Retention of storage quality and post-refrigeration shelf-life extension of plum (Prunus domestica L.) cv. Santa Rosa using combination of carboxy methyl cellulose (CMC) coating and

Radiation Physics and Chemistry 107 (2015) 136–148

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Retention of storage quality and post-refrigeration shelf-life extensionof plum (Prunus domestica L.) cv. Santa Rosa using combination ofcarboxymethyl cellulose (CMC) coating and gamma irradiation

Peerzada R. Hussain n, Prashant P. Suradkar, Ali M. Wani, Mohd A. DarAstrophysical Sciences Division, Nuclear Research Laboratory, Bhabha Atomic Research Centre, Zakura, Srinagar 190006, India

H I G H L I G H T S

� Irradiation and CMC alone at 1.5 kGy and 1.0% gave 8 and 5 days extension in shelf life.
� Treatment of 1% w/v CMCþ1.5 kGy inhibited decay up to21 days of ambient storage.� Combination of 1% CMC and 1.5 kGy irradiation extended shelf-life of plum by 11 days.� Combination treatment can help fruit marketing in glut season and enabling good returns.
a r t i c l e i n f o

Article history:Received 29 May 2014Received in revised form8 October 2014Accepted 18 October 2014Available online 25 October 2014

Keywords:PlumEdible coatingGamma irradiationStorage qualityShelf-life extension

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esponding author. Fax: þ91 1942422420.ail address: [email protected] (P.R. Hu

a b s t r a c t

Carboxymethyl cellulose (CMC) coatings alone and in combination with gamma irradiation was tested formaintaining the storage quality and extending shelf-life of plum. Matured green plums were CMC coatedat levels 0.5–1.0% w/v and gamma irradiated at 1.5 kGy. The treated fruit including control was storedunder ambient (temperature 2572 °C, RH 70%) and refrigerated (temperature 371 °C, RH 80%) con-ditions. In fruits treated with individual treatments of 1.0% w/v CMC; 1.5 kGy irradiation and combinationof 1.0% w/v CMC and 1.5 kGy irradiation, no decay was recorded up to 11, 17 and 21 days of ambientstorage. Irradiation alone at 1.5 kGy gave 8 days extension in shelf-life of plum compared to 5 days by1.0% w/v CMC coating following 45 days of refrigeration. All combinatory treatments of CMC coating andirradiation proved beneficial in maintaining the storage quality as well as delaying the decaying of plumduring post-refrigerated storage at 2572 °C, RH 70% but, combination of CMC at 1.0% w/v and 1.5 kGyirradiation was found significantly (pr0.05) superior to all other treatments in maintaining the storagequality and delaying the decaying of plum. CMC coating of plums at 1.0% w/v followed by irradiation at1.5 kGy resulted in chlorophyll retention of 19.4% after 16 days compared to 10% in control after 8 days ofambient storage. Under refrigerated conditions, same treatment gave retention of 67.6% in chlorophyllcompared to 10.6% in control after 35 days of storage. The above combinatory treatment resulted inextension of 11 days in shelf-life of plum during post-refrigerated storage at 2572 °C, RH 70% following45 days of refrigeration. Based on microbial analysis, irradiation alone at 1.5 kGy and in combination with1.0% w/v CMC resulted in 2.0 and 1.8 log reduction in yeast and mold count of plum fruit after 20 and 35days of ambient and refrigerated storage, thereby ensuring consumer safety.

