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STUDIES ON CRYOGENIC GRINDING OF CUMIN SEEDK.K. SINGH'

Central Institute ofAgricultural EngineeringNabibagh. Berasia RoadBhopal - 462 038 IndiaAND

T.K.GOSWAMIDepament ofAgricultural and Food EngineeringIndian Institute of TechnologyKharagpur - 721 302 India

Accepted for Publication February 8, 1999

ABSTRACTStudies on grinding of cumin seed at various cryogenic and ambienttemperatures were conducted to observe its influence on volatile oil content and

its components, panicle size distribution, volume mean diameter and specificenergy consumption. An increase in temperature in the cryogenic range (-160to -7OC) had no significant effect on volatile oil content, whereas increase intemperature in the ambient range (40 to 85C) significantly reduced the volatileoil contentfrom 2.86 to 2.26 mL/IOOg. The volatile oil components, a-pinene,P-pinene, y-tepinene, p-cymene and cuminaldehyde were not significantlyaffected by grinding temperature in the cryogenic temperature range. However,these components decreased significantly with increase in grinding temperatureunder ambient condition. With increase in temperaturefrom 160 to -7OC or 12number of rotor ribs, the volume mean diameter of cumin powder increasedquadratically from I29 to I64pm and the specific energy consumption increasedfrom 72 to 108 kJ/kg.

INTRODUCTIONCumin seed contains 2 to 4%volatile oil and 15% fat (Pruthi 1980). Thehigh fat content in cumin seed poses problems and is an important consideration

I Address to whom correspondence should be made:Dr.K .K . Singh. Scientist. Central Institute ofAgricultural Engineering, Nabibagh. Berasia Road, Bhopal - 462 038 IndiaJournal of Food Process Engineering 22 (1999) 175-190. AN Rights Resewed.@Copyright1999 by Food & Nutrition Press, Inc.. Trumbull, Connecticut. 175

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176 K.K. SINGH and T.K. GOSWAMI

in grinding. During grinding, the temperature of the product rises which varieswith the oil and moisture content of the spices (Pruthi and Misra 1963), butspices lose a significant fraction of their volatile oil or flavoring components dueto this temperature rise. The losses of volatile oil for different spices have beenreported to be about 37% for nutmeg, 14% for mace, 17 % for cinnamon and17% for oregano (Andres 1976). The volatile oil during grinding of carawayseed has been reported to be 32% less at the temperature of 45C than that at-17C (Wolf and Pahl 1990). During grinding of black pepper in a kitchengrinder, the application of liquid nitrogen resulted in 26% increase in volatileoil at the product temperature of 62C (Murthy ef al. 1996). The temperature riseof the product can be minimized to some extent by circulating cold air or wateraround the grinder. But this technique is not sufficient to significantly reduce thetemperature rise of the product.The loss of volatile oil can be significantly reduced by cryogenic grindingtechnique (Pruthi 1987). Liquid nitrogen at -195.6C provides the refrigerationneeded to precool the spices and maintain the desired low temperature byabsorbing the heat generated during the grinding operation. In addition tomaintaining the low temperature, vaporization of the liquid nitrogen to gaseousstate, in effect, creates an inert and dry atmosphere for additional protection ofspice quality. Precooling of the spice and continuous ow temperature maintainedwithin the mill reduce loss of volatile oils and moisture thereby retaining mostof the flavor strength per unit mass of spice.The extremely low temperature in the grinder embrittles the spices whichconsequently go through ductile-to-brittle ransition and can be fractured readily.At low temperature, the fat present in the spices also gets solidified andembrittled; they crumble easily permitting grinding to finer and more consistentsize. Thus considerably smaller particle size can be obtained under cryogenicconditions. The finely ground spices spread their flavor uniformly throughoutthe product body in which they are used, thereby reducing the problem of largespecks appearing in the food products. With cryogenic grinding, the temperatureof the products cau be as low as -195.6C. But such low temperatures are notrequired for all the spices. In practice, it is regulated anywhere from -195.Kto a few degrees below ambient temperatures (Russo 1976). The temperature tobe used isdetermined by parameters, viz., the final product size. color required,etc., of the product.The spraying of liquid carbon dioxide directly into the turbo mill wasstudied for grinding of pepper (Landwehr and Pahl 1986). It was reported thatalmost all experiments without chilling caused choking of sieve and ultimatelybreakdown of the mill.Watanabe (1978) reported that grinding of nutmeg was impossible above2OC. but it was easily ground at temperatures below -4OC. Thus it was shownthat the efficiency of grinding mainly depends on grinding temperatures. It was

