S198 JOURNAL OF FOOD SCIENCE—Vol. 71, Nr. 3, 2006Published on Web 3/15/2006

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S: Sensory & Nutritive Qualities of Food

Radiation Processing of Minimally ProcessedCarrot (Daucus carota) and Cucumber(Cucumis sativus) to Ensure Safety: Effecton Nutritional and Sensory QualitySSSSSAAAAACHINCHINCHINCHINCHIN N. H N. H N. H N. H N. HAJAREAJAREAJAREAJAREAJARE, , , , , VVVVVARSHAARSHAARSHAARSHAARSHA S. D S. D S. D S. D S. DHOKANEHOKANEHOKANEHOKANEHOKANE, R. S, R. S, R. S, R. S, R. SHASHIDHARHASHIDHARHASHIDHARHASHIDHARHASHIDHAR, A, A, A, A, ARRRRRUNUNUNUNUN S S S S SHARMAHARMAHARMAHARMAHARMA, , , , , ANDANDANDANDAND J J J J JAAAAAYYYYYANTANTANTANTANT R. B R. B R. B R. B R. BANDEKARANDEKARANDEKARANDEKARANDEKAR

ABSTRAABSTRAABSTRAABSTRAABSTRACTCTCTCTCT: I: I: I: I: In the prn the prn the prn the prn the present studyesent studyesent studyesent studyesent study, r, r, r, r, radiation pradiation pradiation pradiation pradiation processing of minimally processing of minimally processing of minimally processing of minimally processing of minimally processed carrocessed carrocessed carrocessed carrocessed carrot and cucumber at a dose of 2 kGot and cucumber at a dose of 2 kGot and cucumber at a dose of 2 kGot and cucumber at a dose of 2 kGot and cucumber at a dose of 2 kGyyyyywas carried out. The effect of this treatment on different quality parameters such as vitamin C content, total caro-was carried out. The effect of this treatment on different quality parameters such as vitamin C content, total caro-was carried out. The effect of this treatment on different quality parameters such as vitamin C content, total caro-was carried out. The effect of this treatment on different quality parameters such as vitamin C content, total caro-was carried out. The effect of this treatment on different quality parameters such as vitamin C content, total caro-tenoids content, sensortenoids content, sensortenoids content, sensortenoids content, sensortenoids content, sensory qualityy qualityy qualityy qualityy quality, textur, textur, textur, textur, textureeeee, and color was deter, and color was deter, and color was deter, and color was deter, and color was determined omined omined omined omined ovvvvver a storer a storer a storer a storer a storage perage perage perage perage period of 16 d at 8 °C to 10 ° C. Iiod of 16 d at 8 °C to 10 ° C. Iiod of 16 d at 8 °C to 10 ° C. Iiod of 16 d at 8 °C to 10 ° C. Iiod of 16 d at 8 °C to 10 ° C. In then then then then thecase of cucumbercase of cucumbercase of cucumbercase of cucumbercase of cucumber, tr, tr, tr, tr, treatment of irreatment of irreatment of irreatment of irreatment of irradiation as wadiation as wadiation as wadiation as wadiation as well as storell as storell as storell as storell as storage perage perage perage perage period shoiod shoiod shoiod shoiod showwwwwed no significant change in the total vitamined no significant change in the total vitamined no significant change in the total vitamined no significant change in the total vitamined no significant change in the total vitaminC content of either the control or the irradiated samples. In the case of carrots, a 2-kGy dose had no significant effectC content of either the control or the irradiated samples. In the case of carrots, a 2-kGy dose had no significant effectC content of either the control or the irradiated samples. In the case of carrots, a 2-kGy dose had no significant effectC content of either the control or the irradiated samples. In the case of carrots, a 2-kGy dose had no significant effectC content of either the control or the irradiated samples. In the case of carrots, a 2-kGy dose had no significant effect(((((PPPPP < 0.05) on total vitamin C content of the samples < 0.05) on total vitamin C content of the samples < 0.05) on total vitamin C content of the samples < 0.05) on total vitamin C content of the samples < 0.05) on total vitamin C content of the samples. H. H. H. H. Hooooowwwwwevevevevevererererer, dur, dur, dur, dur, during storing storing storing storing storageageageageage, both contr, both contr, both contr, both contr, both control as wol as wol as wol as wol as well as irrell as irrell as irrell as irrell as irradiatedadiatedadiatedadiatedadiatedsamples shosamples shosamples shosamples shosamples showwwwwed significant decred significant decred significant decred significant decred significant decrease (ease (ease (ease (ease (PPPPP < 0.05) in vitamin C content. < 0.05) in vitamin C content. < 0.05) in vitamin C content. < 0.05) in vitamin C content. < 0.05) in vitamin C content. TTTTTotal carotal carotal carotal carotal carotenoids content in carrotenoids content in carrotenoids content in carrotenoids content in carrotenoids content in carrot rot rot rot rot remainedemainedemainedemainedemainedalmost unchanged after irradiation as well as during storage. Sensory evaluation results showed that irradiation hadalmost unchanged after irradiation