the effect of pretreatment of ozone and citric acid on … najafi and shaban int. j. biosci. 2015...

98 Najafi and Shaban

Int. J. Biosci. 2015

RESEARCH PAPER OPEN ACCESS

The effect of pretreatment of ozone and citric acid on quality

of fresh-cut lettuce (Lettuce sativa L.) preserved into modified

atmosphere packaging (MAP)

Farzaneh Najafi*, Safoora Shaban

Department of Plant Scinece, Faculty of Biological Sciences, Kharazmi University, Tehran, Iran

Key words: Iceberg lettuce, microbial load, modified atmosphere, ozonated water.

http://dx.doi.org/10.12692/ijb/6.1.98-108

Article published on January 05, 2015

Abstract

In this study, the effect of three levels of citric acid (0, 0.5 and 1 g l-1) and three levels of ozonated water (0, 0.6

and 1 ppm) and the interaction of these two treatments on microbial load and qualitative features of fresh-cut

iceberg lettuce were studied. After treatment, microbial load and qualitative features of cut lettuce were

evaluated in modified atmosphere packaging (5% O2 + 5% CO2 + 90% N2) in four different storage times (3, 6, 9

and 12 days). The effects of these treatments were also compared with percidine (concentration 1 ml to 1200 ml

in water). After treatment, fresh-cut lettuce pieces were stored at 4C with relative humidity 75% for 12 days. The

results showed that the total count of microorganisms and the weight loss percentage were increased by

increasing the storage time, whereas parameters such as surface color, vitamin C and polyphenol oxidase activity

were decreased. In lettuces treated with different concentrations of citric acid, the lowest total count of

microorganisms was related to 1 g lˉ¹ citric acid concentration and also treatment with 1 ppm ozonated water

concentration. In total, treatments of citric acid and ozonated water, especially in high concentrations and

interaction of these treatments resulted in better preservation of qualitative features and reduced microbial load

of fresh-cut lettuces during storage time.

* Corresponding Author: Farzaneh Najafi [email protected]

International Journal of Biosciences | IJB |

ISSN: 2220-6655 (Print) 2222-5234 (Online)

http://www.innspub.net

Vol. 6, No. 1, p. 98-108, 2015

http://dx.doi.org/10.12692/ijb/6.1.98-108

mailto:[email protected]

http://www/



Introduction

There is a growing use of Modified Atmosphere

Packaging (MAP) today aimed to improve the quality

of freshly cut produce and to prolong shelf-life. The

use of this method for packaging freshly cut fruits and

vegetables helps preserve their quality and increase

their storage life (Artes et al., 2007). This method

reduces the respiration rate, the chemical and

biochemical reaction rates and the growth rate of

pathogenic microorganisms in freshly cut fruits and

vegetables and thus increases their shelf-life ( Coles et

al., 2009; Regaert et al., 2007).

A big issue presenting itself in the freshly-cut produce

industry is finding ways to reduce microbial

contamination and to maintain the reduction up to

the point when the consumer gets it to their mouth.

To reduce the microbial load of these produce,

various antimicrobial agents such as ozonated water

and organic acids are used. Using ozone is

recommended as an alternative to traditional

disinfectants due to its efficiency in low

concentrations and during short exposure times and

due to its way of decomposition into non-toxic

compounds. The antimicrobial action of ozone is due

to the strong oxidizing properties of ozone molecules

or the materials produced from its decomposition,

such as hydroxyl radicals, which rapidly react with

intracellular enzymes, nucleic materials and their cell

constituents, fungal spore coats or viral capsids

(Khadre et al., 2001). Organic acids, particularly

citrate, lactate, and acetate, have antimicrobial

properties (Artes et al., 2007). They are therefore

used to deactivate foodborne pathogens in fresh

produce. Organic acids act fast and destroy a wide

range of bacteria. Citric acid prevents the

discoloration of fruits and vegetables through its

inhibiting effects on the action of this enzyme; it is

therefore extensively used on freshly processed fruits

and vegetables (Olmez and Kretzschmar, 2009).

