassufficient indication that longer microwaves energy exposureand cold storage duration could achieve better kill thanshorter ones of similar power level When the insects suchas Tribolium castaneum H and Sitophilus oryzae L were

exposed to 2450MHz at power level of 100W for exposuretime 10min continuously and intermittently the highestrate of mortality was achieved for intermittent exposuretime of 10min and 72 h of cold storage duration [142]Valizadegan et al [143] have also evaluated the impact ofmicrowave radiation in conjunction with cold storage onadult insects (saw-toothed grain beetle and cigarette beetle)under laboratory conditions The insects were exposed to2450MHZ at five different power levels of 0 100 200 300and 400W for five exposure times of 0 3 6 9 and 12minThe complete control was achieved at 400W power levelsfor exposure time of 12min and 72 h cold storage periodSimilar results that is high mortality rate were also reportedby Nasab et al [5] when Indianmeal moth eggs were exposedto power levels of 100 300 and 500W with 2 4 6 8and 10min exposure duration along and then kept in coldstorage conditions (4 plusmn 1∘C) for 24 and 48 h Combinationsof microwave radiation and cold storage were found to becompatible and synergistic which provide an effective andenvironmentally friendly disinfestation treatment technique

Researchers have also tried the microwave heating alongwith gamma irradiation to control insects in stored cerealsand cereals products El-Naggar andMikhaiel [144] evaluatedthe biochemical analyses on the samples of wheat grainand flour subjected to combined microwave and gammairradiation treatment where high mortality was obtainedTherewere no detectable changes in the quality of protein fatfiber carbohydrates or ash Amjad and Akbar Anjum [145]stated that when onion seeds (Allium cepa L) were exposedto various doses of gamma radiation that is 0 20 40 80and 100 krad there was no significant effect on seed viabilityexcept at the highest dose (100 krad) which resulted inreduced viability But several other researchers reported thatmicrowaves are not suitable for the drying of wheat which isto be used as seeds even using low power levels unless someprovisions are made to ensure uniform heating [124 146ndash148]They have concluded that breadmaking quality of wheatand maize get adversely affected by exposure to microwaveradiationThough microwave heating helped in reducing thepower consumption in wheat milling process the texturalcharacteristics of the final products are made from themicrowave-treated flour were found not to be acceptableTheviscosity of the flour decreased with increased exposure timebecause of the alteration in structure of starch and proteinwhen exposed to microwave energy Campana et al [121]had also stated that the protein content was not affected butthe functionality of gluten altered gradually with increasingtime of exposure The change in the functionality of gluten isbecause of the absence of elasticity and stretchability of thedough [121 147]

Several researchers concluded that germination capacitywas affected by exposure to microwave energy The seedviability and germination of chickpea pigeon pea and greengram were also reported to be affected by microwave expo-sure time and power level [106] Vadivambal et al [149] foundthat microwave energy at 2450MHz with similar heatingmechanism to RF treatments might control storage insects inbarley and rye but resulted in poor germination due to highsample temperatures The decrease in germination capacity


was related to the final temperature and the initial moisturecontent of the grains Nelson and Stetson [150] studied thedielectric heating treatments of rice weevils in wheat at 39and 2450MHz and showed that the lower frequency wasmuch more effective in killing the insects Wang et al [86]had concluded that differential heating of insects in walnutsdoes occur at 27MHz but not at 915MHz based on theexperiments carried out on dried nuts and fruits by exposureto microwave and radio frequencies range

Bhaskara Reddy et al [122] studied the effect ofmicrowave treatment on quality of wheat seeds infected withFusarium graminearum (Schwabe) Their results showed thatthough mortality of insect increased with the microwavepower level but the seed viability and seedling vigordecreased accordingly It has been concluded that microwavedrying of wheat would not be suitable where the final prod-ucts made out of flour required soft textural characteristicsAnother issuewith themicrowave heating is the large numberof factors that affect the microwave heat transfer behaviorsuch as the thickness the geometry and the dielectricproperties of the food The heat capacity and the dielectricproperties (dielectric constant loss factor) change with themoisture content and temperature which complicates themicrowave heating process Cost estimates for microwaveand radio frequency insect control are estimated to be aroundthree to five times more expensive than chemical control

3 Conclusion

Insects cause considerable damage to food grains with weightand nutritional losses reducing yields and market valuesPostharvest phytosanitary treatments are often required tocompletely control insect pests before the products aremoved through marketing channels to areas where the pestsdo not occur Several methods have been suggested tocontrol insect pests in agricultural commodities includingchemical fumigation thermal treatment ionizing radiationcold storage controlled atmospheres dielectric heating andcombination treatments Current technologies involve theuse of toxic chemicals which is neither consumer friendly norenvironmentally friendly and conventional thermal methodsare either undesirable or cause loss of volatile componentsbrowning and texture change To date irradiation is notaccepted by the organic industry Based on the results ofthe microwave disinfestation studies already conducted itis considered as safe and competitive alternative method toother quarantine methods and can avoid problems of foodsafety and environmental pollution The study conductedon different food products infested with major insects saysthat complete mortality that is 100 could be achievedusing microwave energy Although microwaves have poten-tial for disinfesting the food products they have not beenused widely due to their adverse effects on various qualityparameters Nonuniformity of heating is one of the importantfactors that cause quality deterioration of food productThough several practicalmeans can be used tominimize non-uniform heating such as adding forced hot air to the productsurface or sample movementrotation or mixing during

treatment and so forth Also if the microwave disinfestationis made economical it may serve as a safe and effectivealternate method of insect control The most importantfactor in the development of an acceptable insect controlmethod using microwave energy is to identify a balancebetween minimized thermal impact on the product qualityand complete killing of the insect population To achieve abalance between complete eradication of the insects and tomaintain the product quality further research needs to bedone on large scale tests with infested product to confirm thetreatment efficacy and product quality after extended storagebefore this technology would provide an acceptable processfor disinfestation

Acknowledgment

The authors acknowledge the Department of Science andTechnology (DST) India for providing financial support forthis study