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CRYOGENIC GRINDING OF CUMIN SEED 177

recommended that in order to prevent the ground powder from sticking to themachine, grinding should be done at low temperature when those oily and stickymaterials are ground. Particle size distribution depended mainly on the speed ofthe grinder's rotor. The higher speed of the rotor produced finer particles. Atthe same speed, the lower temperature resulted in finer particle size. There wasless loss of essential oil and moisture in cryo-ground nutmeg pow der than in theambiently ground powder.The studies on cryogenic grinding of Chinese herbal medicinal plantsrevealed that the product size was influenced by the rotary tip velocity and thesize of the screen (Li et al. 1991). It was also found that the color and otherproperties of the cryoground material were not changed and the flavor andnutrients of the medicines was not lost.

MATERIALS AND METHODSExperimental Set Up

A diagram of the cryogenic grinding system is shown in Fig. 1. It consistsof a precooler to lower down the temperature of spices below their brittle pointand freezing point of oil. The main com ponents of precooler is screw conveyorassembly which is made of 600 mm long and 50 mm diameter aluminum screw.The shaf t is enclosed in a 70 mm diameter and 655 mm long aluminum barrel.At the upper portion of the barrel, a distributor made of copper tube having 200mm length and 10mm internal diameter is fixed. The distributor has number ofperforations to spray liquid nitrogen over the material being conveyed throughthe barrel. There are three rows of perforations in a zig-zag manner, one atcenter and two at 45" angle from the center. The distributor is fixed at 10mmdistance from the inlet to allow thorough mixing of the liquid and vapor nitrogenwith the material, and to freeze the oil present in the material. An air compres-sor (Model HS-WP-1, igh Speed Appliances, M umbai, India) is used to supplycompressed air to the liquid nitrogen dewar. The resulting pressure helps theliquid to flow out of the dewar. The double walled, vacuum insulated dewar(IBP Co. Ltd., Mum bai, India) having capacity of 55 L is used for storage andtransfer of LN 2. An LN2 transfer assembly (IBP Co. Ltd., Mumbai, India) isfixed over the dewar to regulate the flow rate of the liquid nitrogen passing todistributor attached to conveyor assembly. A 370W, ingle phase variable speedD.C. motor was used to operate the conveyor. The shaft of the gear reductionunit was coupled with the screw shaft through a coupling made of Hylam(Bakelite Fabric Reinforced).A grinder (Model Pulverisette 14, Fritsch Industries, Germany) wasattached with the cryogenic grinding system. The main components of the

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CRYOGENIC GRIND ING OF CUMIN SEED 179

grinder were a 88.5 mm diameter rotor rotating at a peripheral velocities of 6 9m/s (15000 revolutions per minute) and 92 m/s (20000 revolutions per minute).The number of fixed ribs on the rotor could be set at 8 or 12, depending uponthe requirements. The rotor was surrounded by a sieve ring of trapezoidalopening of uniform size. Sieve rings of different opening sizes (0.08,O. 12 ,0 .2 ,0.5 and 1 O mm) were available. However, for the experimental purpose only0.5 and 1 O mm sieves were chosen. The sieve opening size controlled the finalproduct size. The operation of grinding was performed by impact and attrition.The impact was achieved by the material being struck with rotor ribs, whereasthe attrition was achieved while the seeds were present between the stationerysieve ring and the fast moving rotor. The speed of the rotor could be controlledthrough an in-built control mechanism.The ground powder was collected in the collector pan from an outlet. Anylon bag was attached to the outlet with a locking clamp. The nylon bagretained the particles and allowed the nitrogen vapor to escape from the grinder.The overall dimension of the grinder was 465 mm X 320 mm x 400 mm. Thegrinder was operated by a 800 W, single phase electric motor.Raw Material

Cumin seed was obtained from the local market during February-March,1995. The seed might be mixture of different varieties. The initial averagemoisture content of the seed was 9 .5 % d.b. and the fat content was 15%.Experimental Procedure

