1176

TJI._

INSTRUMENTATION

A laboratory continuous deodorizer

Various methods have beenused to remove volatilesfrom nonvolatile materials,

including techniques such as thin-film molecular distillation, steamdistillation, and vacuum distillation.

To remove the volatile compo-nents of fats and oils from the non-volatile triglycerides, a combinationof steam and vacuum distillation hasbeen used. a process that is referredto as steam deodorization. Such asystem can be batch, sermccnunuousor continuous. In most laboratories.only batch systems have been usedwhere the oil is heated to an elevatedtemperature for long periods of time.Steam is allowed to pass through theoil. and vacuum is used to reduceoxidation and to enhance the distil-lation of low-vapor pressure compo-nents, such as Iauy acids and otherhigh molecular weight materials.

The typical values that are usedto deodorize oils in a batch systemare shown in Table I. Today. a mod-ern oil refinery uses either a semi-continuous column or a truly contin-uous column to deodorize vegetableoils. Some of the suppliers of suchequipment and their general workingvariables are listed in Table 2.

Commercial deodorizers haveeither bubble trays or holding com-partments where the oil and steamare in contact with each other at vac-uums ranging from 3 to 15 torr

'J"'IW ~r origiMJJy wcu p~ptJJWJfor ddiwrydorio, dw 21n _ COllI"" ofdwlnummiDMI

Sociny fo,Fill Re_ dItIl "'" It<Id doriog1995in 7Jw Hape. 1Jae N~therlads. "1"M tuUIror.

dw /QuI no-.. H.s-.s. of A.m., o..u.bMidUJNI(_'I11noU~ dIAl".,.,. dw

COIffImt« MU Ittld. T1w ptIpIr sflbMqwntlyWAf rwMl by Dr. s...o...·s coIi«rrw at ADM. T1tomtu

JWimJ< dorio, tit< 1996AOCS ANuIaI Muting &Expo. AI" tIw tlCCepltJIICI kt:tMn for 1M

StqIwn S. CIttmg Awani dItIl ..... p,._".,.,-." to Dr. _ at dItIl....,.".

Table 1Typical condition tor a batchdeodorizer

Pump vacuumCondenser vacuumStearn usageTemperaturelime

O.QIlorr1.00lorr

3-,..180-26O"C

2-4 h

Table 2 Table 3Vartables of several commercial deodorizers Typical conditions

for the laboratoryHead Working continuous deodorizer

Hold limes pressure temperatureTray, (min) (torr) ("C)

Oil rate 600-2.500 mllhEMI 8 60 3 280 Steam rate 1.3-12.1%Wurster & Sanger 6 60 6 23. Oil temperature 8O-260°CExtraktionstechnik 4 4 2SS Residence time 6-9 minLurgi 12. 4 2SO Heal-up lime 5-10 secDeSmet 6 95-105 2 2S3 Cool-down time 15-30 secAI(a Laval 3 60 27S Bottom vacuum 10 lOfTG~~ 4 2 260 Top vacuum "~Krupp , I3S s 240 Pump vacuum 0.1 torrKirchfekl 2 90 3 260HLS , 3-, 2SO Cool-down exchanger 2O"'C

INFORM,VOl.8, no. II (November 199n

because of the pressure drop acrossthe compartments. With thisarrangement, a common residencetime may be 30-90 minutes. Semi-continuous deodorizers have beenused in some laboratories for a longtime. For example. Allen et al,described the bubble-cap type (Fig-ure I) in 1952. In this same paper,

he and his coworkers described theuse of a sieve plate Oldershaw col-umn (Figure 2). Dr. Stephen Chang,in 1961. described a countercurrentsteam deodorization apparatus (Fig-ure 3) that was used to remove theflavor from fats and oils. This paperdiscusses the LCD (laboratory con-tinuous deodorizer), shown in Figure4, with a sample of corn oil that isbeing deodorized with a steam rateof 2.5% and an oil rate of 600mLlhour. This apparatus can beexplained by the diagrammatic rep-resentation in Figure 5,

The oil to be deodorized is placedin a flask (A). By adjusting a Teflonneedle valve (C), the oil flow ratecan be adjusted and read from therotc meter (B). The oil is heatedwithin 5-10 seconds to the deodor-

1177

ization temperature by the statictube heat exchanger (D), which inturn is heated with electrical heatingtape connected to a voltage regula-tor. Air removal occurs in the alem-bic (E), which also prevents any

Figura 4. (Iatt) ADM laDoratory conlinuoull daodorl~er (LCD)FIgura 5. (below) Diagram of Iha LCD