References

[1] S Lal and B P Srivastava ldquoInsect pests of stored wheat ofMadhya Pradesh (India)rdquo Journal of Entomological Researchvol 9 pp 141ndash148 1985

[2] A K Sinha and K K Sinha ldquoInsect pests Aspergillus flavusand aflatoxin contamination in stored wheat a survey at NorthBihar (India)rdquo Journal of Stored Products Research vol 26 no4 pp 223ndash226 1990

[3] B Subramanyam and DW HagstrumAlternatives to Pesticidesin STored-Product IPM Kluwer Academic Publishers NorwellMass USA 2000

[4] R I Sanchez-MarinEzMOCortez-Rocha FOrtega-DorameM Morales-Valdes and M I Silveira ldquoEnd-use quality of flourfrom Rhyzopertha dominica infested wheatrdquo Cereal Chemistryvol 74 no 4 pp 481ndash483 1997

[5] F S Nasab A A Pourmirza and A H Zade ldquoThe effectof microwave radiation with cold storage on the mortality ofIndian meal moth (Plodia Interpunctella Hub) Eggsrdquo PakistanJournal of Entomology vol 31 no 2 pp 111ndash115 2009

[6] J P Edwards J E Short and L Abraham ldquoLarge-scale evalu-ation of the insect juvenile hormone analogue fenoxycarb as along-termprotectant of storedwheatrdquo Journal of Stored ProductsResearch vol 27 no 1 pp 31ndash39 1991

[7] Y Rajashekar N Bakthavatsalam and T ShivanandappaldquoReview article on botanicals as grain protectantsrdquo vol 2012Article ID 646740 13 pages 2012

[8] S Rajendran and V Sriranjini ldquoPlant products as fumigantsfor stored-product insect controlrdquo Journal of Stored ProductsResearch vol 44 no 2 pp 126ndash135 2008

[9] FDA Food Drug Administration Wheat Flour-AdulterationWith Insect Fragments and Rodent Hairs (CPG 7104 06)Compliance Policy Guides Manual chapter 5 Foods color andcosmetics sub chapter 578-processed grain 1997

[10] FGIS Federal Grain Inspection Service Official United Statesstandards for grain subpart m United States standards forwheat 1999

[11] D B Pinniger M R Stubbs and J Chambers ldquoThe evaluationof some food attractants for the detection of Oryzaephilussurinamensis (L) and other storage pestsrdquo in Proceedings of


the 3rd International Working Conference on Stored ProductEntomology pp 640ndash650 Kansas USA October 1984

[12] R Vadivambal D S Jayas and N D White ldquoDisinfestation oflife stages of Tribolium castaneum in wheat using microwaveenergyrdquo in Proceedings of the CSBESCGAB 2006 AnnualConference Edmonton Alberta 2006 Paper No 06-120S

[13] E Mitcham ldquoQuarantine issues in 2000rdquoActa Horticulture vol553 pp 451ndash455 2001

[14] J Gannage ldquoPesticides and human healthrdquo 2000 httpwwwherbs2000comarticlespesticideshtm

[15] R N Sinha and F L Watters Insect Pests of Flour Mills GrainElevators and FeedMills andTheir Control AgricultureCanadaWinnipeg Canada 1985

[16] E J Bond Manual of Fumigation For Insect Control Food andAgricultural Organization Rome Italy 1984

[17] J G Leesch G F Knapp and B E Mackey ldquoMethyl bromideadsorption on activated carbon to control emissions fromcommodity fumigationsrdquo Journal of Stored Products Researchvol 36 no 1 pp 65ndash74 2000

[18] UNEP (United Nations Environment Programme) Report ofthe 9th Meeting of the Parties To the Montreal ProTocol onSubstances That Deplete the Ozone Layer UNEPOzLPro 912Montreal Canada 1997

[19] S Rajendran and NMuralidharan ldquoPerformance of phosphinein fumigation of bagged paddy rice in indoor and outdoorstoresrdquo Journal of Stored Products Research vol 37 no 4 pp351ndash358 2001

[20] C H Bell and S M Wilson ldquoPhosphine tolerance and resis-tance in Trogoderma granarium Everts (Coleoptera Dermesti-dae)rdquo Journal of Stored Products Research vol 31 no 3 pp 199ndash205 1995

[21] B H Subramanyam and D Hagstrum ldquoResistance measure-ment and managementrdquo in Integrated Management of Insects inStored Products B Subramanyam and D Hagstrum Eds pp331ndash398 Marcel Dekker New York NY USA 1995

[22] P Collins G Daglish H Pavic T Lambkin R Kopittkeand B Bridgeman ldquoCombating strong resistance to phosphinein stored grain pests in Australiardquo in Proceedings of the 2ndAustralian Postharvest Technical Conference E J Wright HJ Banks and E Highley Eds pp 109ndash112 Adelaide SouthAustralia 2000

[23] S J Langlinais ldquoEconomics of microwave treated rice forcontrolling weevilsrdquo ASAE Paper 893544 ASABE St JosephMich USA 1989

[24] E Shadia and S E Abd El-Aziz ldquoControl strategies of storedproduct pestsrdquo Journal of Entomology vol 8 no 2 pp 101ndash1222011

[25] P G Fields and W E Muir ldquoPhysical controlrdquo in IntegratedManagement of Insects in Stored Products Marcel Dekker NewYork NY USA 1996

[26] J Banks and J B Fields ldquoPhysical methods for insect controlin stored-grain ecosystemsrdquo in Stored-Grain Ecosystem D SJayas N D GWhite andW E Muir Eds pp 353ndash410 MarcelDekker New York NY USA 1995

[27] M Hasan and A R Khan ldquoControl of stored-product pests byirradiationrdquo Integrated Pest Management Reviews vol 3 no 1pp 15ndash29 1998

[28] S Wang and J Tang ldquoRadio frequency and microwave alter-native treatments for insect control in nuts A reviewrdquo Interna-tional Agricultural Engineering Journal vol 10 no 3-4 pp 105ndash120 2001