as well as during storage. Sensory evaluation results showed that irradiation hadalmost unchanged after irradiation as well as during storage. Sensory evaluation results showed that irradiation hadalmost unchanged after irradiation as well as during storage. Sensory evaluation results showed that irradiation hadalmost unchanged after irradiation as well as during storage. Sensory evaluation results showed that irradiation hadno significant (no significant (no significant (no significant (no significant (PPPPP < 0.05) effect on the ratings of any of the sensory attributes in carrot. Radiation processing of < 0.05) effect on the ratings of any of the sensory attributes in carrot. Radiation processing of < 0.05) effect on the ratings of any of the sensory attributes in carrot. Radiation processing of < 0.05) effect on the ratings of any of the sensory attributes in carrot. Radiation processing of < 0.05) effect on the ratings of any of the sensory attributes in carrot. Radiation processing ofcucumber affected the flavcucumber affected the flavcucumber affected the flavcucumber affected the flavcucumber affected the flavor significantlyor significantlyor significantlyor significantlyor significantly. H. H. H. H. Hooooowwwwwevevevevevererererer, this change did not alter the o, this change did not alter the o, this change did not alter the o, this change did not alter the o, this change did not alter the ovvvvverererererall acceptability of cucumberall acceptability of cucumberall acceptability of cucumberall acceptability of cucumberall acceptability of cucumber.....TTTTTexturexturexturexturextural studies ral studies ral studies ral studies ral studies revevevevevealed that in both carrealed that in both carrealed that in both carrealed that in both carrealed that in both carrot and cucumberot and cucumberot and cucumberot and cucumberot and cucumber, ther, ther, ther, ther, there was no significant change (e was no significant change (e was no significant change (e was no significant change (e was no significant change (PPPPP < 0.05) in fir < 0.05) in fir < 0.05) in fir < 0.05) in fir < 0.05) in firmness ofmness ofmness ofmness ofmness ofthe central region after irradiation, whereas the peripheral region in carrot showed significant reduction in firmness.the central region after irradiation, whereas the peripheral region in carrot showed significant reduction in firmness.the central region after irradiation, whereas the peripheral region in carrot showed significant reduction in firmness.the central region after irradiation, whereas the peripheral region in carrot showed significant reduction in firmness.the central region after irradiation, whereas the peripheral region in carrot showed significant reduction in firmness.IIIIIn the case of cucumbern the case of cucumbern the case of cucumbern the case of cucumbern the case of cucumber, ther, ther, ther, ther, there was no significant change (e was no significant change (e was no significant change (e was no significant change (e was no significant change (PPPPP < 0.05) in the textur < 0.05) in the textur < 0.05) in the textur < 0.05) in the textur < 0.05) in the texture of both pere of both pere of both pere of both pere of both peripheripheripheripheripheral ral ral ral ral regionsegionsegionsegionsegions. H. H. H. H. Hooooowwwwwevevevevevererererer,,,,,during storage, the peripheral regions of carrot and cucumber showed significant increase in firmness. Color mea-during storage, the peripheral regions of carrot and cucumber showed significant increase in firmness. Color mea-during storage, the peripheral regions of carrot and cucumber showed significant increase in firmness. Color mea-during storage, the peripheral regions of carrot and cucumber showed significant increase in firmness. Color mea-during storage, the peripheral regions of carrot and cucumber showed significant increase in firmness. Color mea-surement results indicated no drastic change in color coordinates of carrot samples. Thus, the nutritional as well assurement results indicated no drastic change in color coordinates of carrot samples. Thus, the nutritional as well assurement results indicated no drastic change in color coordinates of carrot samples. Thus, the nutritional as well assurement results indicated no drastic change in color coordinates of carrot samples. Thus, the nutritional as well assurement results indicated no drastic change in color coordinates of carrot samples. Thus, the nutritional as well assensory quality of minimally processed foods did not alter significantly after gamma irradiation.sensory quality of minimally processed foods did not alter significantly after gamma irradiation.sensory quality of minimally processed foods did not alter significantly after gamma irradiation.sensory quality of minimally processed foods did not alter significantly after gamma irradiation.sensory quality of minimally processed foods did not alter significantly after gamma irradiation.