Fo r experimentation, the thermocouple bulb was placed in the collecting panin such a manner that it could measure the temperature of the ground productjust com ing out through the screen perforations. The com pressor was run beforestarting the experiments. The outlet valve of the com pressor was opened slightlyso as to get the required preset pressure in the liquid nitrogen (LNJ dewardepending upon the grinding temperature to be m aintained. Th e valve of transferline was opened to enable the liquid nitrogen flow into the distributor of thescrew conveyor assembly. The screw conveyor assembly and the grinder werecooled to the desired temperature of grinding (-160 to -7OC). The speed ofscrew conveyor was selected through a variable speed D.C. motor. The screwconveyor was run at a speed required for maintaining the desired level of feedrate to the grinder. Samples of 200 g material w ere filled into the inlet of thescrew conveyor assembly. The grinder was run at the selected speeds of 69 and92 m/s. The m aterial was allowed to enter into the grinder after passing throughthe precooler. The grinding took place at the predecided temperature in therange of -160 to -7OC at the interval of 30C with variation of f 3 C . In the caseof temperature rise during grinding, the flow rate of liquid nitrogen was

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180 K .K . SINGH and T.K. GOSWAMI

increased by increasing the opening of transfer line valve. During grinding, thepower consumed for grinding the material was measured by using the wattmeter(range 0-75OW) onnected to the motor. The powder was collected in a bagattached to the outlet of the chute and the nitrogen vapor let out.The powder samples were packed into moisture resistant flexible pouchesimmediately after grinding. They were sealed properly to check ingress ofmoisture from the surrounding atmosphere. The samples were stored at -1OC illthey were analyzed for particle size distribution and volatile oil content.Analytical Methods

Particle Size. The particle size analysis was carried out by laser scatteringusing the Malvern Particle Sizer (Malvern 3601,Malvern Instruments Ltd.,England).The selection of the carrier liquid is an important consideration in samplepreparation for determination of the particle size by Malvern Particle Sizer.Distilled water was used as a carrier liquid for this experiment. It fulfilled therequirement of being transparent to the desired wavelength as well as beingchemically neutral and had refractive index different from that of the sampleparticle. It contained a dispersant (electroactive), but did not dissolve theparticle. A blank reading was taken before measurement.Specific Energy Consumption.A 3-phase wattmeter (range 0-750 , eastcount 5 W) as connected with the grinder to measure the power consumed andultimately to measure the energy required in grinding. The grinder was runempty and no-load power was measured as 300 and 500W at 69 and 92 m /srespectively. Power under load was measured at each set of experiments. Thereading was recorded when the wattmeter indicator showed constant reading.The power at no-load was subtracted from the power at load condition tocalculate the actual power required in grinding operation. The following formulawas used to calculate the specific energy consumed in grinding.

Power consumed (W) x 3.6Feed rate (ka)pecific energy consumption, kJFg =

Volatile Oil. The volatile oil content of cumin powder ground undercryogenic aswell ambient conditions was estimated by distillation method usingClevenger apparatus (Pearson 1973).Gas Chromatography of Volatile Components. The volatile oil wasextracted from the cumin powder ground at different temperatures under

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CRYOGENIC GRINDING OF CUMIN SEED 181

cryogenic and ambient conditions. The oil was extracted by steam distillationmethod asdescribed earlier. The volatile components, viz., a-pinene, 8-pinene,y-terpinene, p-cymene and cuminaldehyde were determined using the followingprocedure. Each sample were measured three times and the standard deviationwas calculated.Analysis of volatile oil was performed using a gas chromatograph(Chrompack, model 9001) equipped with flame ionization detector (FID).Separation was achieved using a capillary column of 25 m length, 0 .32 mm I.D.and 0.30 pm film thickness WCOT Fused Silica, and stationery phase as FFAP-CB. A sample of one microliter was injected at the initial column temperatureof 50C, which was held for one minute to allow the sample to volatise. Thetemperature was then increased to 17OC at the rate of 10C/min and it was heldat 170C for one minute . The injector port temperature was maintained at 200C.The maximum oven temperature was kept constant at 200C and detectortemperature was maintained at 210C. Nitrogen was used as the carrier gas andits flow rate was maintained at 25 pLlmin.Identification of the individual components was made by comparing the peakretention times with those of authentic standards. Peak area of the componentswas measured using the MOSAIC software.