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1. Introduction

Plum is highly perishable climacteric stone fruit and has shortshelf-life at optimal temperatures. Decay of plum fruit due to rapidripening and mold growth is a major problem during storage.Short shelf-life of the fruit represents a serious constraint forefficient handling, transportation and marketing chain of the

ssain).

produce. Quick softening after harvest and subsequent microbialinfestation lead to losses in the marketing chain. Although, lowtemperature storage of plum is recommended to extend fruitpostharvest life and maintain quality (Wang, 1993); however, ex-tended storage of plums at low non-freezing temperature leads tophysiological disorders like abnormal fruit ripening, developmentof chilling injuries such as internal and external browning, fleshbreakdown, reddish discoloration, increased incidence of decayand loss in consumer acceptance (Guerra and Casquero, 2008;Manganaris et al., 2008). The use of conventional chemicals as

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P.R. Hussain et al. / Radiation Physics and Chemistry 107 (2015) 136–148 137

anti-ripening, anti-senescence and microbial fumigants has beenphased out and restricted throughout the world. These chemicalspose serious health hazards and environmental effects (Cetinkayaet al., 2006). The adverse effects of these chemicals lower or limitthe export capabilities of fresh as well as dried fruits. To overcomethe adverse effects posed by the chemicals and at the same timeextend the shelf-life and maintain storage quality of fresh fruits,alternate processes are needed.

Gamma irradiation has become an effective means of proces-sing and preserving food products (Molins, 2001; Fan et al., 2003).The process is gaining much importance as it can be performed atroom temperature; and due to its cold nature and high efficiencyfor inactivation of food borne pathogens and parasites (Bidawidet al., 2000). Irradiation has been recognized as an alternative tochemicals for treating fresh and dried agricultural products toovercome quarantine barriers in international trade, as a mode ofdecontamination, disinfestations, delaying the ripening andsenescence of fruits and vegetables and for improving nutritionalattributes and shelf-life (McDonald et al., 2012; Hong et al., 2008;Lacroix and Ouattara, 2000; Hallman, 2000). Literature revealsthat gamma irradiation dose of 0.5–1.0 kGy was shown to extendthe storage life of plum without any significant difference in color,aroma and texture (Moy et al., 1982). Our earlier study (Hussainet al., 2013) also confirmed that gamma irradiation in the doserange of 1.2–1.5 kGy was effective in inhibiting the decay of plumand extending the storage life of fruit by 8 days at 2572 °C, RH70% following 35 days of refrigeration.

The preservation of fresh produce can also be achieved by theapplication of edible coatings. Edible coatings can be used toprotect perishable food products from deterioration by retardingdehydration, providing a selective barrier to moisture, oxygen andcarbon dioxide, suppressing respiration, improving textural qual-ity, helping retain volatile flavor compounds and reducingmicrobial growth (Lee et al., 2003). Polysaccharide based coatingshave been studied to extend the shelf-life of fruits andvegetables (Nisperos-Carriedo, 1997). Edible coatings based onpolysaccharide materials such as mixtures of starch, carrageenanand chitosan (Ribeiro et al., 2007), chitosan (Han et al., 2004),amylase (Garcia et al., 1998a, b) and carboxymethyl cellulose(Amarante and Banks, 2001; Maftoonazad et al., 2008) have beeninvestigated for delaying ripening, senescence and decay and fortheir beneficial effect in maintaining fruit quality when applied ascoatings.

Combinatory treatments have also widely been investigated asthey often result in synergistic effects. Earlier reports indicate thatedible coatings in combination with radiation processing hasshown significant delay in mold growth and microbial con-tamination level, leading thus to an improvement of the foodshelf-life (Lacroix et al., 2002; Vachon et al., 2003; Zuniga et al.,2012). CMC-based coatings can also be combined with gammairradiation to obtain a synergistic effect with respect to storagequality and shelf-life of fresh fruits. Therefore, the present studywas undertaken to evaluate the combined effect of gammairradiation and CMC coating on the storage quality and shelf-lifeextension of plum. The assessment of the treatments is based onthe evaluation of physic-chemical parameters, microbial load anddecay percentage.

2. Materials and methods

2.1. Raw material preparation

Plum fruits of uniform shape and size, firm texture, and propermaturity were procured from the local plum orchards of Shalimar,Kashmir. Selection of fruit was done from the same orchard. Fruit

was pre-cooled by keeping at 2 °C for 24 h in a cold storagechamber in order to remove field heat. The pre-cooled fruit wasmanually graded in order to have uniformity in size and anyblemished or diseased fruits present were discarded.