KKKKKeyworeyworeyworeyworeywords: gamma irrds: gamma irrds: gamma irrds: gamma irrds: gamma irradiation, minimally pradiation, minimally pradiation, minimally pradiation, minimally pradiation, minimally processed foodsocessed foodsocessed foodsocessed foodsocessed foods, carr, carr, carr, carr, carrot, cucumberot, cucumberot, cucumberot, cucumberot, cucumber, vitamin C, total car, vitamin C, total car, vitamin C, total car, vitamin C, total car, vitamin C, total carotenoidsotenoidsotenoidsotenoidsotenoids, textur, textur, textur, textur, textureeeee

Introduction

In India as well as in many parts of the world there is an increasein consumption of raw fresh produce such as vegetables, fruits,

and sprouts. These products of plant origin are mostly consumed fortheir fiber, vitamins, and mineral content (Gopalan and others2004). Drastic treatments such as heating and cooking may lead toloss of vitamins and hence, these products are either minimally pro-cessed or eaten raw. Fruits and vegetables carry a natural non-patho-genic epiphytic microflora. However, during growth, harvest, trans-portation, further processing, and handling, the produce can becontaminated with pathogens from human or animal sources (SCF2002). Also, cutting, slicing, skinning, and shredding removes ordamages the protective surfaces of the plant or fruit, which facilitateentry of pathogenic bacteria into these products. Surveillance of veg-etables has indicated contamination of these commodities with var-ious bacterial pathogens, including Salmonella, Shigella, Escherichiacoli O157:H7, Listeria monocytogenes, and Campylobacter. This has ledto a number of outbreaks of foodborne diseases in many countries(Olsen and others 2000). The carrot and cucumber samples from aMumbai market were found to be poor in microbiological quality; 72%of the carrot samples were contaminated with fecal coliforms, and12% were positive for L. monocytogenes (Bandekar and others 2005).

Radiation processing as a method of food processing and pres-

ervation is being used on a large scale and is known to inactivatemicroorganisms present in food commodities (Diehl 1990; Diehland Josephson 1994; ICGFI 1999; Mishra and others 2004). Unlikethermal processing, which has deteriorating effects on vitamins,flavoring compounds, and textural properties of foods (Wilkinsonand Gould 1998), irradiation is a cold process. Although irradiationis known to destroy vitamins in pure systems, in food commoditiesthe destruction may not be significant due the mutually protectiveaction of various food constituents on each other (Diehl 1990).

Carrot and cucumber form important constituents of Indiansalads. These are generally peeled and sliced and are used for saladdressings or shred or cut into very small pieces to mix with otheringredients of salads. Other uses of these salad components in-clude halwa preparations, pickles, and parathas.

The present study was carried out to evaluate quality of radia-tion processed precut carrot and cucumber samples. Inoculatedpack studies done earlier with Salmonella Typhimurium and L.monocytogenes (Dhokane and others 2006) showed that a dose of2 kGy was sufficient to eliminate 5 log colony-forming units (CFU)/gof these bacterial pathogens. The effect of radiation processing onnutritional, textural, color, and sensory quality of these productsduring post-irradiation storage has been examined.

Materials and Methods

ChemicalsChemicalsChemicalsChemicalsChemicalsAll chemicals used were of analytical grade and were procured

JFS S: Sensory and Nutritive Qualities of Food

MS 20050662 Submitted 11/6/05, Revised 12/5/05, Accepted 12/31/05. Theauthors are with Food Technology Div., Bhabha Atomic Research Centre,Mumbai 400 085, India. Direct inquiries to author Bandekar (E-mail:jrb@magnum.barc.ernet.in).

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Radiation hygienized carrot and cucumber . . .

from SISCO Research Laboratories (Mumbai, India) unless other-wise specified.

Sample preparationSample preparationSample preparationSample preparationSample preparationTwelve different samples of carrot and cucumber were pur-

chased from various locations of Mumbai (local market). Thesesamples were washed in running tap water, were dried in air, andwere cut transversely into circular slices of about 1-cm thickness.About 50 g of each sample was packed in low-density polyethylene(LDPE) bags (35 �m gauge) measuring 15 cm × 15 cm. All the sam-ples were divided into 2 groups: control and irradiated.

Gamma irradiationGamma irradiationGamma irradiationGamma irradiationGamma irradiationGamma irradiation was carried out in a cobalt-60 Food Package

Irradiator (AECL, Ottawa, Canada) at Food Technology Div., Bhab-ha Atomic Research Centre, at a dose rate of 40 Gy/min. The doserate was determined using a standard Fricke dosimetry (Sehsted1970). Samples were irradiated at a dose of 2 kGy at 0 °C to 4 °C.After irradiation, the samples were stored at 8 °C to 10 °C. Becauseof climatic conditions in Mumbai, India, the temperature of chillcabinets in the local markets remain in the range of 8 °C to 10 °C.Hence, this temperature was selected for storage of the samples.