[29] G Saour and H Makee ldquoSusceptibility of potato tuber moth(Lepidoptera Gelechiidae) to postharvest gamma irradiationrdquoJournal of Economic Entomology vol 97 no 2 pp 711ndash714 2004

[30] N W Heather G Hallman and N Heather Pest Managementand Phytosanitary Trade Barriers CABi Publishing CambridgeMass USA 2008

[31] M Gao J Tang Y Wang J Powers and S Wang ldquoAlmondquality as influenced by radio frequency heat treatments fordisinfestationrdquo Postharvest Biology and Technology vol 58 no3 pp 225ndash231 2010

[32] S O Nelson P G Hartley and K C Lawrence ldquoRF andmicrowave dielectric properties of stored-grain insects andtheir implications for potential insect controlrdquo Transactions ofthe American Society of Agricultural Engineers vol 41 no 3 pp685ndash692 1998

[33] R Vadivambal Disinfestation of Stored Grain Insects UsingMicrowave Energy [PhD thesis] University of Manitoba Win-nipeg Canada 2009

[34] M S Venkatesh and G S V Raghavan ldquoAn overview ofmicrowave processing and dielectric properties of agri-foodmaterialsrdquo Biosystems Engineering vol 88 no 1 pp 1ndash18 2004

[35] M P Fakude ldquoEradication of storage insect pests inmaize usingmicrowave energy and the effects of the latter on grain qual-ityrdquo 2007 httpupetdupaczathesisavailableetd-01292009-131525unrestricteddissertationpdf

[36] P C Annis and R Morton ldquoThe acute mortality effects ofcarbon dioxide on various life stages of Sitophilus oryzaerdquoJournal of Stored Products Research vol 33 no 2 pp 115ndash1241997

[37] N Gunasekaran and S Rajendran ldquoToxicity of carbon dioxideto drugstore beetle Stegobium paniceum and cigarette beetleLasioderma serricornerdquo Journal of Stored Products Research vol41 no 3 pp 283ndash294 2005

[38] D E Evans ldquoSome biological and physical constraints to theuse of heat and cold for disinfesting and preserving storedproductsrdquo in Proceedings of the 4th International WorkingConference of Stored Product Protection E Donahaye and SNavarro Eds pp 149ndash164 Tel-Aviv Israel 1986

[39] J L Sharp J J Gaffney J I Moss and W P Gould ldquoHot-airtreatment device for quarantine researchrdquo Journal of EconomicsEntomology vol 84 pp 520ndash527 1991

[40] P G Fields ldquoThe control of stored-product insects and miteswith extreme temperaturesrdquo Journal of Stored Products Researchvol 28 no 2 pp 89ndash118 1992

[41] V Y Yokoyama G T Miller and R V Dowell ldquoResponse ofcodling Moth (Lepidoptera Tortricidae) to high temperaturea potential quarantine treatment for exported commoditiesrdquoJournal of Economics Entomology vol 84 pp 528ndash531 1991

[42] L G Neven ldquoCombined heat treatments and cold storageeffects on mortality of fifth-instar codling moth (LepidopteraTortricidae)rdquo Journal of Economic Entomology vol 87 no 5 pp1262ndash1265 1994

[43] L G Neven and L M Rehfield ldquoComparison of Pre-StorageHeat Treatments on Fifth-Instar Codling Moth (LepidopteraTortricidae)Mortalityrdquo Journal of Economic Entomology vol 88pp 1371ndash1375 1995

[44] L J Mason and C A Strait ldquoStored product integrated pestmanagement with extreme temperaturesrdquo in Temperature Sen-sitivity in Insects andApplication in Integrated PestManagementG J Hallman and D L Denlinger Eds pp 141ndash177 WestviewPress Boulder Colo USA 1998


[45] A K Dowdy ldquoHeat sterilization as an alternative to methylbromide fumigation in cereal processing plantsrdquo in Proceedingsof 7th International Working Conference for Stored ProductProtection Z Jin Q Liang Y Liang X Tan and L Guan Edspp 1089ndash1095 Beijing China 1999

[46] C S Burks J A Johnson D E Maier and J W HeapsldquoTemperaturerdquo in Alternatives to Pesticides in stored ProductIPM B Subramanyam and D W Hagstrum Eds pp 73ndash104Kluwer Academic Publishers Boston Mass USA 2000

[47] J Tang J N Ikediala S Wang J D Hansen and R P CavalierildquoHigh-temperature-short-time thermal quarantine methodsrdquoPostharvest Biology and Technology vol 21 no 1 pp 129ndash1452000

[48] S Wang J N Ikediala J Tang et al ldquoRadio frequency treat-ments to control codling moth in in-shell walnutsrdquo PostharvestBiology and Technology vol 22 no 1 pp 29ndash38 2001

[49] S Wang J Tang and R P Cavalieri ldquoModeling fruit internalheating rates for hot air and hot water treatmentsrdquo PostharvestBiology and Technology vol 22 no 3 pp 257ndash270 2001

[50] S Lurie T Jemric A Weksler R Akiva and Y Gazit ldquoHeattreatment of rsquoOroblancorsquo citrus fruit to control insect infesta-tionrdquo Postharvest Biology and Technology vol 34 no 3 pp 321ndash329 2004

[51] M Schirra M Mulas A Fadda I Mignani and S LurieldquoChemical and quality traits of ldquoOlindardquo and ldquoCampbellrdquooranges after heat treatment at 44 or 46∘C for fruit fly disinfes-tationrdquo LWTmdashFood Science and Technology vol 38 no 5 pp519ndash527 2005

[52] O Dosland B Subramanyam K Sheppard and R MahroofldquoTemperature modification for insect controlrdquo in Insect Man-agement For Food Storage and Processing J Heaps Ed pp 89ndash103 American Association of Cereal Chemists St Paul MinnUSA 2005