2.2. CMC coating

The coating treatment was given alone and in combination withgamma irradiation. The coating consisted of 0.5, 0.75 and 1.0%(w/v) CMC. The formulations were prepared by dissolving therequired quantity of CMC in distilled water under stirring andheating at 90 °C for 30 min. The solution was then cooled to roomtemperature. The fruits were dipped for 5–10 min at room tem-perature. The temperature of the coating solution was 1072 °C.After completion of the coating treatment, the samples were takenout and allowed to surface dry completely at 2572 °C using wallmounted fans. Following the CMC treatment, the fruits werepacked in cardboard boxes of size 0.5�0.3�0.3 m3. Three boxeseach containing 25 fruits were taken for each treatment persampling period. Fruits neither CMC coated nor gamma irradiatedserved as control.

2.3. Gamma irradiation treatment

The packaged CMC coated fruit was subjected to gamma irra-diation at 1.5 kGy using PANBIT irradiator (Isotope Division, BARC,Mumbai, India) having Co-60 as the gamma-ray source. The fruitswere irradiated at minimum dose rate of 128 Gy/h. To ensureuniformity of dose, boxes were turned by 180° half way throughthe irradiation time and the over dose ratio (Dmax/Dmin) was de-termined and found to be 1.6. The dose rate was determined byCeric-Cereous dosimetry. To ensure that fruit receives the exactdose, the dosimeters were placed in each fruit box for eachtreatment at high as well as low dose spots. After completion ofirradiation, separate batches of fruit either CMC coated only orCMC coated and gamma irradiated were kept under ambient(temperature 2572 °C, RH 70%) and refrigerated (temperature371 °C, RH 80%) storage conditions for periodic evaluation ofphysico-chemical parameters namely firmness, total sugars, ascor-bic acid, chlorophyll content, total anthocyanins, carbon dioxideevolution, weight loss, water soluble pectin (WSP), decay percen-tage, overall acceptability and microbial load as yeast and moldcount. Prior to the measurement of quality parameters all re-frigerated samples were allowed to attain the room temperature.Three boxes each containing 25 fruits were evaluated for eachparameter after every 4 days in case of ambient storage and every7 days in case of refrigerated storage.

2.4. Fruit analysis

2.4.1. FirmnessFirmness was determined with a hand penetrometer (Model

‘FT-327’ EFFEGI, Italy) provided with a round plunger (6 mm dia-meter) on two sides of each whole fruit. To avoid interference ofthe skin, fruits were peeled at positions where firmness was to bemeasured. Fruits were selected randomly, divided in triplicates andevaluated for firmness and mean value was expressed in kg.

2.4.2. Total sugarsTotal sugars were determined by modifying the method of

Miller (1959) using 3, 5-dinitrosalicylic acid reagent (DNSA). Thefruits initially used for firmness measurement were subjected tojuice extraction for estimation of total sugars. In principle, thereducing sugars reduce DNSA to 3-amino-5nitrosalicylic acidresulting in the formation of reddish-orange coloration that ismeasured with a spectrophotometer at 540 nm. A total of 5 ml of

P.R. Hussain et al. / Radiation Physics and Chemistry 107 (2015) 136–148138

filtered plum juice was mixed with equal amount of DNSA solutionand incubated on boiling water bath for 10 min. The mixture wasallowed to cool at ambient temperature and diluted further withdouble distilled water if required. The absorbance of the solutionwas measured at 540 nm using an ultraviolet–visible spectrometer(HITACHI-330, Germany). Glucose solution of known concentra-tion was used as standard for measuring the concentration ofreducing sugars in the juice sample. The estimation of total sugarswas performed following the inversion of sucrose (a non-reducingsugar) to reducing sugar. To 50 ml of plum juice, 2 g citric acid wasadded and the mixture was incubated at 60 °C for 20–30 min forcomplete inversion of sucrose to reducing sugars. The acidhydrolyzed solution was cooled to ambient temperature andneutralized by the addition of sodium hydroxide. From thishydrolyzed solution, 5 ml of the sample was taken for quantifyingtotal sugars in terms of invert sugar as per the method describedabove. Measurements were performed in triplicates. Sucrose andtotal sugar concentrations in juice sample were calculated usingthe equations:

= –

×

= +

Sucrose(%) (Total invert sugar Reducing sugar)

0.95Total sugar(%)

Reducing sugar(%) Sucrose(%)

2.4.3. Total anthocyaninsTotal anthocyanins were determined according to the pH- dif-

ferential method (Giusti and Wrolstad, 2001). Homogenized fruitsample in triplicates were extracted using ethanol: 1 N HCl (85:15,v/v). Clear extract (1 ml) was placed into 25 ml volumetric flask,made up to a final volume with pH 1.0 buffer (1.49 g of KCl /100 mlwater and 0.2 N HCl, with a ratio of 25:67) and mixed thoroughly.Another 1 ml of extract was also placed into a 25 ml volumetricflask, made up to a final volume with pH 4.5 buffer (1.64 g ofsodium acetate/100 ml of water, adjusted to pH 4.5 with 0.2 N HCl)and mixed. Absorbance was calculated as ΔA¼(A510 nm�A700 nm)pH1.0–(A510 nm�A700 nm) pH4.5 with a molar extinction coefficientof 26,900 for cyaniding 3-glucoside. Results were calculated usingthe following equation and expressed as mg of cyaniding 3-glucoside equivalents per 100 g of fresh sample.

= Δ × × ×A L MW D V GTotal anthocyanins(mg/100 g) ( /€ ) ( / )

Where ΔA is absorbance, € the cyaniding 3-glucoside molar ex-tinction coefficient (26,900), L the cell path length (1 cm), MW themolecular weight of anthocyanins (449.2), D a dilution factor, Vthe final volume (ml) and G the sample weight (g).

2.4.4. ChlorophyllChlorophyll was determined spectrophotometrically using the

method of Witham et al. (1971). Fruits were taken randomly anddivided in triplicates. The replicate fruits were peeled and knownweight of homogenized peel was extracted with 80% acetone. Theextraction was repeated till the residue was colorless. The extractswere collected and centrifuged at 14000 rpm for 14 min. Thecollected supernatants were volume made up to 100 ml with 80%acetone. The absorbance of the sample was read at 645 and663 nm against the 80% acetone as blank. The total chlorophyllwas calculated using the equation:

= + × × ×A A V W

Total chlorophyll(mg/100 g)

{20.2( ) 8.02( ) 100}/1000645 663

Where A¼absorbance at specific wavelengths, V¼volume madeup of chlorophyll extract in 80% acetone, W¼weight of sampletaken.

2.4.5. Water soluble pectin (WSP)Contents of water soluble pectin were determined by modify-

ing the method of Ranganna (1986). A sample size of known weightwas first extracted with 100 ml of 95% ethanol. The residue leftafter alcoholic extraction was dried at 30 °C. To obtain WSP, 30 g ofthe left over alcoholic insoluble solids (AIS) were extracted in250 ml of boiling water for 30 min. The extract was filtered,cooled, and volume made up to 250 ml with double distilledwater. A total of 100 ml aliquot of the filtrate was precipitated for1 h with 25 ml of calcium chloride (1 N). The precipitate obtainedwas dried and weighed in order to calculate the amount of WSPas:

=× ×

×

Water soluble pectin (%AIS)

Wt. of ppt (g) Volume made (ml) 100Wt. of sample (g) Aliquot taken (ml)

2.4.6. Carbon dioxide measurementAmount of carbon dioxide released during storage was mon-

itored by carbon dioxide analyzer (TES-1370, ISR Instruments,Belgium) provided with a dual wavelength IR detector with non-dispersive infrared (NDIR) sensor. The detector had sensing rangeof 0–7000 ppm and resolution of 1 ppm. The analyzer measurescarbon dioxide concentration by absorption of a specific wave-length in the infrared (IR) by the carbon dioxide molecules. Non-dispersive infrared absorption sensor consists of four elements:the light source, the detector element (e.g. light detector element),the optical path and the mechanical chopper. Known weight of fruitwas placed in a sealed suction type desiccators provided withrubber tubing as outlet. The desiccators were incubated for 1 h at2572 °C in case of ambient samples and 371 °C in case of re-frigerated samples. After the incubation period the rubber tubingof the desiccators was directly connected to the carbon dioxideanalyzer for taking the reading and the amount of carbon dioxidereleased was expressed as ppm/kg/h.