Vitamin C extraction and analysisVitamin C extraction and analysisVitamin C extraction and analysisVitamin C extraction and analysisVitamin C extraction and analysisVitamin C extraction and analysis was done in 3 different sets in

triplicate for both carrot and cucumber. The total vitamin C contentof both the samples was estimated according to standard AOACofficial microfluorometric method (AOAC 1990). Ten grams of sam-ple was ground in 50 mL of metaphosphoric acid–acetic acid solu-tion. All the ascorbic acid present in the homogenate was convertedto de-hydro ascorbic acid by activated charcoal. This total ascorbicacid was further reacted with o-phenylenediamine (Sigma Chem-ical Corp., St. Louis, Mo., U.S.A.) to form fluorescence conjugate.Total conjugate formed was measured by CS-5000 fluorimeter (Shi-madzu Corp., Kyoto, Japan). The excitation and emission wave-lengths were 350 nm and 430 nm, respectively. Concentration oftotal ascorbic acid in the samples was determined by comparingthe fluorescence of conjugate formed by standard ascorbic acid(AOAC 1990).

TTTTTotal carotal carotal carotal carotal carotenoids extrotenoids extrotenoids extrotenoids extrotenoids extraction and analysisaction and analysisaction and analysisaction and analysisaction and analysisTotal carotenoids extraction and analysis of carrot samples was

done in 3 different sets in triplicate. Total carotenoids analysis oncucumber was not carried out. Extraction and estimation of totalcarotenoids content of the carrot samples was done according tostandard AOAC official method (AOAC 1990) after slight modifica-tion. Ten grams of sample was finely ground in acetone: hexane(4:6) containing 0.05% butylated hydroxy toluene (BHT) as an an-tioxidant. It was then filtered through a sintered glass funnel. Theresidue was washed with 25 mL portions of acetone and then with25 mL hexane until the residue turned almost colorless. All wash-ings were pooled, and then acetone was removed from extract by5 100-mL washings of distilled water in the separating funnel. Up-per hexane layer was removed and passed over anhydrous sodiumsulfate to remove any traces of water. The volume of this hexanelayer was measured and absorbance was taken at a 452-nm wave-length. A calibration curve was plotted using standard �-carotenes(Sigma Chemical Corp.) with different concentrations rangingfrom 0.5 to 3.0 �g/mL in hexane. Absorbance of these samples wasmeasured at 452 nm, and a curve was plotted using standard con-centrations versus absorbance value. Concentration of total caro-tenoids was determined in terms of �-carotenes using slope valuecalculated from the standard curve.

Sensory evaluationSensory evaluationSensory evaluationSensory evaluationSensory evaluationSensory analysis of carrot and cucumber samples was carried out

for irradiated and non-irradiated samples after 24 h of storage at 8 °Cto 10 °C. Sensory evaluation was done by an expert panel of 18 re-searchers/scientists from different sections of Food Technology Div.,BARC, in a taste panel laboratory in individual partitioned compart-ments of a controlled environment room (Mishra and others 2004).The sensory panel consisted of 10 men and 8 women (aged 25 to50 y). The members were trained to recognize and score differentquality attributes including appearance, color, texture, odor, taste,and overall acceptability of minimally processed carrot and cucumberbefore actual testing. Standard triangular test (extended) was usedfor this assessment, and the results obtained were analyzed usingstatistical tools such as mean and standard deviation. A 7-point he-donic scale was used for marking, ranging from very poor to excellent.Sensory analysis for each commodity was done in 3 separate exper-iments to eliminate bias emerging from biological variation in sam-ples procured from various locations.

TTTTTexturexturexturexturexture analysise analysise analysise analysise analysisTexture analysis of carrot and cucumber samples was measured

using Instron, Universal Testing Instruments (TM Model, InstronEngineering Corp., Norwood, Mass., U.S.A.), which was equippedwith a 2-mm brass needle probe for penetration and a 100-kg loadcell. In sliced salads, the firmness of the tissue varies significantlyfrom center to the periphery and hence, texture was measured at 2positions in carrots—central and peripheral. In cucumber, howev-er, 2 peripheral positions were selected in addition to the centralone, due to the structural variation. The 1st peripheral position wasjust below placenta whereas the 2nd position was in between 2 pla-centas. Texture was calculated as maximum force (kg) measuringresistance to the penetration (5-mm fixed depth) imposed by thesample to the metal probe (Bourne and others 1966). The crosshead and chart speed was fixed to 2 cm/min and 10 cm/min, re-spectively. The instrument was calibrated before each use. Textureof the irradiated and non-irradiated (control) salad pieces was de-termined after every 4th day of storage until 16 d.