[53] S J Beckett P G Fields and B Subramanyam ldquoDisinfestationof stored products and associated structures using heatrdquo inHeat Treatments For Postharvest Pest Control Theory andPractice J Tang E Mitcham S Wang and S Lurie Eds CABInternational Wallingford UK 2006

[54] O Dosland B Subramanyam K Sheppard and R MahroofldquoTemperature modification for insect controlrdquo in Insect Man-agement For Food Storage and Processing J Heaps Ed pp89ndash103 American Association for Clinical Chemistry St PaulMinn USA 2nd edition 2006

[55] E J Mitcham S Zhou and V Bikoba ldquoControlled atmospheresfor quarantine control of three pests of table graperdquo Journal ofEconomic Entomology vol 90 no 5 pp 1360ndash1370 1997

[56] R W Howe ldquoA summary of estimates of optimal and minimalconditions for population increase of some stored productsinsectsrdquo Journal of Stored Products Research vol 1 no 2 pp177ndash184 1965

[57] J Hansen ldquoHeating curve models of quarantine treatmentsagainst insect pestsrdquo Journal of Economics Entomology vol 85pp 1846ndash1854 1992

[58] S Lurie ldquoPostharvest heat treatmentsrdquo Postharvest Biology andTechnology vol 14 no 3 pp 257ndash269 1998

[59] S Wang X Yin J Tang and J D Hansen ldquoThermal resistanceof different life stages of codling moth (Lepidoptera Tortrici-dae)rdquo Journal of Stored Products Research vol 40 no 5 pp 565ndash574 2004

[60] G J Hallman J J Gaffney and J L Sharp ldquoVapor heat treat-ment for grapefruit infested with Caribbean fruit fly (Diptera

Tephritidae)rdquo Journal of Economic Entomology vol 83 no 4pp 1475ndash1478 1990

[61] D Ortega-Zaleta and E M Yahia ldquoTolerance and qualityof mango fruit exposed to controlled atmospheres at hightemperaturesrdquo Postharvest Biology and Technology vol 20 no2 pp 195ndash201 2000

[62] K C Shellie R L Mangan and S J Ingle ldquoTolerance ofgrapefruit and mexican fruit fly larvae to heated controlledatmospheresrdquo Postharvest Biology and Technology vol 10 no2 pp 179ndash186 1997

[63] E L Kerbel G Mitchell and G Mayer ldquoEffect of postharvestheat treatment for insect control on the quality and market lifeof avocadosrdquo Horticultural Science vol 22 pp 92ndash94 1987

[64] K J Smith andM Lay-Yee ldquoResponse of ldquoRoyal Galardquo apples tohot water treatment for insect controlrdquo Postharvest Biology andTechnology vol 19 no 2 pp 111ndash122 2000

[65] D M Obenland M L Arpaia R K Austin and B E MacKeyldquoHigh-temperature forced-air treatment alters the quantity offlavor-related volatile constituents present in navel and valenciaorangesrdquo Journal of Agricultural and Food Chemistry vol 47 no12 pp 5184ndash5188 1999

[66] D B Thomas and K C Shellie ldquoHeating rate and inducedthermotolerance in Mexican fruit fly (diptera tephritidae)larvae a quarantine pest of citrus and mangoesrdquo Journal ofEconomic Entomology vol 93 no 4 pp 1373ndash1379 2000

[67] S J Beckett and RMorton ldquoMortality ofRhyzopertha dominica(F) (Coleoptera Bostrychidae) at grain temperatures rangingfrom 50∘C to 60∘C obtained at different rates of heating in aspouted bedrdquo Journal of Stored Products Research vol 39 no 3pp 313ndash332 2003

[68] S Wang and J Tang ldquoHeating uniformity and differentialheating of insects in almonds in radio frequency systemsrdquoPaper 076019 American Society of Agricultural and BiologicalEngineers St Joseph Mich USA 2007

[69] X Yin S Wang J Tang J D Hansen and S Lurie ldquoTher-mal conditioning of fifth-instar Cydia pomonella (LepidopteraTortricidae) affects HSP70 accumulation and insect mortalityrdquoPhysiological Entomology vol 31 no 3 pp 241ndash247 2006

[70] D E Evans G R Thorpe and T Dermott ldquoThe disinfestationof wheat in a continuous-flow fluidized bedrdquo Journal of StoredProducts Research vol 19 no 3 pp 125ndash137 1983

[71] Y C Fu ldquoFundamentals and industrial applications ofmicrowave and radio frequency in food processingrdquo in FoodProcessing Principles and Applications J S Smith and Y HHui Eds Blackwell Iowa City IA Iowa USA 2004

[72] M A Stuchly ldquoHealth effects of exposure to electromagneticfieldsrdquo IEEE Aerospace Applications Conf Proceeding vol 1 pp351ndash368 1995

[73] S O Nelson and J A Payne ldquoRF dielectric heating forpecan weevil controlrdquo Transactions of the American Society ofAgricultural Engineers vol 31 pp 456ndash458 1982

[74] D Andreuccetti M Bini A Ignesti A Gambetta and R OlmildquoMicrowave destruction of woodwormsrdquo Journal of MicrowavePower and Electromagnetic Energy vol 29 no 3 pp 153ndash1601994

[75] S O Nelson ldquoReview and assessment of radio-frequency andmicrowave energy for stored-grain insect controlrdquo Transactionsof the American Society of Agricultural Engineers vol 39 no 4pp 1475ndash1484 1996

[76] S Wang J N Ikediala J Tang and J D Hansen ldquoThermaldeath kinetics and heating rate effects for fifth-instar Cydia


pomonella (L) (Lepidoptera Tortricidae)rdquo Journal of StoredProducts Research vol 38 no 5 pp 441ndash453 2002

[77] S Wang J Tang J A Johnson and J D Hansen ldquoThermal-death kinetics of fifth-instarAmyelois transitella (Walker) (Lep-idoptera Pyralidae)rdquo Journal of Stored Products Research vol38 no 5 pp 427ndash440 2002