Many scientists have investigated the microbial-load-

reducing effect of antimicrobial agents such as

ozonated water and organic acids on the quality of

produce and found the highest total count of

microorganisms to pertain to bacteria, which are

often responsible for spoiled vegetables. Ozone is

known to change the permeability of bacterial cell

membrane and to destroy them. Akbas and Olmez,

2007 demonstrated that immersion treatment with

chlorine, citric acid and ozonated water effectively

helps reduce microflora in freshly cut iceberg lettuce,

and that immersion in organic acids has a greater

antimicrobial effect on lettuce microflora and storage

life compared to ozone or chlorine treatments (Akbas

and Olmez, 2007). In one study, researchers showed

that a combined ozone and citric acid treatment has a

greater effect on reducing the population of

pathogens in iceberg lettuce compared to single

treatments (Yuk et al., 2007). It's found that, when

using antimicrobial compounds, ozonated water has

great effects on destroying both gram positive and

gram negative bacteria in food (Restaino et al.,1995).

Immersion of iceberg lettuce in a 0.5% solution of

citric or lactic acid for 2 minutes can be as effective in

reducing microbial populations in freshly cut iceberg

lettuce as treatment with 100 ppm chlorine (Olmez

and Akbas, 2009).

Bacteria counts in spinach, lettuce and strawberry

treated with 0.05 ppm concentration of ozone and

stored at low temperatures for 7 days decreased by

30% to 50% (Kader et al., 1989). Salmonella

populations decreased in carrots treated with lemon

juice, vinegar and a combination of both (Sengun and

Karapinar, 2004). Uyttendaele et al., 2004 reported a

significant reduction in Psychrotrophic natural flora

in minimally-processed vegetables such as chopped

carrots, lettuce and pepper after treatment with a 2%

lactic acid for just 1 minute.

Being a salad vegetable, lettuce is consumed by a lot

of people. The present study thus investigated the

means of preserving the freshness of freshly cut

lettuce without sacrificing its nutritional quality and

also assessed the effect of proper doses of permitted

disinfectants (treatments with ozone and citric acid

separately and in combination) on increasing shelf

life and reducing microbial load of this produce for

supply to consumers.



Materials and methods

Iceberg lettuce was provided in the spring of 2011

from farms in Karaj and transferred to the cold

storage and stored for 24 hours at 4°C. Damaged and

unhealthy lettuce leaves were separated and the

remaining leaves were rinsed with water and when

the surface moisture dried, they were chopped

uniformly with a sharp knife and were kept in a cold

storage after treatment.

Treatments

In this study, fresh-cut lettuce pieces were immersed

in ozonated water treatment in three levels (0, 0.6

and 1 g l-1) for 10 minutes and in citric acid in three

levels (0, 0.5 and 1 g l-1) for 5 min. Then they were

packed using polypropylene package with modified

atmosphere of 5% O2 + 5% CO2 + 90% N2 and were

kept in the cold storage. In this study, a group of

fresh-cut lettuce was treated with percidine (by a ratio

of 1 to 1200) and considered sham group. An

ozonated water generator (Ozone EUF model

MHP1H) was used to produce ozonated water at

needed concentrations.

Packing

Two-hundred grams of chopped lettuce was packaged

using Henkelman vacuum packaging machine (model

200A) under modified atmosphere (5% O2 + 5% CO2

+ 90% N2). Then lettuce packages were moved to cold

storages at temperature of 4°C with relative humidity

75%. The treated lettuce was sampled to assess the

factors in four stages, each stage including three days

in the cold storage.

Evaluated characteristics

Weight Loss

In all samplings, the plant fresh weight was measured

by a balance with 0.1 g accuracy and was obtained by

the following formula and reported as weight loss

percent (Saini et al., 2001).

Weight loss percent =

×

100.

Discoloration

The discoloration during the storage time was

measured based on parameters L*, a*, and b* (degree

of color transparency) by using a chromameter

(Konica Minolta CR-403, Japan) and chroma (purity

of color) and hue were calculated from the following

formula (Bernalte et al., 2003).

h0 =

c = 1/2

Vitamin C

For measuring vitamin C, titration with iodine and

potassium iodide and starch solution was used. Five

ml filtered lettuce juice was mixed with 20 ml

distilled water, and 2 ml starch solution 1% was added

to it. The resulting solution was titrated with iodine

and potassium iodide and the value of vitamin C was

obtained by the following formula (Saini et al., 2001).

C = (0.88 × V) / 5 × 100.