•

•

condensed materials from flowingback to the distillation trays in col-umn (F). The air-condensed materi-als, such as free fatty acids. toco-pherols, pesticides, erc.. are collect-ed in trap (G), which is held at room

FIgura t. Schematic 01 bubble-elp .. mi-continuous cIeocIorlur

Figure 2. Schematk: rapr ... nlation 01Oldershaw' column

•

temperature. The more volatile fla-vor components are condensed incold traps (H, I) that are cooled withsolid carbon dioxide or liquid nitro-gen. The oil flowing down column(F) is stripped with steam that is

•• •

•,Figure 3. Counlan:urrenl steam deodor-ization apparetua

INFORM. VOl. 8. no. 11 (November 1997)

1178

INSTRUMENTATION

Figure 6. Oldershaw perforatadplata distiiialion column

umn, an injection port for antioxi-dants or sequestering agent, and afive-plate Oldershaw column.

An Oldershaw column (Figure 6)is a perforated plate distillation col-umn. Each plate is drilled with pre-cision holes for the vapor to passthrough and a downspout for the oilto move to the next lower plate. Fig-ure 7 provides a horizontal view ofthe plate, showing the weir thatadjusts the level of oil on the platebefore it overflows to the next lowerplate, and a top view of the perforat-ed plate with the precision-drilledholes.

To determine the oil temperatureduring deodorization, thermocouplewells are placed just above the sieveplates at the top, middle, and bottomof the columns. The column is sur-rounded with a Pyrex lube that is 5mm greater in diameter. This tube isheated with nichrome wire connect-

-,,((~- .

~ ' '-0

!.' 0:'"o 0 : • ~ 0• : • • • 0:.. :..o 0 '0 • o.

\0.;... •....:.:'0 °0 • 0 ••

0 o' .'....::.:::...

FIgure 7. Horizontal schematic ofOidellihaw column

generated in flask (J). The amountof steam is adjusted by anotherTenon needle valve (K) and mea-

-rne majority of my workconcerasllplds. manyofwltich posedcecuon problems, due to >'lU')'Ingor~bscnllN absorbance. Iprefer to3'oj)ldIheexlt:lSlcpofderh'lUil:l.Uon,which rules OUI fluorescence, andrefractive Index does nOI haveadequate scnsllMty. The EISDprcvidesa ~ryoon\'C!llem,sensitiveand reproducible deleclion methodfor a wide l'lIliety of compounds.All1ech·sFJ.SDsarc very con..:nlentto use, ~-e Infonn:Uil-e dlspLa~~,and need essenUaIJy110adjuSllIlenlfrom !lay to day, or ...eek to week.<h-er the las! two yean, I have IUUconsiderably more lh~n \11·0lhoosaIld s:amplesthrough myElSV.] lI"Ouida1so like to emphasize theaceIlenl quaJjryofseroiceand back·up I MVC had from jour company, aI"CI)' Importall\ faaor Iu purdwingan InstrumenL IIoIh forpromp!l1essIu shipping and qualiry of back ·up, Jhave to rate AlIlcch II of all thecomjT.lllles Idea[ ...im.-

-"fl.~ 1111&11, Ph.D.

sured with another rotometer (L).The deodorization column (F) con-sists of a ten-plate Oldershaw col-

Use the ELSDwithor without the £J'Afor OptimumResults for EveryApplication!

Alltech 500 ELSD Alone

• ExceUent Sensitivity forNon-volatile Ana!}1CS

• NearlyEquivalentResponse Factors forAll Sample Types

• More Sensitive than RIand Low-wavelengih LN

• Compatible with HPLC,GPC, and SFC

Alttec:h Associates, Ine.· 2051 Waukegan Road' Deerfield, IL 60015Toll Free: 1-800-255-8324' Phone: 847-948-8600' Fax: 847-948-1078Email: aUteehOallteehmail.com' Website: http://www.alltaehwab.eom

INFORM,Vol. 8, no. 11 (November 1997)

For Information circle '130

The Alltech 500ELSD Plus the NewLow TemperatureAdaptor (LTA)-

o MaximumSensitivityfor Scmf-vclauleAna!}1CS

o Stable Baselines withAqueous MobilePh""

- Compatible whh HighMobile PhasePlowraies

- Easy Installation onAny Alltech 500 orvarex MKlIl ElSD._-

1179

Close-up photos of portions of the LCD

INFORM. Vol. 8. no. 11 (November 1997)

1180

peratures are measured with thermo-couples connected to a ten-positionthermocouple thermometer. Normalpoints that are measured are (a) theheat-up exchanger, (b) the inlet,middle, and exit of the first ten-plateOldershaw column, (e) the inlet andoutlet of the second Oldershaw col-umn, and (d) the steam vapor deliv-ery tube. Sialic tube heat exchangerswere made from Koch SMV mixingelements. An example of one ofthese highly efficient tube mixers,chiefly used for turbulent flow, isshown in Figure 8.