[78] SWang J Tang J A Johnson et al ldquoProcess protocols based onradio frequency energy to control field and storage pests in in-shell walnutsrdquo Postharvest Biology and Technology vol 26 no3 pp 265ndash273 2002

[79] E JMitchamRHVeltmanX Feng et al ldquoApplication of radiofrequency treatments to control insects in in-shell walnutsrdquoPostharvest Biology and Technology vol 33 no 1 pp 93ndash1002004

[80] F Marra L Zhang and J G Lyng ldquoRadio frequency treatmentof foods review of recent advancesrdquo Journal of Food Engineer-ing vol 91 no 4 pp 497ndash508 2009

[81] S Wang G Tiwari S Jiao J A Johnson and J TangldquoDeveloping postharvest disinfestations treatments for legumesusing radio frequency energyrdquo Biosystems Engineering vol 105no 3 pp 341ndash349 2010

[82] S Jiao J A Johnson J K Fellman et al ldquoEvaluating the storageenvironment in hypobaric chambers used for disinfesting freshfruitsrdquo Biosystems Engineering vol 111 no 3 pp 271ndash279 2012

[83] S Wang M Monzon J A Johnson E J Mitcham and JTang ldquoIndustrial-scale radio frequency treatments for insectcontrol in walnuts I Heating uniformity and energy efficiencyrdquoPostharvest Biology and Technology vol 45 no 2 pp 240ndash2462007

[84] S Wang M Monzon J A Johnson E J Mitcham and J TangldquoIndustrial-scale radio frequency treatments for insect controlin walnuts II Insect mortality and product qualityrdquo PostharvestBiology and Technology vol 45 no 2 pp 247ndash253 2007

[85] M C Lagunas-Solar Z Pan N X Zeng T D Truong R Khirand K S P Amaratunga ldquoApplication of radiofrequency powerfor non-chemical disinfestation of rough rice with full retentionof quality attributesrdquoApplied Engineering in Agriculture vol 23no 5 pp 647ndash654 2007

[86] S Wang J Tang R P Cavalieri and D C Davis ldquoDifferentialheating of insects in dried nuts and fruits associated withradio frequency andmicrowave treatmentsrdquo Transactions of theAmerican Society of Agricultural Engineers vol 46 no 4 pp1175ndash1182 2003

[87] S Wang J Tang J A Johnson et al ldquoDielectric propertiesof fruits and insect pests as related to radio frequency andmicrowave treatmentsrdquo Biosystems Engineering vol 85 no 2pp 201ndash212 2003

[88] S L Halverson R Plarre T S Bigelow and K Lieber ldquoRecentadvance in the use of EHF energy for the control of insect instored productsrdquo in Proceedings of the ASAE Annual Interna-tional Meeting Orlando Fla USA 1998 Paper No 986052

[89] J N Ikediala J Tang L G Neven and S R Drake ldquoQuarantinetreatment of cherries using 915 MHz microwaves temperaturemapping codling moth mortality and fruit qualityrdquo PostharvestBiology and Technology vol 16 no 2 pp 127ndash1 1999

[90] O A Karabulut and N Baykal ldquoEvaluation of the use ofmicrowave power for the control of postharvest diseases ofpeachesrdquo Postharvest Biology and Technology vol 26 no 2 pp237ndash240 2002

[91] F L Watters ldquoMicrowave radiation for control of Triboliumconfusum in wheat and flourrdquo Journal of Stored ProductsResearch vol 12 no 1 pp 19ndash25 1976

[92] M A K Hamid C S Kashyap and R V CauwenbergheldquoControl of grain insects by microwave powerrdquo Journal ofMicrowave Power vol 3 no 3 pp 126ndash135 1968

[93] S L Halverson T W Phillips T S Bigelow G N Mbata andM E Payton ldquoThe control of various species of stored-productinsects with EHF energyrdquo in Proceeding of the Annual Interna-tional Research Conference on Methyl Bromide Alternatives andEmissions Reductions pp 54-1ndash54-4 1999

[94] R V Decareau Microwaves in the Food Processing IndustryAcademic Press Natick Mass USA 1985

[95] P P Sutar and S Prasad ldquoMicrowave drying technology-recentdevelopments and RampD needs in Indiardquo in proceedings of the42nd ISAEAnnual Convention pp 1ndash3 Kolkata India February2008

[96] H Linn and M Moller ldquoMicrowave heatingrdquo in Proceedings ofthe Thermprocess Symposium pp 16ndash21 Dusseldorf GermanyJune 2003

[97] S O Nelson and S Trabelsi ldquoFactors influencing the dielec-tric properties of agricultural and food productsrdquo Journal ofMicrowave Power and Electromagnetic Energy vol 46 no 2 pp93ndash107 2012

[98] E W Tilton and H H Vardell ldquoCombination of microwavesand partial vacuum for control of four stored-product insectsin stored grainrdquo Georgia Entomological Society vol 17 pp 96ndash106 1982

[99] E W Tilton and J H Brower ldquoIonizing radiation for insectcontrol in grain and grain productsrdquo Cereal Foods World vol32 no 4 pp 330ndash335 1987

[100] N Shayesteh and N N Barthakur ldquoMortality and behaviourof two stored-product insect species during microwave irradia-tionrdquo Journal of Stored Products Research vol 32 no 3 pp 239ndash246 1996

[101] S S Bedi andM Singh ldquoMicrowaves for control of stored graininsectsrdquo National Academy of Science Letter vol 15 no 6 pp195ndash197 1992

[102] D Sanchez-Hernandez J V Balbastre and J M OscaldquoMicrowave energy as a viable alternative to methyl bromideand other pesticides for rice disinfection of industrial pro-cessesrdquo in Proceedings of International Conference on Alterna-tives toMethyl Bromide pp 159ndash162 Sevilla SpainMarch 2002

[103] W R Halverson T S Bigelow and S L Halverson ldquoDesign ofHigh-Power Microwave Applicator for the Control of Insectsin Stored Productsrdquo in Proceedings of the Annual InternationalMeeting pp 27ndash30 American Society for Agricultural Engi-neers Las Vegas Nev USA July 2003 Paper No 036156