Measurement of polyphenol oxidase activity

One gram of lettuce tissue was pulverized in a mortar

with 6 ml sodium phosphate buffer (pH 6.5) and 1 mg

polyvinylpyrrolidone and the resulting mixture was

centrifuged (12000 rpm, 4C, 20 min). The reaction

mixture contained 0.2 ml catechol in addition to 2.7

ml sodium phosphate buffer (0.1 M) plus 0.1 ml

extract. The absorption was read every 10 seconds for

100 seconds at wavelength 420 nm (Huang et al.,

2009).

Evaluation of microbial load

Microbial load was evaluated during storage time

once every three days.

Sample preparation methods

The sample was prepared under a sterile hood. First,

the surface of the package was cut with a sterile knife

and 10 g of the sample was taken with forceps and

placed in a sampling container containing 90 ml

sterile normal saline and the sampling container was

capped. The container was left for 10 minutes so that

microbial load of the plant could be transferred into

the solution. This container had a dilution of 1/10

with 90 ml of normal saline and 10 g of sample plant.

After ensuring homogeneity of the initial dilution of



1/10, serial dilutions were prepared according to

standard protocols (Microbiology of Food and Animal

Feeding Stuffs. No.8923).

Sterilization of culture medium and containers and

tools needed

After normal saline was prepared and weighed in

glass containers and test tubes, glass containers were

capped and test tubes were plugged with cotton, and

then tightly wrapped in aluminum foil. Also, when the

culture media were prepared, they were covered with

cotton and then wrapped tightly in aluminum foil.

After normal saline and the culture media were

prepared, they were sterilized with other equipment

in an autoclave at 121°C for 20 min.

Instructions for culturing and total count of

microorganisms

First, 1 ml of the dilutions (in this experiment, the

dilutions 1/100, 1/1000, 1/10000 were cultured) was

poured into the sterile empty plates by a sampler and

then 15-20 ml of nutrient agar culture medium

sterilized at temperature of 45-50°C was added to

sterile plate containing the desired dilution. After

solidification of the culture medium, the plates were

tightly sealed with parafilm and then the plates were

placed in an incubator upside down at 30°C for 72

hours. After 72 hours, the plates were removed from

the incubator, and the total colony counts, including

bacteria and molds on each plate were counted by

using the following formula (Microbiology of Food

and Animal Feeding Stuffs. No. 5272).

The number of colonies in one gram or one ml of the

sample (cfugˉ¹ or ml) = The total number of colonies

× 1/dilution × 1/volume used.

Experimental design and statistical analysis

A factorial experiment was designed with 3 replicates

in a completely random model. Data were analyzed by

SPSS software programs and the means were

compared with Duncan multiple range test at P≤0.05

level.

Results and discussion

Weight Loss

Weight loss percentage had an increasing trend with

increasing storage time (Fig. 2 and Fig. 3). The results

also show that among different concentrations of

citric acid, treatment of 0.5 g l1- acid had the lowest

weight loss percentage and among various

concentrations of ozone, the lowest weight loss

percentage was related to 1 ppm ozone concentration

(Fig. 1). Weight loss is very important as it is

associated with economic issues and generally weight

loss more than 5% can reduce the market value of

fruits and vegetables (Brown and Bourne, 2002). In

general, evaporation, transpiration and respiration of

products after harvest and imbalance of vapor

pressure in the product tissues and the air inside the

package lead to weight loss and more weight loss over

time (Baldwin et al., 1995). In addition to treatments,

propylene packaging and also the use of modified

atmosphere are the most important factors in

preventing weight loss. Less water vapor permeability

of the package causes less weight loss percentage (Esti

et al., 2002). Weight loss in the used propylene

packaging was small due to low permeability to water

vapor, no steam escapes and the relative increase of

humidity inside the package. The use of modified

atmosphere was also effective in preventing weight

loss (Serrano et al., 2005). Lettuce stored in

propylene packaging at 5C showed 28% weight loss

after 7 days of storage (Allende et al., 2004).

Fig. 1. The effect of interaction of ozone and citric

acid on weight loss of fresh-cut lettuce.

Hue (h0)

The amount of hue indicator decreased with

increasing storage time (Fig. 5 and Fig. 6). Also

treatment with citric acid and ozone led to better



maintenance of hue in storage time and treatment

with percidine compared to treatment with ozone and

citric acid showed smaller amounts of hue (Fig. 4).

The amount of hue represents the actual color

parameter which is obtained by calculation a* and b*.