Color measurementColor measurementColor measurementColor measurementColor measurementColor measurement is a nondestructive test; hence, the same

sample can be repetitively used for analysis during the storage. Thus,color analysis of carrot samples was performed in 2 different sets. In1 set, the same sample was used for measurement of color during thestorage period. In another set, different packets were prepared andevery 4th day, 1 packet was used for analysis. After the analysis, sam-ples were discarded. The color of the carrot samples was measuredby reflectance using Minolta CM-3600d Spectrophotometer (KonicaMinolta Sensing, Inc, Osaka, Japan) through direct reading on thecentral region (Guevara and others 1996). The whole visible spec-trum (360 to 780 nm) was recorded (�� = 10 nm). Illuminant D65 and10° Observer were considered as references. The CIELAB parame-ters, that is, L* (lightness), a* (red component), b* (yellow compo-nent), C*ab (chroma) and h*ab (hue angle) were determined by usingJAYPAK 4808 software (Quality Control System, Version 1.2).

Statistical analysisStatistical analysisStatistical analysisStatistical analysisStatistical analysisThe data were analyzed using the Origin 6.1 software version

v6.1052 (B232) (OriginLab Corp., Northhampton, Mass., U.S.A.).For all the results, mean and standard deviations were calculated.The paired t-test was used to detect significant differences be-tween control and irradiated (2 kGy) samples for all the parameters,that is, vitamin C content, total carotenoids, sensory evaluationcolor, and texture, whereas 1-way analysis of variance (ANOVA) was

S: Sensory & Nutritive Qualities of Food

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Radiation hygienized carrot and cucumber . . .

used to detect significant differences within the same sample dur-ing the storage.

Results and Discussion

TTTTTotal vitamin C contentotal vitamin C contentotal vitamin C contentotal vitamin C contentotal vitamin C contentFigure 1 shows total vitamin C content of cucumber and carrot

over a storage period of 16 d. The vitamin C content of the controlcucumber ranged from 7.5 to 10.7 mg%, whereas that of irradiated(2 kGy) samples ranged from 6.5 to 9.0 mg% during storage. It wasfound that both the treatment of irradiation as well as the storageperiod had no significant effect (P < 0.05) in the total vitamin C con-tent of control as well as irradiated cucumber samples. In the caseof carrot, the total vitamin C content of the control samples rangedfrom 4.2 to 7.2 mg%, whereas that of irradiated samples rangedfrom 3.4 to 7.6 mg%. These values are similar to the values observedby Song and others (2006) in carrot juice. It was found that a 2-kGydose had no significant effect (P < 0.05) on total vitamin C contentof the carrot samples. However, during storage, both the control aswell as the irradiated samples showed significant decrease(P < 0.05) in vitamin C content. Song and others (2006) observedsimilar decrease in total vitamin C during storage. Large variationin vitamin C content in the control as well as the irradiated samples(carrot and cucumber) in terms of standard deviation can be attrib-uted to the biological variation among the samples because theywere procured from different locations at different times.

TTTTTotal carotal carotal carotal carotal carotenoids contentotenoids contentotenoids contentotenoids contentotenoids contentTotal carotenoids analysis was not done on cucumber. Figure 2

depicts total carotenoids content of control and irradiated carrotsamples. Total carotenoids in control samples ranged from 13.5 to15 mg%, whereas in irradiated samples it ranged from 12.5 to13.8 g%. Thus, the profile of total carotenoids in carrot was verymuch stable to irradiation and showed no significant change(P < 0.05) after irradiation when analyzed by paired t-test. The stor-age period also did not significantly alter the total carotenoids con-

tent in both the control and the irradiated samples. These resultsare in concurrence with the previous reports that radiation process-ing of carrot at a 2-kGy dose does not result in decrease in total car-otenoids content, including different isomeric forms of �-carotene(Sebastião and others 2002).

Sensory evaluation of carrot and cucumberSensory evaluation of carrot and cucumberSensory evaluation of carrot and cucumberSensory evaluation of carrot and cucumberSensory evaluation of carrot and cucumberSensory evaluation of both control and irradiated salad samples

was done after 24 h of storage at 8 °C to 10° C. The standard trian-gular test (extended) was used for this analysis to normalize thebias emerging from biological variation within the sample. It wasobserved that the panelists could not differentiate between un-treated and radiation processed samples of both carrot and cucum-ber (data not shown). Figure 3 depicts the sensory evaluation ofcontrol and irradiated carrot. There was no significant difference(P < 0.05) in appearance, color, texture, and odor of the irradiatedsamples compared with the control. In fact, there was a slight en-hancement in the taste (in terms of sweetness) of irradiated sam-ples, and the panel members liked these samples over the controls.This increase in the sweetness can be attributed to the breakdownof starch into monomer glucose units. In cucumber, however, tastepanelists could make out significant change (P < 0.05) in the textureof irradiated samples, which was evident from the ranking valuesfor this parameter (Figure 4). Nevertheless, this change was wellwithin acceptable limits and did not affect the overall acceptabil-ity of these samples. Other sensory parameters including appear-ance, color, odor, and taste showed insignificant change (P < 0.05)due to irradiation. These observations are in accordance with Khat-tak and others (2005).