[104] R Vadivambal D S Jayas and N D G White ldquoWheat dis-infestation using microwave energyrdquo Journal of Stored ProductsResearch vol 43 no 4 pp 508ndash514 2007

[105] R Vadivambal O F Deji D S Jayas and N D G White ldquoDis-infestation of stored corn using microwave energyrdquo Agricultureand Biology Journal of North America vol 1 no 1 pp 18ndash262010

[106] R Singh K K Singh and N Kotwaliwale ldquoStudy on disinfes-tation of pulses using microwave techniquerdquo Journal of FoodScience and Technology vol 49 no 4 pp 505ndash509 2012

[107] R Pande H N Mishra and M N Singh ldquoMicrowave dryingfor safe storage and improved nutritional quality of greengram seed (Vigna radiata)rdquo Journal of Agricultural and FoodChemistry vol 60 pp 3809ndash3816 2012

[108] S L HalversonW E Burkholder T S Bigelow E V Norsheimand M E Misenheimer ldquoHigh-power microwave radiation


as an alternative insect control method for stored productsrdquoJournal of Economic Entomology vol 89 no 6 pp 1638ndash16481996

[109] H H Webber R P Wangner and A G Pearson ldquoHighfrequency electric fields as lethal agents for insectsrdquo Journal ofEconomics Entomology vol 39 pp 481ndash498 1946

[110] S O Nelson ldquoDielectric properties of agricultural productsmeasurements and applicationsrdquo IEEE Transactions on Electri-cal Insulation vol 26 no 5 pp 845ndash869 1991

[111] S O Nelson ldquoRadio-frequency and microwave dielectric prop-erties of insectsrdquo Journal of Microwave Power and Electromag-netic Energy vol 36 no 1 pp 47ndash56 2001

[112] S O Nelson andW KWhitney ldquoRadiofrequency electric fieldsfor stored grain insect controlrdquo Transactions of the AmericanSociety of Agricultural Engineers vol 3 no 2 pp 133ndash137 1960

[113] S O Nelson L E Stetson and J J Rhine ldquoFactors InfluencingEffectiveness of Radiofrequency Electric Fields for Stored-Grain Insect Controlrdquo Transactions of the American Society ofAgricultural Engineers vol 9 pp 809ndash815 1966

[114] S O Nelson ldquoElectromagnetic Energyrdquo in Pest Control Biolog-ical Physical and Selected Chemical Methods WW Kilgore andR L Doutt Eds pp 89ndash145 Academic Press New York NYUSA 1967

[115] B Alfaifi J Tang B Rasco S Sablani and Y Jiao ldquoRadiofrequency disinfestation treatments for dried fruit dielectricpropertiesrdquo LWTmdashFood Science and Technology vol 50 no 2pp 746ndash754 2013

[116] J N Ikediala J Tang and T Wig ldquoA heating block system forstudying thermal death kinetics of insect pestsrdquo Transactions ofthe American Society of Agricultural Engineers vol 43 no 2 pp351ndash358 2000

[117] V M Rashkovan N A Khizhnyak A V Basteev L ABazyma LNino deRivera and I A Ponomaryova ldquoInteractionof electromagnetic waves with granular agricultural productand insectsrdquo Journal of Microwave Power and ElectromagneticEnergy vol 38 no 4 pp 1ndash12 2003

[118] J Tang ldquoDielectric Properties of foodsrdquo inMicrowave Processingof Foods H Schubert and M Regier Eds CRC Press Cam-bridge UK 2005

[119] A CMetaxas and R J Meredith Industrial Microwave HeatingPeter Peregrinus 1983

[120] G J Hallman and J L Sharp ldquoRadio Frequency Heat Treat-mentsrdquo in Quarantine Treatments For Pests of Food Plants J LSharp and G J Hallman Eds pp 165ndash170Westview Press SanFrancisco Calif USA 1994

[121] L E Campana M E Sempe and R R Filgueira ldquoPhysicalchemical and baking properties of wheat dried with microwaveenergyrdquo Cereal Chemistry vol 70 no 6 pp 760ndash762 1993

[122] M V Bhaskara Reddy G S V Raghavan A C Kushalappaand T C Paulitz ldquoEffect of microwave treatment on quality ofwheat seeds infected with Fusarium graminearumrdquo Journal ofAgricultural Engineering Research vol 71 no 2 pp 113ndash117 1998

[123] J Kaasova B Hubackova P Kadlec J Prihoda and Z OBubnik ldquoChemical and biochemical changes duringmicrowavetreatment of wheatrdquo Czech Journal of Food Science vol 20 pp74ndash78 2002

[124] M A K Hamid and R J Boulanger ldquoA new method forthe control of moisture and insect infestations of grain bymicrowave powerrdquo Journal of Microwave Power vol 4 no 1 pp11ndash18 1969

[125] D P Locatelli and S Traversa ldquoMicrowaves in the Control ofRice Infestantsrdquo Italian Journal of Food Science vol 1 no 2 p62 1989

[126] J L Sharp and R G McGuire ldquoControl of Caribbean fruit fly(Diptera Tephritidae) in navel orange by forced hot airrdquo Journalof Economic Entomology vol 89 no 5 pp 1181ndash1185 1996

[127] K C Shellie and R L Mangan ldquoDisinfestation effect of non-chemical treatments on market quality of fruitrdquo in PostharvestHandling of Tropical Fruits B R Champ Ed ACIAR Proceed-ings pp 304ndash310 1994

[128] J A Johnson K A Valero S Wang and J Tang ldquoThermaldeath kinetics of red flour beetle (Coleoptera Tenebrionidae)rdquoJournal of Economic Entomology vol 97 no 6 pp 1868ndash18732004

[129] K C Shellie and R L Mangan ldquoTolerance of red fleshedgrapefruit to a constant or stepped temperature forced-airquarantine heat treatmentrdquo Postharvest Biology and Technologyvol 7 no 1-2 pp 151ndash159 1996