Color analysis shows that immersion of fresh-cut

iceberg lettuce in chlorine, organic acids and

ozonated water does not have adverse effects on

lettuce color, however, changes in the color

parameters were associated with time as increased

value of a*, decreased value of b*, reduced green

pigments, decreased value of L* and the darkening of

color (Akbas and Olmez, 2007). According to Bolin et

al.,1991 reduction of chlorophyll in cells will increase

the value of a*. Reduced value of b* can be due to the

reduction of ß- carotene during the storage time

(Bolin et al., 1991). Results show that the reduction of

hue indicator during storage time occurred because of

discoloration (browning) of cuts due to enzymatic

activities.

Fig. 2. The effect of interaction of citric acid and

percidine in storage time (day) on weight loss of

fresh-cut lettuce.

Fig. 3. The effect of interaction of ozone and

percidine in storage time (day) on weight loss of

fresh-cut lettuce.

Color purity (chroma)

Purity of color decreased over storage time (Fig. 8 and

Fig. 9), which was relatively slow. Ozone treatment

resulted in better preservation of chroma during

storage time, whereas lower concentrations of citric

acid showed better color purity during the storage

time (Fig. 7).


acid on hue indicator.


percidine in storage time (day) on hue indicator.

Brightness of fresh-cut lettuce (L*)

The color brightness indicator decreased because of

increased storage time (days) (Fig. 11 and Fig. 12). In

treatments used, lower concentrations of citric acid

and ozone caused better preservation of the color

brilliance during storage time and with increasing

concentrations of citric acid and ozone the brightness

of fresh-cut lettuce colors was decreased (Fig. 10).

Decreased value of L* may indicate the formation of a

dark part in the product, which can be attributed to

oxidation of phenolic compounds and microbial

wastes in the product during storage time (Akbas and

Olmez, 2007).

L* indicator in the stored products shows brightness



of the color, and given that L* is reduced during

storage time, it can be concluded that over time the

surface color of fresh-cut lettuce darkens. The results

of this study are consistent with the results of Jandric

et al., 2010. According to this researcher, the

browning of cut surface due to enzymatic reactions

decreases the color brightness during storage time.


percidine in storage time (day) on hue indicator.


acid on color purity (chroma).

Vitamin C

The amount of vitamin C was reduced by increasing

storage time (Fig. 14 and Fig. 15) and in comparison

of treatments, 0.5 g lˉ¹ citric acid concentration and 1

ppm ozone preserved vitamin C better during storage

time (Fig. 13). Treatment with percidine was also

effective on vitamin C preservation after the other

treatments. One reason is that in the early days of

storage time, the amount of oxygen in the packaging

was higher and oxidation of ascorbic-citric acid

(vitamin C) was more than dehydroascorbic acid

citric. According to Agar et al. (1997), increased

concentration of carbon dioxide by more than 20%

can further destroy vitamin C. In this study, actually,

with the increase of storage time and product

respiration, levels of carbon dioxide are increased and

destroy vitamin C during storage time.


percidine in storage time (day) on color purity

(chroma).


percidine in storage time (day) on color purity

(chroma).

It is said that the cut made in fresh-cut products will

induce an increase in ethylene production and the

ethylene can stimulate other physiological processes

such as the degradation of vitamin C etc. (Kader,

1985).


acid on Brightness (L*).

According to Zhang et al., 2005, increased

concentration of ozone leads to better preservation of



vitamin C in fresh-cut celery. The reduced vitamin C

during storage time, especially under modified

atmosphere conditions was consistent with the results

of Beltran et al., 2005 and Zhang et al., 2005.


percidine in storage time (day) on Brightness (L*).


percidine in storage time (day) on Brightness (L*).


acid on vitamin C content.

Polyphenol oxidase activity

As can be seen in Fig.17 and Fig.18, the activity of the

polyphenol oxidase reduced over time and compared

with the applied treatments, citric acid concentrations

(0.5 and 1 g lˉ¹) to the concentration of zero had the

lowest enzyme activity. However, in terms of the

numerical comparison, concentration 0.5 g lˉ¹

showed the lowest activity. In ozone treatment, 1 ppm

ozone concentration showed the lowest activity of

polyphenol oxidase during storage time (Fig. 16).

Enzymatic browning that can cause discoloration in

fruits and vegetables is the result of the activity of a

group of enzymes especially polyphenol oxidase that

has been reported in many plants. The results of

Zhang et al.,2005 showed that polyphenol oxidase

activity is reduced by treatment with ozonated water,

and higher concentrations of ozonated water have

more inhibitory effects on the activity of polyphenol

oxidase. The results of the present study are

consistent with the results of these researchers.


percidine in storage time (day) on vitamin C content.