RESULTS AND DISCUSSIONParticle Size Distribution

Particle size distribution of cumin powder ground at different temperaturesin the range of -160 to -7OC using rotors with 12 ribs is shown in Fig . 2. As thegrinding temperature increased from -160 to -7OC. there was an increase in theparticle size for the same cumulative volume fraction. Similar particle sizedistributions of ground caraway powder at different grinding temperatures (0 to44C) were observed by Wolf and Pahl (1990).Volume Mean Diameter

Figure 3 represents the effect of grinding temperature on volume meandiameter of the particles with either 8 or 12 ribs in the rotor. The volume meandiameter increased with increasing grinding temperature from -160 to -7OC forboth the rotors and it followed a second order polynomial relationship.The rotor with 12 ribs produced finer particles in the range of 129 to 164pm, whereas the rotor with 8 ribs produced particles in the range of 153 to 215pm depending upon grinding temperature.

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182 K.K. SINGH and T.K. GOSWAMI

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110 100Particle size, pm m5 6 7-31000FIG. 2 . PARTICLE IZE DISTRIBUTION OF CUMIN POWDER GROUND AT DIFFERENT

TEMPERATURES FOR 12 ROTOR RIBS

Specific Energy ConsumptionFigure 4 represents the variation in specific energy consumption withgrinding temperature at 8 and 12 number of rotor ribs. It is observed that thespecific energy consumption increased with increasing grinding temperaturefrom -160 to -7OC for both the rotors and it followed a second order polynomialrelationship. It is obvious that at low grinding temperatures, the degree of

brittleness of the material increased due to which it required less energy ingrinding.The specific energy for grinding with 8 ribs was 55 to 98 kJ/kg. whereaswith 12 ribs, it was 72 to 108 kJ/kg depending upon the grinding temperature.

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CRYOGENIC GRINDING OF CUMIN SEED 183

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100 ' I 1 I- / S O - / 6 0 -;40 - 1 2 0 -100 -80 -Grinding temperature, O CFIG. 3. VARIATION IN VOLUME MEAN DIAMETER WITH GRINDING TEMPERATUREAT 8 AND 12 NUMBER OR ROTOR RIBS

Volatile OilThe volatile oil content as a function of grinding temperature is shown inTable 1. Increasing the grinding temperature from -160 o -7OC resulted in nosignificant change in volatile oil content. How ever, Landwehr and Pahl (1986)reported a decrease in volatile oil content of pepper with increasing grindingtemperature from -10 o 50C. he difference in the trend of results from thepresent study might be owing to the fact that volatile oil of pepper consisted ofcomponents having low boiling point which evaporated at correspondingtemperatures. Since cumin was ground at much lower temperatures than pepper,the loss of volatile oil was found to be nonsignificant.During ambient grinding, the volatile oil decreased from 2.86 to 2.26mL/lOO g with increasing grinding temperature from 40 to 85C (Table 1). Thestatistical analysis of the da ta (Table 2) evealed that the decrease in volatile oilwas significant at all the grinding temperatures (PS0.01) nder ambientcondition. In the ambient grinding process the mass transfer increased becauseof increase in vapor pressure at higher temperatures which resulted in a loss ofvolatile oil at corresponding temperatures (Wolf and Pahl 1990).

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FIG. 4. VARIATION IN SPECIFIC ENERGY CONSUMPTION WITH GRINDINGTEMPERATURE AT 8 AND 12 NUMBER OR ROTOR RIBS

TABLE 1 .AMOUNT OF VOLATILE OIL PRESENT IN CUMIN POWDERGROUND U NDER CRYOGENIC AND AMBIENT CONDITIONS,Gl l00 G OF POWDER ON DRY BASIS

Cryogenic Grinding, OC Ambient Grinding, "C-160 -130 -100 -70 40 55 65 I5 85

M m 3.30 3.28 3.28 3.26 2.86 2.13 2.55 2.36 2.26Standard 0.01 0.02 0.01 0.02 0.02 0.02 0.02 0.01 0.02deviation

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CRYOGENIC GRINDING OF CUMIN SEED I85

TABLE 2.ANALYSIS OF VARIANCE FOR VOLATILE OIL EXTRACTED FROM CRYOGENICALLYAND AMBIENTLY GROUND SAMPLE OF CUMIN POWDER

Source of Variation

:ryogenicalty groundReplicationSampleError

h b i e n t l y groundReplicationSampleError

Iegrees of Mean Fa, LSD:reedom Sauare

2 5 . 3 4 ~os 0.24Ns3 6.75 x 10' 3.0"6 2.25 x 10.'