Four of these units were placedinside a 0.5" (outside diameter) SIStube. In the heat-up static mixer, thistube was wrapped with electricalheating tape and insulation to allowa temperature of 288°C 10 beobtained and maintained. For thecooldown mixer, the unit was water-jacketed, with the supply being the

INSTRUMENTATION

Figure 8. Koch SMV tube mixer

ed to a voltage regulator. To form anair space and to insulate thenichrome wire, this second tube issurrounded also with a Pyrex tube

which is 5 mm greater in diameterthan the second tube.

This combination of concentrictubes, nichrome wire, and air chan-nels makes the overall dimensions ofthe 15-plate deodorization column tobe 70 mm (outside diameter) x 107em. It is closed at both ends andsealed with silicone caulk. Thedeodorized oil is cooled to 20°C inless than 30 seconds with a statictube heat exchanger (M) connectedto a refrigerated water bath. It isheld under vacuum in flask N orremoved from the apparatus using alower pressure than in flask N.

The entire system from the twoTeflon needle valves is drawn to anegative pressure with a mechanicalvacuum pump at point O. Vacuummeasurements are made at the bot-tom and the top of the column withmercury manometers, and at thepump with a McLeod gauge. Tem-

For information circle .113

INFORM. Vol. 8. no. 11 (November 1997)

..... ,------------,110.0

10.e•• ~I..~".1 .....'

•.• L-L_---.JL_.L_-L_---.Jc....J10.0 20.0 30.0 40.0 10.0

ITUllIU.TlIt/lW1

Figure 9. Steam rate eaJibr.tIon curve

refrigerated water bath. The oil wascooled to room temperature in lessthan 30 seconds with this cooldownexchanger. Normal operating condi-lions for the deodorizer are given inTable 3.

Some of these are upper andlower values and depend upon therate of oil now. The actual condi-tions used can be varied easilybetween these limits to determinethe values that give the most effi-cient deodorization. Photographs onpage J 179 provide close-ups of theLCD.

Figure 9 shows the calibrationcurves for the steam rate; the oil rateis shown on Figure 10. The steam uti-lization rates are shown in Table 4.

Some of the applications of thisunit are to follow the effect uponcolor (Figure 14). The lightness, yel-lowness, and the total color differ-

ence from a white plate do notchange until temperatures around270°C are used.

Figure 12 shows where free fanyacids were stripped from the particu-lar corn oil under the conditionsused in this specific run. Any tem-perature lower than 138°C did notremove acids, while temperatures inexcess of 184°C did not improve therate tremendously.

The natural antioxidants can bestripped from the oil, and conjugateddienes can be formed at higher tem-peratures. Naturally, the removal ofantioxidants and the formation ofdienes will cause poorer oxidativestability at the higher temperatures.

The LCD has been used in theADM laboratory to predict plantproblems with deodorization equip-ment before they develop. especial-ly for evaluating heat-set colors,

Steam('I'I't%)

J.31.72 .s3.34.•e.77.78.•

t 1.412.179.0

004 ~::::::::=:::::=-10.0 ~ '"'\... I:.!,AUIII------.a.t....

CO<4O....,.- 10.0 /=- _

\..........

Figure 11. Eff.c:t of deodorization temperature on eolor removal

INfORM, Vol. 8. no. II (November 1997)

.....r-----------,

.10..1I01OIRiiM......

I... 100.0

104, .~tO•• 0'111U•• "' ...710.4LL__~ __~ __L_~L~~

100.0 200.0 JOO.O 400.0 100.0 100.0Of.. ItATllg/irIrI

figure 10. Oil IIIte c:.Jibratlon eurve

Table 4Steam utlllzationa

Rotometer reading(oIVsteam)150135125135150/50125150100/50ISO/IOO7515012511001251125IOCVIOO501125

II Calibn.ed wi.h com oil and lube N034-39. ,lassI1QU rOO' oil and SIS nOfl. rOO' $learn.

fatty-acid removal. and flavor devel-opment at deodorization tempera-tures.