The results of the present study is consistent with the

results obtained by Rico et al., 2006 who found that

ozonated water (1 mg l-1 at 18-20°C) on fresh-cut

lettuce leads to enzymatic and non-enzymatic

browning.


percidine in storage time (day) on vitamin C content.

Total count of microorganisms

As can be seen in Fig. 19, among different

concentrations of ozone, 1 ppm ozone concentration,



and among different concentrations of acid, 1 g lˉ¹

acid concentration had the greatest decrease in the

total count of microorganisms. Also, among the

interaction of different concentrations of citric acid

and ozone, the greatest decrease was related to the

interaction of 1 ppm ozone concentration in 1 g lˉ¹

citric acid. Total count of microorganisms is increased

over time (Fig. 20 and Fig. 21).


acid on polyphenol oxidase (PPO) activity.


percidine in storage time (day) on polyphenol oxidase

activity.

The highest total count of microorganisms was

related to bacteria that usually spoil vegetables. Most

of these bacteria are gram-negative bacteria especially

Erwinia and Pseudomonas that destroy the tissue of

these products (Barriga et al., 1991). The results of

this study are consistent with the results of Akbas and

Olmez, 2007.

Zambre et al., 2010 in their study found that

treatment with ozone on tomatoes can reduce the

microbial load and increase the shelf life of tomatoes.

Ketteringham et al., 2006 also showed the reduction

of microbial population treated with ozonated water

on cut green pepper.


percidine in storage time (day) on polyphenol oxidase

activity.


acid on total count of microorganisms.


percidine in storage time (day) on total count of

microorganisms.


percidine in storage time (day) on total count of

microorganisms.



Francis and O'Beirne (2002) found that the solution

of 1% citric acid for 5 minutes can reduce mesophilic

bacteria on lettuce about 1.5 log CFU gˉ¹.

Conclusion

The results showed that the total count of

microorganisms and weight loss percentage were

increased by increasing the storage time, while

parameters such as surface color, vitamin C and

polyphenol oxidase activity were decreased. Among

the different concentrations of citric acid, the highest

preservation of vitamin C was related to 0.5 g lˉ¹

citric acid concentration. In treatment with different

levels of ozonated water, the highest preservation of

vitamin C was related to the treatment with 1 ppm

ozonated water concentration. In the lettuce treated

with different concentrations of citric acid, the lowest

total count of microorganisms was related to 1 g lˉ¹

citric acid concentration and also treatment with 1

ppm ozonated water concentration. In all treatments

used, the increased concentrations and the

interaction of these treatments resulted in better

preservation of qualitative features and reduced

microbial quality during storage time.

Acknowledgement

The authors thanks Dr. Y. Mostofi for his support and

guidance at Faculty of Agricultural Science and

Engineering of Tehran Univeristy, Karaj, Iran.

References

Agar T, Streif J, Bangerth F. 1997. Effect of high

CO2 and controlled atmosphere (CA) on the ascorbic

and dehydroascorbic acid content of some berry

fruits. Postharvest Biology and Technology 11(1), 47-

55.

http://dx.doi.org/10.1016/s09255214(97)01414-2

Akbas MY, Olmez H. 2007. Effectiveness of

organic acid, ozonated water and chlorine dippings on

microbial reduction and storage quality of fresh-cut

iceberg lettuce. Journal of the Science of Food and

Agriculture 87(14), 2609-2616.

http://dx.doi.org/10.1002/jsfa. 3016

Allende A, Luo Y, McEvoy J, Artes F, Wang CY.

2004. Microbial and quality changes in minimally

processed baby spinach leaves stored under super

atmospheric oxygen and modified atmosphere

conditions. Postharvest Biology and Technology 33

(1), 51–59.

http://dx.doi.org/10.1016/j.postharvbio.2004.03.003

Artes F, Gomez PA, Artes-Hernandez F. 2007.

Physical, physiological and microbial deterioration of

minimally fresh processed fruits and vegetables. Food

Science and Technology International 13(3), 177–

188.

http://dx.doi.org/10. 1177/1082013207079610

Baldwin EA, Nisperos-Carriedo MO, Baker

RA. 1995. Edible coatings for lightly processed fruits

and vegetables. HortScience 30(1), 35–38.