[130] D R Wilkin and G Nelson Control of Insects in ConfectioneryWalnuts Using Microwaves vol 87 British Crop ProtectionCouncil Monograph Berks UK 1987

[131] A ZoubaO Khoualdia A AntoneoDiaferia V Valereo RositoH Bouabidi and B Chermiti ldquoMicrowave Treatment forPostharvest Control of the Date Moth Ectomyelois ceratoniaerdquoTunisian Journal of Plant Protection vol 4 no 2 pp 173ndash1832012

[132] S Ryynanen H Tuorila and L Hyvonen ldquoPerceived tempera-ture effects onmicrowave-heated meals andmeal componentsrdquoFood Service Technology vol 1 pp 141ndash148 2001

[133] D S Lee D Shin and K L Yam ldquoImprovement of temperatureuniformity in microwave-reheated rice by optimizing heatcoldcyclerdquo Food Service Technology vol 2 no 2 pp 87ndash93 2002

[134] N Sakai C Wang S Toba and M Watanabe ldquoAn analysisof temperature distributions in microwave heating of foodswith non-uniform dielectric propertiesrdquo Journal of ChemicalEngineering of Japan vol 37 no 7 pp 858ndash862 2004

[135] A Manickavasagan D S Jayas and N D G White ldquoNon-uniformity of surface temperatures of grain after microwavetreatment in an industrialmicrowave dryerrdquoDrying Technologyvol 24 no 12 pp 1559ndash1567 2006

[136] S Gunasekaran and H W Yang ldquoEffect of experimentalparameters on temperature distribution during continuous andpulsedmicrowave heatingrdquo Journal of Food Engineering vol 78no 4 pp 1452ndash1456 2007

[137] S S R Geedipalli V Rakesh and A K Datta ldquoModelingthe heating uniformity contributed by a rotating turntable inmicrowave ovensrdquo Journal of Food Engineering vol 82 no 3pp 359ndash368 2007

[138] A Manickavasagan D S Jayas and N D G White ldquoGermi-nation of wheat grains from uneven microwave heating in anindustrial microwave dryerrdquo Canadian Biosystems Engineeringvol 49 pp 323ndash327 2007

[139] J M Hill and M J Jennings ldquoFormulation of model equationsfor heating by microwave radiationrdquo Applied MathematicalModelling vol 11 pp 369ndash319 1993

[140] Z Songping Z Yinglong and T R Marchant ldquoA DRBEMmodel for microwave heating problemsrdquo Applied MathematicalModelling vol 19 no 5 pp 287ndash297 1995

[141] A Ayvaz and S Karaborklu ldquoEffect of cold storage and differentdiets on Ephestia kuehniella Zellerrdquo Journal of Pest Science vol81 no 1 pp 57ndash62 2008


[142] S Gasemzadeh A Pourmirza M Safaralizadeh and MMaroufpoor ldquoEffect of microwave radiation and cold storageon Tribolium castaneum Herbst (Coleoptera Tenebrionidae)and Sitophilus oryzae L (Coleoptera Curculionidae)rdquo Journalof Plant Protection Research vol 50 no 2 pp 140ndash145 2010

[143] O Valizadegan A A Pourmirza andMH Safaralizadeh ldquoTheimpact of microwaves irradiation and temperature manipula-tion for control of stored-products insectsrdquo African Journal ofBiotechnology vol 10 no 61 pp 13256ndash13262 2011

[144] S M El-Naggar and A A Mikhaiel ldquoDisinfestation of storedwheat grain and flour using gamma rays and microwaveheatingrdquo Journal of Stored Products Research vol 47 no 3 pp191ndash196 2011

[145] M Amjad andM Akbar Anjum ldquoEffect of gamma radiation ononion seed viability germination potential seedling growth andmorphologyrdquo Pakistan Journal of Agriculture vol 39 pp 202ndash206 2002

[146] N C Doty and C W Baker ldquoMicrowave conditioning of hardred spring wheat I Effects of wide power range on flour andbread qualityrdquo Cereal Chemistry vol 54 pp 717ndash727 1977

[147] S G Walde K Balaswamy V Velu and D G Rao ldquoMicrowavedrying and grinding characteristics of wheat (Triticum aes-tivum)rdquo Journal of Food Engineering vol 55 no 3 pp 271ndash2762002

[148] V Velu A Nagender P G Prabhakara Rao andD G Rao ldquoDrymilling characteristics of microwave dried maize grains (Zeamays L)rdquo Journal of Food Engineering vol 74 no 1 pp 30ndash362006

[149] R Vadivambal D S Jayas and N D G White ldquoMortality ofstored-grain insects exposed to microwave energyrdquo Transac-tions of the ASABE vol 51 no 2 pp 641ndash647 2008

[150] S O Nelson and L E Stetson ldquoPossibilities for vontrollinginsects with microwaves and lower frequency RF energyrdquo IEEETransactions on Microwave Theory and Techniques vol 22 no12 pp 1303ndash1305 1974

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

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International Journal of

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Zoology


Molecular Biology International

GenomicsInternational Journal of


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Hindawi Publishing Corporationhttpwwwhindawicom