2 2.7 8 X10.' 1 .JNS4 1.86 x10' 871' 0 . 038 2.13

* Significant (PsO.01)NS Non-Significant (Pr0.05)

About 3 1% more retention of volatile oil was observed in the case ofcryogenic grinding than in ambient grinding. These results support publishedliterature of Wistreich and Schafer (1962); Perkins and Soskel (1976); Andres(1976) and Murthy et al. (1996), who reported an increase in volatile oilretention in the order of 30, 14-36. 14-37% and 36% respectively in the caseof cryogen ic grinding of spices, such as, nutmeg, mace, cinnam on, oregano andblack pepper. However, Pesek ef al. (1985) observed no difference in thevolatile oil content between cryogenic and ambient grinding of cumin seed, butthe authors have not mentioned the temperatures in cryogenic and ambientgrinding.Analysis of Flavoring Components

Figure 5 shows the chromatogram of volatile oil of cumin powder groundat -1OOC. In the Figure, 25 peaks are shown, whereas Varo and Heinz (1970)reported 33 peaks for volatile components of cum in. The componen ts present inthe form of traces (less than 0.1%) have not been shown in the chromatogram.Figure 6 shows the chrom atogram of volatile components of cumin powderground at the temperature of 85C. At this grinding temperature, only 19 peakscould be obtained. It seems that either some of the h ighly volatile componentshaving low boiling point might have been completely lost o r these m ight havebeen present in the form of traces, which have not been show n in the chromato-gram. Similar chromatograms at other temperatures under study were alsoobtained.

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186 K .K . SINGH and T.K. GOSWAMI

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-_i L A. .Retention time ,minFIG. 5. CHROMATOGRAM OF VOLATILE OIL COMPONENTS OF CUMIN POWDERGROUND CRYOGENICALLY AT -1OOCTable 3 represents the values of volatile components in integration unit

ground in the temperature range of -160 to - 7 K , whereas Table 4 represents thevalues of volatile components ground under ambient condition in the range of55 to 85C. The analysis of variance of the data (Table 5 ) revealed that theamounts of volatile components are not significantly differen t at all the grindingtemperatures (P 0.01) under cryogenic condition.

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CRYOGENIC GRINDING OF CUMIN SEED 187

In the ambient condition, the amount of volatile components decreased withincreasing grinding temperature from 55 to 85C (Table 4). The analysis ofvariance (Table 5 ) indicated that the decrease of all the volatile components ateach level of grinding temperature was significant (P 0.01) under ambientcondition.

f - t e r p i n e n e

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I

FIG. 6. CHROMATOGRAM OF VOLATILE OIL COMPONENTS OF CUMIN POWDERGROUND AMBIENTLY AT 85C

The increase in retention of various volatile components viz. a-pinene, 0-pinene, y-terpinene, p-cymene and cuminaldehyde were in the order of 22%.20.2%, 7.4%, 40.9% and 35% respectively under cryogenic conditioncomparedwith those obtained under ambient condition.

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188 K.K. SINGH and T.K. GOSWAMI

TABLE 3.VOLATILE COMPONENTS OF CUMIN GROUND UNDER CRYOGENIC CONDITIONS(VALUES ARE IN THE INTEGRATION UNITS. x 1V)

Components Temperatures. "C-160 -130 -100 -70

a- pinene 0.457 0.455 0.451 0.452(f .001) (f .001) (f .002) (f .002)

8- pinene 5.0 5 O 4.99 4.98(f .02) (f .01) (f .01) (f .01)

y- erpinene 7.75 7.75 7.73 7.74(f .01) (f .01) (f .02) (f .01)

(f .01) ( * 0.01) (f .02) (f .01)p- cymene 13.44 13.43 13.40 13.40

Cuminaldehyde 15.53 15.51 15.517 15.49(f 0.01) (f .01) (f .01) (f .01)

Values in parentheses are the standard deviation of three replicates

TABLE 4.VOLATILE COMPONENTS OF CUMIN POWDER GRO UND AMBIENTLY (VALUES AREIN TH E INTEGRATION UNITS, X lo6)

Components Temperatures. OC55 65 75 85

a- inene 0.396 0.378 0.369 0.352(f .002) (f .001) (* 0.001) (f .001)

8-pinene 4.53 4.29 4.18 3.98(f .02) (f .03) (f .03) (f .01)

y-terpinene 7.36 7.28 7.16 6.99(* 0.01) (f .02) (f0.01) (f .01)

pcymene 11.2 10.4 9.63 7.92(f .04) (f .06) (f .02) (f .02)

Cuminaldehyde 13.57 12.05 11.36 10.088(f .02) (f .02) (f .02) (f .01)Values in parentheses are the standard deviation of three replicates