Barriga MI, Trachy G, Willemot C, Simard RE.

1991. Microbial changes in shredded Iceberg lettuce

stored under controlled atmospheres. Journal of Food

Science 56(6), 1586-1588.

http://dx.doi.org/10.1111/j.13652621.1991.tb08646.x

Beltran D, Selma MV, Marin A, Gil MI. 2005.

Ozonated water extends the shelf life of fresh-cut

lettuce. Journal of Agricultural and Food Chemistry

53(14), 5654- 5663.

http://dx.doi.org/10.1021/jf050359c

Bernalte MJ, Sabio E, Hernandez MT,

Gervasini C. 2003. Influence of storage delay on

quality of ‘Van’ sweet cherry. Postharvest Biology and

Technology 28(2), 303-312.

http://dx.doi.org/10.1016/s09255214(02)00194-1

Bolin HR, Stafford AE, King ADJ, Huxsoll CC.

1991. Factors affecting the storage stability of

shredded lettuce. Journal of Food Science 42(5),

1319-1321.

http://dx.doi.org/10.1111/j.13652621.1977. tb14487.x

Brown SK, Bourne MC. 2002. Assessment of

components of fruit firmness in selected sweet cherry

http://dx.doi.org/10.1016/s09255214(97)01414-2

http://dx.doi.org/10.1002/jsfa.%203016

http://www.sciencedirect.com/science/article/pii/S0925521408002810#bbib11

http://dx.doi.org/10.1016/j.postharvbio.2004.03.003

http://dx.doi.org/10.%201177/1082013207079610

http://dx.doi.org/10.1111/j.13652621.1991.tb08646.x

http://dx.doi.org/10.1021/jf050359c

http://dx.doi.org/10.1016/s09255214(02)00194-1

http://dx.doi.org/10.1111/j.13652621.1977.%20tb14487.x



genotypes. HortScience 23, 902-904.

Coles R, McDowell D, Kirwan MJ. 2009. Food

Packaging Technology. Blackwell Publishing. CRC

Press. 368 P.

Esti M, Cinquanta L, Sinesio F, Moneta E,

Matteo MDi. 2002. Physicochemical and sensory

fruit characteristics of two sweet cherry cultivars after

cool storage. Food Chemistry 76(4), 399-405.

http://dx.doi.org/10.1016/s03088146(01)00231-x

Francis GA, O’Beirne D. 2002. Effects of vegetable

type and antimicrobial dipping on survival and

growth of Listeria innocua and E. coli. International

Journal of Food Science and Technolgy 37(6), 711–

718.

http://dx.doi.org/10.1046/j/13652621.2002.00622.x

Huang C, Yu B, Teng Y, Su J, Shu Q, Cheng Z,

Zeng L. 2009. Effects of fruit bagging on coloring

and related physiology, and qualities of red Chinese

sand pears during fruit maturation Scientia

Horticulturae Amsterdam 121(2), 149-158.

http://dx.doi.org/10.1016/j.scienta.2009.01.031

Jandric Z, Soliva-Fortuny R, Oms-Oliu G,

Martin-Belloso O, Grujic S. 2010. Effect of low

and superatmosferic O2 modified atmosphere on the

quality of fresh-cut pears. Applied Technologies and

Innovations 2(2), 29-39.

Kader AA. 1985. A summary of CA requirements

and Horticultural Science, North Carolina State Univ.

(USA) Raleigh, N. C. (USA).

Kader AA, Zagory D, Kerbel EL. 1989. Modified

atmosphere packaging of fruits and vegetables.

Critical Reviews in Food Science and Nutrition.

28(1), 1-30.

Ketteringham L, Gausseres R, James SJ,

James C. 2006. Application of aqueous ozone for

treating pre-cut green peppers (Capsicum annuum

L.). Journal of Food Engineering 76(1), 104–111.

http://dx.doi.org/10.1016/j.jfoodeng.2005.05.019

Khadre MA, Yousef AE, Kim JG. 2001.

Microbiological aspects of ozone applications in food:

a review. Journal of Food Science 66(9), 1242–1252.

http://dx.doi.org/10.1111/j.1365-2621.2001.tb15196.x

Microbiology of Food and Animal Feeding

Stuffs. No. 5272. Horizontal method for the

enumeration of microorganisms colony-count

technique at 30 ºC. Institute of Standards and

Industrial Research of Iran. 1387.