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Stem CellsInternational



Enzyme Research



Microbiology


and grain product from the insect pests may amount to 20ndash30 in the tropical zone and 5ndash10 in the temperate zone [8]Food grain production in India has reached 250 million tonsin the year 2010-2011 in which nearly 20ndash25 food grainsare damaged by stored grain insect pests [7]With populationgrowth and the amount of cultivatable land shrinking grainlosses will continue to be a problem in the developing coun-tries Control of stored-product pests is one of themajor tasksbecause the damage inflicted to foodstuff is irreversible Alsowith progressive increase in the quantity of food grains andnecessity for longer storage periods these losses will escalateunless disinfestation measures are improved Internationalorganizations such as FDA [9] and FGIS [10] have set toler-ances and grade standards regulating the number of insectsand insect fragments above specified tolerances to makethe product illegal for human consumption In developedcountries even the mere presence of a few insects in a bulkat densities of considerably less than one insect per kg graincan cause a serious loss in itsmarket value In some developedcountries grain can be downgraded or rejected completely ifeven a single live insect is found [11]The efficient control andremoval of stored grain pests from food commodities havelong been the goal of entomologists throughout the worldVarious methods of insect control have been practiced tosave the grain In recent years technology has made markedprogress in the study of disinfestation of stored-grain insectsand of finding improved ways to control them especiallyto detect latent forms of infestation The implementation ofan insect-disinfestation method requires detailed analysis ofall the elements of an infestation problem the insects theirage species and distribution and their survival and develop-mental rates under different environmental conditions [12]Conventional chemicals grain protectants and fumigants areextensively used around the world to control insect pests instored commodities because of low cost fast processing andeasy application Greater regulation and restriction of methylbromide use will likely increase the cost of the fumigant aswell as reduce its availability [13] With the concerns abouthealth hazards of chemical pesticides and their resultingenvironmental pollution there is interest in developing alter-native nonchemical process protocol to control insect pestswhile retaining acceptable product quality These includeconventional hot air or water heating controlled atmosphereand dielectric heating (radio frequency (RF) and microwave(MW)) Currently the use of chemical fumigation remainswidespread and the efficient use of RF and MW methodsfor disinfestation is still in research stage The currentpaper reviews the various disinfestation methods of storedfood grains with special emphasis on recent advances inmicrowave disinfestation of stored food grains The principleof microwave disinfestation experimental results of qualitycharacteristics of microwave-treated grains and the chal-lenges of microwave disinfestation have also been described

2 Various Methods of Insect Control

The control of stored-product insects is very important ifthe quality of foodstuff is to be maintained The goal of

the control measure is to render the habitat unsuitable forthe growth and reproduction of stored-product insects Thefive major potential quarantine treatment methods used fordisinfestation of several insect pests for both the domesticand international markets are chemical fumigation ionizingradiation controlled atmosphere conventional hot airwaterheating and dielectric heating using radio frequency (RF)and microwave (MW) energy which have been described inthis paper

21 Chemical Method Since the 1950s chemical insecticideshave beenused extensively in grain storage facilities to controlstored-product insect pests due to low cost fast speed in pro-cessing and ease of use Most postharvest pest managementprograms therefore rely heavily on fumigants Currentlyover 25 million tons of chemicals worth over 30 billion USdollars are applied to crops in the world [14] The chemicalsused to control insects in the bulk stored-grains are composedof two classes namely contact insecticides and fumigantsContact insecticides such asmalathion chlorpyrifos-methylor deltamethrin are sprayed directly on grain or structureswhich provide protection from infestation for several months[15] Fumigants are gaseous insecticides applied to controlinsects in grains that are inaccessible by contact insecticideSome of the commonly used fumigants are methyl bromide(MeBr) and phosphine which rapidly kill all life stages ofstored-product insects in food product [16] Methyl bromideis now under the threat of withdrawal because it apparentlydepletes the Earthrsquos ozone layer [17] It has already beenestablished that the use of MeBr has led to serious envi-ronmental damage and hazards to peoplersquos health For thesereasons the Montreal Protocol constituted by the UnitedNations Environment Programme agreed on a phasing outof methyl bromide in the developed countries by 2005 andin the developing countries by 2015 [18] Phosphine has beenused as a replacement of methyl bromide for a long time[19] Conventional use of phosphine has failed frequently tocontrol insects [20] Another limiting factor is that insectsdevelop resistance to some particular chemical fumigantsSome of the contact insecticides have become ineffectivebecause of wide-spread resistance in insect populations Aworldwide survey of stored-product insects revealed that 87of 505 strains of the red flour beetle Tribolium castaneumcollected from 78 countries were resistant to malathion [15]Resistance to malathion is widespread in Canada USAand Australia [21] while resistance to phosphine is greatin Australia and India which may cause control failures[22] The other major problem associated with the chemicalmethods is that even if they are applied with care and inlimited quantity there is a possibility that these chemicalsmay remain in the food grains and have adverse effectson humans Fumigation often only kills live larvae or adultinsects but does not sterilize the eggs which are still alive inthe grain kernels [23] The consumption of organic productsis also increasing each year There is therefore interest indeveloping an alternative nonchemical process method tocontrol insect pests in food grains so as to minimize theenvironmental hazards associated with chemical insecticideswhile retaining acceptable product quality




2 003 CO

2 and 78


2known








2 Controlled









119901 = 21205871198642119891120576101584010158401205760119881 (1)









120576101584012057610158401015840120576101584012057610158401015840120576101584012057610158401015840120576101584012057610158401015840









120576lowast= 1205761015840minus 11989512057610158401015840 (2)








LethalDeath in days














3 Conclusion



Acknowledgment


References







































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology




2 003 CO

2 and 78


2known








2 Controlled









119901 = 21205871198642119891120576101584010158401205760119881 (1)









120576101584012057610158401015840120576101584012057610158401015840120576101584012057610158401015840120576101584012057610158401015840









120576lowast= 1205761015840minus 11989512057610158401015840 (2)








LethalDeath in days














3 Conclusion



Acknowledgment


References







































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology







119901 = 21205871198642119891120576101584010158401205760119881 (1)









120576101584012057610158401015840120576101584012057610158401015840120576101584012057610158401015840120576101584012057610158401015840









120576lowast= 1205761015840minus 11989512057610158401015840 (2)








LethalDeath in days














3 Conclusion



Acknowledgment


References







































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology




120576101584012057610158401015840120576101584012057610158401015840120576101584012057610158401015840120576101584012057610158401015840









120576lowast= 1205761015840minus 11989512057610158401015840 (2)








LethalDeath in days














3 Conclusion



Acknowledgment


References







































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology






LethalDeath in days














3 Conclusion



Acknowledgment


References







































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology










3 Conclusion



Acknowledgment


References







































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology




























































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology

review article microwave heating as an alternative...

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