2.4.7. Ascorbic acid contentAscorbic and dehydroascorbic acid estimation was done by

HPLC system of JASCO, Japan (model, LC-Net II/ADC), fitted with anautomatic degassing unit, UV-2070 detector, PU-2080 pump and aHiQ-Sil C18 column (size 4.6 mm�250 mm) using the method ofPasternak et al. (2005). Known weight of sample of plum fruit intriplicates was extracted with 3% meta-phosphoric acid. The ex-traction procedures were repeated three times. The extracts fromeach replicate were pooled and filtered through Whatman filterpaper no. 42. Filtrate obtained was evaporated approximately toone-fourth of volume under nitrogen. The resultant sample wasthen filtered through 0.22 mm membrane filters (Millipore). Analiquot of 20 ml sample was injected for estimation purposes in aC-18 column. Prior to analysis, the analytical column was thor-oughly washed with methanol followed by mobile phase for 1 h.The mobile phase consisted of 2% acetic acid and the run wasisocratic. Flow rate of mobile phase was maintained at 0.5 ml/min.Detector wavelength was set at 254 nm. An external standard ofL-ascorbic acid and dehydroascorbic acid in 3% meta-phosphoricacid was used for the identification and quantification of ascorbicand dehydroascorbic acid, Ascorbic and dehydroascorbic acidcontent in plum samples were calculated from the standard curveof L-ascorbic and dehydroascorbic acid.

2.4.8. Weight lossWeight loss was determined by periodical weighing of samples.

Each sample consisting of 10 fruits were used for each treatmentincluding control. Weight loss was calculated from initial weight


using the formula:

= – ×W W WWeight loss (%) ( / ) 100i s i

Where Wi¼ initial weight; Ws¼weight at sampling period.

2.4.9. Decay percentageDecay percentage was determined visually from known number

of fruits. Any fruit showing the signs of fungal growth andmealiness (extreme soft and oozing condition) was considered asdecayed. Decay percentage was monitored under ambient(temperature 2572 °C, RH 70%), refrigerated (temperature371 °C, RH 80%) as well as post-refrigerated storage conditions(temperature 2572 °C, RH 70%). Two replicates of known numberof fruits were used for monitoring decay under ambient andrefrigerated conditions for each treatment including control. Formonitoring decay under post-refrigerated conditions, samples in-itially kept under refrigerated conditions were taken out from coldstorage and stored under ambient conditions to monitor decay.Decay percentage was calculated as:

=

×

Decay percentage (No. of decayed fruits/Total number of fruits)

100

2.4.10. Overall acceptability (OAA)Overall acceptability based on color, texture and taste was done

by a trained panel of eight judges on round table basis using4 point scale where 4¼excellent, 3¼good, 2¼fair and 1¼poor.Out of the eight judges, six were from the Division of Food Tech-nology, Sheri Kashmir university of Agricultural Sciences andTechnology, Kashmir (SKUAST-K) and two from our Nuclear Re-search Laboratory, having good experience in the sensory analysisof foods. The judges from the SKUAST-K were not associated withthe project. Twenty fruits were selected randomly, coded andserved to eight trained judges for evaluation of color, texture andtaste. The limit of acceptability was kept as 2.5 and the sampleswhose acceptability values were below 2.5 corresponding thestorage period were rated un-acceptable. The testing was under-taken in a place free from extraneous odors and sound. Panelistswere requested not to talk during the procedure. The panel testwas carried out under normal light conditions. The temperature ofthe fruit during testing was the existing normal temperature. Thepanelists were instructed to evaluate the taste of the samples byeating the samples and assign the score as per the 4 point scale.The overall acceptability was reported as the mean of the triplicatevalues of color, texture and taste. The OAA of the samples whichexhibited retention in green color, crisp texture and acceptabletaste was rated higher than the samples which recorded decreasein green color, mealy like texture and bitter or insipid taste.