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CRYOGENIC GRINDING OF CUMIN SEED 189

TABLE 5.ANALYSIS OF VARIANCE FOR CO MPON ENTS O F CUM IN POWDER GROU NDCRYOGENICALLY AND AMBIENTLYSource of Cryogenic Grinding Ambient GrindingVariation D.F . M.S.S Fa, M.S.S. Fa, LSD(YL pinene 3 1.9x1O5 4.25 1o x 10-3 2.97 x 10'* 0.004Replication 2 3.7x1O4 0.83 1.2 ~1 0- 7 3. 52 ~1 0'Error 6 4 . 5 ~ 1 0 . ~ 3.4X1O6b- pinene 3 1 . 2 ~ 1 0 3 3.20 1.5x 10' 1.47X lo'* 0.098Replication 2 2. 3~ 10 .' 0.60 3.8x10-' 3 . 6 0 ~ 1 0 'Error 6 3.8X10.4 1. 1~ 10 -3y- terpinene 3 2.7~10' 1.36 7.5~10' 3.32x101* 0.046Replication 2 0 0 3.7~10' 1.61Error 6 2.OXlO.' 2.3 X 10'p ymene 3 9.7X104 4.0 5.87 4.53X lo2* 0.334Replication 2 2 . 4 ~ 1 0 . ~ 1.0 3.23x lo-* 2.49Error 6 2.4X10-4 1.29X 10.'

Cuminaldehyde 3 7 . 1 ~ 1 0 ' 4.0 6.31 1.05 X lo** 0.074Replication 2 1 .2~10-4 0.7 2 .4 4 ~1 0. ~ 0.40Error 6 1 . 8 ~ 1 0 ' 6.04x 10.'* Significant (Pk'O.01)

REFERENCESANDRES, C. 1976. Grinding spices at cryogenic temperatures retains volatilesand oils. Food Process. 37 (9). 52-53.LANDWEHR, D. and PAHL, M.H. 1986. Cold grinding of spices. Intl. J .Food Technol. Food Proc. Eng. 37, 174-185.LI, S., GE, S.,HUANG, Z., WANG, Q., HAO, H. and PAN, H. 1991.Cryogenic grinding technology for traditional Chinese herbal medicine.Cryogenics 31, 136-137.MURTHY, C.T., KRISHNAMURTHY, N.. RAMESH T. and SRINIVASARAO, P.N. 1996. Effect of grinding methods on the retention of blackpepper volatiles. J . Food Sci. Technol. 33 (4), 299-301.PEARSON, D. 1973. Laboratory Techniques for Food Analysis, LondonButterworths.

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PERKINS, W.E. and SOSKEL, F.F. 1976. Cryogenic grinding in the foodindustry. Presented in the 36th Annual Meeting of the Institute of FoodTechnologists, June 6-9, Anaheim, CA.PESEK, C.A., WILSON, L.A. and HAMMOND. E.G. 1985. Spice quality:effect of cryogenic and ambient grinding on volatiles. J. Food Sci. 50 (3),

PRUTHI, J.S. 1980. Spices and Condiments - Chemistry, Microbiology andTechnology. Academic Press, Inc., New York.PRUTHI, J.S. 1987. Cryomilling - he latest technology of cold grinding ofspices and condiments. In Technical Compendium. National Symposium onSpice Industries. April. 38-47, AFST, Delhi Chapter, India.PRUTHI, J.S. nd MISRA, B.D. 1963. Spice Bull, India, 3 ( 3 - 3 , 8. As citedby Pruthi 1987.RUSSO, J.R. 1976. Advanced techniques in new spice plant - ryogenicgrinding. Carousel material handling. Food Engineering Intl. I (8),33-35.VARO, P.T. and HEINZ, D.E. 1970. Volatile components of cumin seed oil.J. Agric. Food Chem. 18 (2), 234-238.WATANABE er al. 1978. Cryomilling of nutmeg. Nippon Shokuhin KogyoGakkaijah, 25 (8), 275-280. As cited by Pruthi 1987.WISTREICH, H.E. and SCHA FER, W.F. 1962. Freeze grinding ups productsquality. Food Eng. 34 ( 3 , 62.WOLF, T. and PAHL, M.H. 990. Cold grinding of caraway seeds in impactmill. Intl. J . Food Technol. Food Proc. Eng. 41 (10). 596-604.

599-601.