Microbiology of Food Animal Feeding Stuffs.

No. 8923.Methods for the preparation of test

samples, initial suspensions and decimal dilutions for

microbiological examination. Institute of Standards

and Industrial Research of Iran. 1387.

Olmez H, Akbas MY. 2009. Optimization of ozone

treatment of fresh-cut green leaf lettuce. Journal of

Food Engineering 90(4), 487–494.


Olmez H, Kretzschmar U. 2009. Potential

alternative disinfection methods for organic fresh-cut

industry for minimizing water consumption and

environmental import. Lwt- Food Science and

Technology 43(3), 686- 693.

http://dx.doi.org/10. 1016/j.lwt.2008.08.001

Regaert P, Devlieghere F, Debevere J. 2007.

Role of microbiological and physiological spoilage

mechanisms during storage of minimally processed

vegetables. Postharvest Biology and Technology.

44(3), 185- 194.

http://dx.doi.org/10.1016/j.postharvbiol.2007.01.001

Restaino L, Frampton EW, Hemphill JB,

Palnikar P. 1995. Efficacy of ozonated water against

various food-related microorganisms. Applied and

Environmental Microbiology 61(9), 3471–3475.

Rico D, Martin-Diana AB, Henehan G, Frias

JM, Henehan G, Barry-Ryan C. 2006. Effect of

http://dx.doi.org/10.1016/s03088146(01)00231-x

http://dx.doi.org/10.1046/j/13652621.2002.00622.x

http://dx.doi.org/10.1016/j.scienta.2009.01.031


http://dx.doi.org/10.1111/j.1365-2621.2001.tb15196.x


http://dx.doi.org/10.%201016/j.lwt.2008.08.001

http://dx.doi.org/10.1016/j.postharvbiol.2007.01.001





ozone and calcium lactate treatments on browning

and textured properties of fresh-cut lettuce. Journal

of Science Food and Agriculture 86(13), 2179–2188.

http://dx.doi.org/10.1002/jsfa.2594

Saini RS, Dhankhar OP, Sharma KD, Kaushik

RA. 2001. Laboratory Manual of Analytical

Techniques in Horticulture. Agrobios (India). 1st. Ed.

Pages. 135 P.

Sengun IY, Karapinar M. 2004. Effectiveness of

lemon juice, vinegar and their mixture in the

elimination of Salmonella typhimurium on carrots

(Daucus carota L.). International Journal of Food

Microbiology 96(3), 301- 305.

Serrano M, Martinez- Romero D, Castillo S,

Guillen F, Valero D. 2005. The use of natural

antifungal compounds improves the beneficial effect

of MAP in sweet cherry storage. Innovative Food

Science and Emerging Technologies 6(1), 115-123.

http://dx.doi.org/10.1016/j.ifset.2004.09.001

Uyttendaele M, Neyts K, Vanderswalmen H,

Notebaert E, Debevere J. 2004. Control of

aeromonas on minimally processed vegetables by

decontamination with lactic acid, chlorinated water,

or thyme essential oil solution. International Journal

of Food Microbiology 90(3), 263- 271.

http://dx.doi.org/10.1016/S0168-1605(03)00309-x

Yuk HG, Yoo MY, Yoon JW, Marshall DL, Oh

DH. 2007. Effect of combined ozone and organic acid

treatment for control of Escherichia coli O157:H7 and

Listeria monocytogenes on enoki mushroom. Food

Control 18(5), 548- 553.

http://dx.doi.org/10.1016/j.foodcont.2006.01.004

Zambre SS, Venkatesh KV, Shah NG. 2010.

Tomato redness for assessing ozone treatment to

extend the shelf life. Journal of Food Engineering

96(3), 463–468.

http://dx.doi.org/org/10.1016/j.jfoodeng.2009.08.02

7

Zhang L, Lu Z, Yu Z, Gao X. 2005. Preservation of

fresh-cut celery by treatment of ozonated water, Food

Control 16(3), 279–283.


http://dx.doi.org/10.1002/jsfa.2594

http://dx.doi.org/10.1016/j.ifset.2004.09.001

http://dx.doi.org/10.1016/S0168-1605(03)00309-x





the effect of pretreatment of ozone and citric acid on … najafi and shaban int. j. biosci. 2015...

Documents