2.4.11. Yeast and mold countYeast and mold count was determined by pour plate technique

using potato dextrose agar media (Aneja, 1996). Plum fruits intriplicates were homogenized in a homogenizer (HL-1631, Philips,India). Known weight of homogenized sample was taken and dis-solved in previously sterilized 9 ml of distilled water and kept instirring for 30 min. One milliliter of this solution was further di-luted by dissolving in 9 ml of sterilized distilled water. This way adilution of 10�3 was obtained. One milliliter aliquot each of 10�3

dilutions was pour-plated in triplicates on potato dextrose agarmedia to determine yeast and mold count. The samples were in-cubated at 3072 °C for 5 days. The colonies so formed werecounted and expressed as log cfu/g of sample. Triplicate sampleswere used for the determination of yeast and mold count and limitof detection was 1 cfu/g of sample.

2.5. Statistical analysis

The data was analyzed statistically using completely rando-mized design experiment (Cochran and Cox, 1992). For eachmeasurement, three replicates of samples were tested per treat-ment and mean7standard deviation values were reported.Triplicate samples each consisting of 20 fruits were used formeasurement of firmness and total sugars. For anthocyanindetermination 3 g of sample per replicate was used. For chlor-ophyll analysis, fifteen fruits were taken randomly and divided intriplicates with each replicate consisting of five fruits. The fruitswere peeled and 3 g of homogenized peel was extracted with 80%acetone. Triplicate sample each consisting of 50 g was used fordetermination of water soluble pectin. Carbon dioxide content wasmeasured on triplicate basis by taking 1 kg of fruit per replicate.For ascorbic acid analysis, 10 g of sample per replicate was used forextraction. Two replicates of 70 fruits each consisting of 35 wereused for monitoring decay of plum during storage. For microbialanalysis, fifteen fruits in triplicates each consisting of five fruitswere homogenized and one gram of homogenized sample wasused. Analysis of variance (ANOVA) of the data was performedusing MINITAB statistical analysis software package (Minitab,version 11.12, 32 bit, Minitab, USA). Difference between means ofdata was compared by least significant difference (LSD) and Stu-dent's t-test was applied to determine if the difference was statis-tically significant among the treatments and storage period. Differ-ences at pr0.05 were considered to be statistically significant.Duncan's multiple range test was used to compare the meanvalues at each storage period. Coefficient of correlation wasdetermined by Karl Pearson method.

3. Results and discussion

3.1. Firmness and water soluble pectin (WSP)

Effect of individual and combination treatments of CMC coatingand gamma irradiation on firmness and WSP is shown inFigs. 1 and 2 respectively. Data analysis revealed no significant(p40.05) difference in firmness of plum fruits treated individuallyor in combination with CMC and gamma irradiation at the first dayof storage under both the storage condition. Further it is clear fromthe Fig. 1 that firmness of plum decrease during the storage time.The decrease was significantly (pr0.05) higher in samples keptunder ambient conditions than under refrigerated condition. Dataanalysis also revealed that under refrigerated conditions, firmnessdecrease was statistically non-significant (p40.05) up to 14 daysof storage in samples treated with combination of CMC coating at0.75 and 1.0% w/v and 1.5 kGy irradiation. Among coating treat-ments, 0.5% w/v CMC had no significant effect on preventingfirmness decrease when compare with control irrespective ofstorage condition. Treatments of irradiation alone at 1.5 kGy, CMCcoating at levels above 0.5% w/v and combination of irradiation(1.5 kGy) and CMC coating at levels 0.5% to 1.0% w/v showed sig-nificant (pr0.05) beneficial effects in maintaining the highervalves of firmness of plum under both the storage conditions.Among the combinatory treatments, CMC coating (1.0% w/v) fol-lowed by irradiation at 1.5 kGy maintained significantly (pr0.05)higher firmness of plum under both the storage conditions. After16 and 20 days of ambient storage, firmness was below the limit ofdetection for control, 0.5% w/v and 0.75% w/v CMC coated fruitswhich is related to excessive softening of the fruit due to enzymemediated solubilization of pectic substances as a result of ripening.The extent of firmness decrease for control, 0.5% and 0.75% w/vCMC plum fruits were of the order of 81.4%, 78% and 85.1%respectively after 12 and 16 days of ambient storage. In fruits