TTTTTexturexturexturexturexture analysise analysise analysise analysise analysisTexture analysis was done at 1 central and 1 peripheral region of

carrot, whereas in cucumber, analysis was done at 2 peripheral re-gions and 1 central region. Figure 5 shows the texture profile of thecentral and peripheral region of the control and irradiated carrot.The texture of the central region of both the control and irradiatedsamples varied within a narrow range, and the force values were in

Figure 2—Total carotenoids content profile of control andirradiated (2 kGy) carrot samples during the storage. Totalcarotenoids were extracted and estimated from 10 g ofeach control and irradiated carrot samples on the day ofirradiation and every 4th d of storage until 16 d. All datapoints are the average of 3 experiments in triplicates. Thebar represents standard deviation.

Figure 1—Total vitamin C content profile of control and ir-radiated (2 kGy) carrot and cucumber samples during stor-age. Total vitamin C was estimated from 10 g of each con-trol and irradiated carrot and cucumber samples on the dayof irradiation and every 4th d of storage until 16 d. The graphindicates the vitamin C profile of control (—�—) and irradi-ated (2 kGy) (—�—) cucumber samples, control (—�—) andirradiated (2 kGy) (—�—) carrot samples. All data points arethe average of 3 experiments in triplicates. The bar repre-sents standard deviation.

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the range of 7.25 to 8.0 kg. Thus, no significant change (P < 0.05) infirmness was observed after irradiation. The storage period also hadno effect (P < 0.05) on the firmness of the central region of both thecontrol and irradiated carrot samples. Irradiation has been associat-ed with softening of plant tissues, specifically degradation of poly-

mers such as pectin and cellulose, which give hardness to the planttissues (Glegg and Kertesz 1956, 1957; McArdle and Nehemias 1956;Glegg 1957; Kertesz and others 1964; Somogyi and Romani 1964;Mishra and others 2004). In the peripheral region, the texture force

Figure 5—Texture analysis of central and peripheral regionof control and irradiated (2 kGy) carrot samples. Textureanalyses of both the carrot samples were done at centraland peripheral regions on the day of irradiation and every4th d of storage, until 16 d, using Instron Universal TestingInstrument. The graph indicates texture profile of centralregion of control (—�—) and irradiated (2 kGy) (—�—) carrotsamples, peripheral region of control (—�—) and irradiated(2 kGy) (—�—) carrot samples. Ordinate indicates force inkg measuring resistance to the penetration imposed by thesample to the probe. Abscissa indicates day of storage. Alldata points are the average of 3 experiments in triplicates.The bar represents standard deviation. Different letters acrossthe line (a to e) indicate the force values are significantlydifferent over a storage period at 0.05 level of significanceas tested by 1-way analysis of variance (ANOVA).

Figure 6—Texture analysis of central and peripheral regionI of control and irradiated (2 kGy) cucumber samples. Thetexture analysis of control and irradiated cucumber sampleswas done at the central and peripheral region I on the dayof irradiation and every 4th d of storage until 16 d, usingInstron Universal Testing Instrument. The graph indicatestexture profile of peripheral region I of control (—�—) andirradiated (2 kGy) (—�—) cucumber samples, central regionof control (—�—) and irradiated (2 kGy) (—�—) cucumbersamples. Ordinate indicates force in kg measuring resis-tance to the penetration imposed by the sample to the probe.Abscissa indicates day of storage. All data points are theaverage of 3 experiments in triplicates. The bar representsstandard deviation. Different letters across the line (a to e)indicate that the force values are significantly different overa storage period at 0.05 level of significance as tested by1-way analysis of variance (ANOVA).

Figure 3—Sensory evaluation of control and irradiated (2 kGy)carrot samples. Sensory analysis of control and irradiatedcarrot samples was done after 24 h of storage at 8 °C to 10 °C.Ordinate indicates 7-point hedonic scale (1 = very poor,2 = poor, 3 = fair, 4 = satisfactory, 5 = good, 6 = very good,and 7 = excellent). Abscissa indicates sensory parameters.All data points are the average of 3 experiments in triplicates.The bar represents standard deviation.

Figure 4—Sensory evaluation of control and irradiated (2 kGy)cucumber samples. Sensory analysis of control and irradiatedcucumber samples was done after 24 h of storage at 8 °C to10 ° C. Ordinate indicates 7-point hedonic scale (1 = very poor,2 = poor, 3 = fair, 4 = satisfactory, 5 = good, 6 = very good,and 7 = excellent). Abscissa indicates sensory parameters.All data points are the average of 3 experiments in triplicates.The bar represents standard deviation. Different letters (a, b)indicate the values in columns are significantly different at 0.05level of significance as tested by paired t-test.