~r------------------,

0.1' ~

Flgurw 12. Effect of deodorization temperature on free fatty add(FF"') removal

1181

1182

INSTRUMENTATION

IFSC's Mtntdeodonzer

Description of the IFSC minideodorizerThe fFSC Minideodorizer is a small-scale version of the industrial physicalrefining process for edible oils andfats. The unit is mounted on a 1.5 x1.3 meter frame constructed to accom-modate forklift handling. The deodor-izer is a self-contained unit. No steam-supply connections are needed. Steam,vacuum, and cooling of the condenserare all created through the electricalpower supply.

The basic principle involved inphysical refining is vacuum steam dis-tillation under high-temperature andhigh-vacuum conditions to removefree fauy acids. oxidation products,and other compounds that can impartan unpleasant odor to the oils. Duringthe process the oil is protected withnitrogen to avoid oxidation.

The unit includes a deodorizingprocess vessel with a heating element,a high-vacuum pump. a condenser andcooling system. and a water and nitro-gen dosing system (Table I).

Batch sizes may be 15 to 50 kilo-

V.K.S. ShukUo

This article is by V K.S. Shukla. director of the inter-national Food Science Centre (IFSC), p.o. Box 4-1,

Sonderskovvej 7. DK-8520 Lystrup. Denmark. wherethe minideodorizer described was developed.

grams of oil or fat. The oil or liquifiedfat is sucked into the vessel by meansof the established vacuum. Electricalheating is started using a 6 kw heatingelement located in the center of theprocessing vessel. The oil is agitatedand heated to approximately 150°C; itis protected against deterioration bythe continuous addition of nitrogenduring the heating cycle.

At 150°C. water dosing is startedand nitrogen addition is halted. Watercan be dosed automatically or manual-ly, and the deodorization temperatureadjusted. The water is instantly con-vened to steam at this high tempera-ture. which agitates the oil. This tur-bulence in the oil ensures good physi-cal contact of the steam with the oil.The temperature and water dosage are

INFORM. Vol. 8. no. 11 (November 1997)

Table 1Mlnldeodorlzer technical specifications

Deodorization process vesselT()(aJ volumeWorking volumeMaximum working temperatureHeating elementWater/steam flow rate

250 liters15--50 liters25O"C6 kilowau0-5 kg per hour

Water-dosing pumpNominal outputFrequencySpeed

0.09 kilowatt50 or 60 Hz1,360 rpm at 50Hz. or 1.100 rpm at 60 Hz

Cooling unilCooling capacity 3 kilowatt at evaporation temperature ofO"C and surrounding temperature

of 32"C3 kilowatt at an inlet temperature of 5"C and an outlet temperature of 2.5"CEvaporation capacity

Vacuum pumpMaximum differential pressureNominal working liquid flow rate(using water at l5"C as working liquid)

Motor power

250 mbar at 50 or 60 Hz

0.28 m3Jh2.35 kilowatt

maintained during deodorization. Thelength of time for deodorizationdepends on (a) how much polar mate-rial is to be removed, (b) the deodor-ization temperature. (c) the level ofwater dosage, and (d) the vacuumused under the given operating condi-lions.

Fatty acids, ketones, aldehydes,and other oxidation products, aswell as other compounds that could

water dosing is halted and nitrogenaddition begins. Circulation of cool-ing water is stopped at a temperatureof 50_60°C, and the vacuum pump isturned off. The vacuum is graduallyreleased by nitrogen addition, andthe oil can be pumped out of the ves-sel.

The fully refined oil will be brightand transparent and will have virtuallyno flavor or odor (Table 2). •

impart an unpleasant odor to the oil,are carried over with the steam andcondensed in II high-efficiencyrifled tube and louvered fin coolingunit. At the end of the process, thecondensate is drained off the con-denser.

After the deodorization, the heat-ing is turned off and circulation ofcooling water begins. When the rem-perature has decreased to l50cC,

Table 2Results using camelina oil (highly triunsaturated oil) and confectionery palmoil-based specialty fat

Camelina oil Specialty futAmount 25 kg 11 kgTime 2 hours 2 hoursTemperature 180cC 22O"CBefore deodorization

Peroxide value 7.4 6.5Free Iuuy acids 0.17% 0.31%Color

R,d 5.0 1.7Yellow 50 17

After deodorizationPeroxide value 0.0 0.0Free fatty acids 0.14% 0.04%Color

Roo 0.3 1.7Yellow 30 17

tNFORM. Vol. 8. no. 11 (Noyembef 1997)

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