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Table 1—Color measurement of single set of carrot samples (control and 2 kGy) during the storagea

Days of L* a* b* Cab* hab*

storage Control 2 kGy Control 2 kGy Control 2 kGy Control 2 kGy Control 2 kGy

0 70.71 72.62 11.41 8.42 32.47 34.63 34.82 35.79 69.93 76.12±3.32 ±3.85 ±4.08 ±2.89 ±4.94 ±3.60 ±3.24 ±3.07 ±9.48 ±5.99

4 69.90 71.91 11.31 8.63 33.10 34.05 35.31 35.26 70.47 75.53±2.72 ±3.14 ±3.59 ±2.63 ±4.96 ±3.64 ±3.65 ±3.14 ±8.23 ±5.58

8 69.12 71.91 11.75 7.8 34.39 35.00 36.56 35.87 70.57 77.43±2.31 ±2.15 ±2.87 ±1.43 ±4.98 ±3.15 ±4.02 ±3.27 ±6.74 ±1.75

12 68.13 70.25 12.18 8.96 34.35 34.90 36.69 36.20 70.03 75.55±2.34 ±3.88 ±3.29 ±3.37 ±4.55 ±3.79 ±3.61 ±3.63 ±6.93 ±5.73

16 67.50 69.48 12.17 10.01 34.97 34.99 37.20 36.65 70.36 74.01±1.83 ±3.94 ±2.63 ±4.26 ±4.70 ±2.91 ±3.94 ±2.58 ±5.92 ±6.97

aMean of the observations for each parameter in a column for control samples was not found to be significantly different (P < 0.05) than for the 2-kGysamples, as analyzed by 1-way analysis of variance (ANOVA). The data represent mean ± standard deviation (SD), n (number of observations) = 10. In thisset of experiments, same sample was analyzed at different time points of storage.

be because of repetitive exposure of these samples to the surround-ing environmental condition while they were used for color mea-surement. Every time the samples were removed for analysis, thetemperature of the samples increased to about ambient tempera-ture (26 ° ± 2 ° C) during measurement.

The color values for different samples analyzed at different daysof storage are shown in Table 2. No significant change in L*, a*, b*,Cab*, and hab* values of the samples after irradiation as well as duringpost-irradiation storage was observed compared with unirradiatedcontrol samples (Table 2). In this case, for every time point, new sam-ples were analyzed and were discarded after the analysis. This pre-vented exposure of samples to temperature variation and hence, thedifference in the color values of these samples was negligible.

of the control carrot samples ranged from 5.1 to 6.5 kg, whereas thatof irradiated samples ranged from 4.8 to 5.1 kg. Thus, there was sig-nificant reduction in firmness of the peripheral region after exposureto gamma rays. During storage, there was significant increase(P < 0.05) in the firmness of the peripheral region of both control andirradiated samples.

Figure 6 shows the texture profile of the central and peripheralregion I of cucumber. As seen from the graph, the firmness of thecentral region is almost 50% less than that of the peripheral regions(Figure 6 and 7). The texture of both control and irradiated sam-ples was comparable, and the force values were within a range of 0.8to 1.0 kg. In this case, irradiation as well as storage period showedno significant effect (P < 0.05) on the texture. Figure 7 reflects thetexture profile of peripheral region II of control and irradiated cu-cumber samples. The profiles of both the peripheral region I (Figure6) and II (Figure 7) showed a similar pattern. The texture of controland irradiated samples in both cases was within a range of 2.1 to3.0 kg. Radiation processing had no significant effect (P < 0.05) onthe texture of both the peripheral regions of cucumber. It is inter-esting to note that during storage, the hardness of these peripheralregions increased significantly (P < 0.05) until 16 d. Chaudry andothers (2004) observed similar increase in firmness of the carrotsamples during 2 wk of storage. This increase in the firmness inboth carrot and cucumber samples could be attributed to the lossof moisture during the storage, leading to hardening of the tissue.

Color measurement of carrotColor measurement of carrotColor measurement of carrotColor measurement of carrotColor measurement of carrotTable 1 shows the color values for same samples analyzed at dif-

ferent days of storage. As seen from L* values, the lightness of thecontrol as well as irradiated samples was reduced to a negligibleextent during storage, and there was no significant change(P < 0.05) in lightness over a storage period of 16 d. Redness of thecontrol samples remained unaffected over the storage period.However, there was a slight but insignificant reduction (P < 0.05) inredness of irradiated samples from 11.4 to 8.4 (as seen from a* val-ues), which showed no further decrease during post-irradiationstorage. There was no change (P < 0.05) in the yellowness as well aschroma values of the sample immediately after irradiation and alsoduring post-irradiation storage, as can be seen from b* and Cab*values. The b* values of both control as well as irradiated sampleswere in the range of 32.4 to 34.9 and 34.0 to 35.0, respectively;whereas the Cab* values of both control and irradiated sampleswere in the range of 34.8 to 37.2 and 35.2 to 36.6, respectively.There was a slight increase in the hue angle from 69.9 to 76.1 afterirradiation. Slight change in redness and hue angle observed could

Figure 7—Texture analysis of peripheral region II of con-trol and irradiated (2 kGy) cucumber samples. Textureanalysis of control and irradiated cucumber samples wasdone at peripheral region in between 2 placenta on theday of irradiation and every 4th d of storage until 16 d,using Instron Universal Testing Instrument. Ordinate indi-cates force in kg measuring resistance to the penetrationimposed by the sample to the probe. Abscissa indicatesday of storage. All data points are average of 3 experimentsin triplicates. The bar represents standard deviation. Dif-ferent letters across the line (a to e) indicate the forcevalues are significantly different over a storage period at0.05 level of significance as tested by 1-way analysis ofvariance (ANOVA).

Vol. 71, Nr. 3, 2006—JOURNAL OF FOOD SCIENCE S203

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URLs and E-mail addresses are active links at www.ift.org

Radiation hygienized carrot and cucumber . . .

Conclusions

The present study was an effort to generate data on the effect ofradiation processing on different quality parameters of mini-

mally processed carrot and cucumber. In both carrot and cucum-ber, irradiation had no significant effect (P < 0.05) on total vitaminC content, total carotenoids content (in carrot), or color of thesesamples. Textural studies carried out also revealed no significantdifference in texture except the peripheral region of carrot, whichshowed significant decrease in firmness after irradiation. Howev-er, this had no effect on its acceptability. Sensory evaluation did notshow significant change in quality attributes of carrot but showedsignificant change in odor and taste of cucumber samples after ir-radiation, which was within acceptable limits. The storage periodhad no significant effect (P < 0.05) on total vitamin C content ofcucumber, total carotenoids, or color of carrot samples. However, asignificant decrease was observed in vitamin C content of bothcontrol and irradiated carrot samples. The texture of carrot andcucumber samples showed significant increase in firmness duringthe entire storage, which can be attributed to the loss of moisturefrom the tissue. Thus, the present studies demonstrated that radi-ation processing of minimally processed carrot and cucumber didnot significantly affect the nutritional and sensory properties.However, this work deals with local varieties of carrot and cucumberavailable in a Mumbai market. Agroclimatic conditions and varietaldifference may change the nutrient composition of the salads andmay induce differential response to radiation processing. There-fore, further studies with other varieties from different geograph-ical locations need to be done. Nevertheless, these data will beuseful for supermarkets and other hotel industries dealing withsupply and utilization of minimally processed foods.

AcknowledgmentsThe study was carried out under Coordinated Research Project(Research Contract nr 11650) partly financed by Intl. Atomic EnergyAgency (IAEA), Vienna. The able laboratory assistance of K. Bagadeand N. Bhadrige is acknowledged.

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Table 2—Color measurement of different sets of carrot samples (control and 2 kGy) during the storagea

Days of L* a* b* Cab* hab*

storage Control 2 kGy Control 2 kGy Control 2 kGy Control 2 kGy Control 2 kGy

0 70.81 70.88 11.15 11.02 31.10 33.20 33.41 35.30 69.98 70.67±4.51 ±2.75 ±4.31 ±3.04 ±3.79 ±5.84 ±2.91 ±4.32 ±8.75 ±8.64

4 69.32 69.67 10.17 11.30 32.96 34.08 34.79 36.42 72.46 70.94±4.36 ±2.96 ±3.91 ±4.87 ±3.72 ±5.56 ±2.71 ±3.94 ±7.92 ±10.33

8 69.20 69.33 11.28 10.91 35.48 31.72 37.48 33.94 72.01 70.55±3.16 ±4.35 ±3.49 ±4.42 ±3.84 ±3.84 ±2.61 ±2.37 ±7.21 ±9.23

12 69.23 67.89 11.01 11.11 35.55 33.70 37.57 35.86 72.79 71.54±4.78 ±4.40 ±5.05 ±4.90 ±2.59 ±4.35 ±1.96 ±3.74 ±8.37 ±8.73

16 69.32 69.45 11.38 10.87 33.82 33.54 35.98 35.63 70.96 71.54±1.08 ±1.06 ±0.62 ±0.50 ±1.51 ±1.21 ±1.45 ±1.08 ±1.14 ±1.43

aMean of the observations for each parameter in a column for control samples was not found to be significantly different (P < 0.05) than for the 2-kGysamples, as analyzed by 1-way analysis of variance (ANOVA). The data represent mean ± standard deviation (SD), n (number of observations) = 10. In thisset of experiments, different samples were analyzed at different time points of storage.