0

2

4

6

8

10

12

14

0 4 8 12 16 20

Firm

ness

(kg)

Storage period (days)

T1T2T3T4T5T6T7T8

0

2

4

6

8

10

12

14

0 7 14 21 28 35

Firm

ness

(kg)


T1T2T3T4T5T6T7T8

Fig. 1. Firmness of Plum fruit treated with CMC coating and gamma irradiationduring storage under ambient (a) and refrigerated (b) conditions. T1¼ control;T2¼0.5% w/v CMC; T3¼0.75% w/v CMC; T4¼1.0% w/v CMC; T5¼1.5 kGy; T6¼0.5%w/v CMC, 1.5 kGy; T7¼0.75% w/v CMC, 1.5 kGy; T8¼1.0% w/v CMC, 1.5 kGy;CMC¼carboxymethyl cellulose.

0

0.5

1

1.5

2

2.5

3

0 4 8 12 16 20

Wat

er so

lubl

e pe

ctin

(% A

IS)


T1T2T3T4T5T6T7T8

0

0.5

1

1.5

2

2.5

3

0 7 14 21 28 35

Wat

er so

lubl

e pe

ctin

(% A

IS)


T1T2T3T4T5T6T7T8

Fig. 2. Effect of CMC coating and gamma irradiation treatments on water solublepectin content of Plum fruit during storage under ambient (a) and refrigerated(b) conditions. T1¼ control; T2¼0.5% w/v CMC; T3¼0.75% w/v CMC; T4¼1.0% w/vCMC; T5¼1.5 kGy; T6¼0.5% w/v CMC, 1.5 kGy; T7¼0.75% w/v CMC, 1.5 kGy;T8¼1.0% w/v CMC, 1.5 kGy; CMC¼carboxymethyl cellulose.


treated with individual treatments of 1.0% w/v CMC and 1.5 kGy,firmness decreased by 85.9% and 74.4% after 20 days of ambientstorage. In fruits treated with combination treatments of coating(0.5–1.0% w/v CMC) and gamma irradiation (1.5 kGy), firmnessdecrease after 20 days of ambient storage was in the range of 52.4to 68.6% and was significantly (pr0.05) lower in samples sub-jected to combination of 1.0% w/v CMC and 1.5 kGy gamma irra-diation. Under refrigerated condition after 35 days, firmnessdecrease by 63.8% for control fruits, 50.0 to 59.5% for fruits coatedwith CMC in the range of 0.5–1.0% w/v and 46.3% for fruits irra-diated at 1.5 kGy respectively. In fruits treated with combinationtreatments of CMC and gamma irradiation, firmness decease re-corded after 35 days of refrigerated storage was in the range of20.5–31.6% and was significantly (pr0.05) lower in fruits treatedwith combination of 1.0% w/v CMC and 1.5 kGy irradiation. Datapresented in Fig. 2 revealed that WSP increased in all the samplesand the increase was significantly higher (pr0.05) in fruits storedunder ambient conditions compared to refrigerated conditions. Itis clear from the Fig. 2 that WSP increase was statistically non-significant (p40.05) up to 7 days of refrigerated storage in sam-ples treated with combination of CMC coating at 0.5–1.0% w/v and1.5 kGy irradiation. Fig. 2 also revealed that in control and 0.5% w/vCMC coated samples stored under ambient conditions; WSPreached it is maximum value after 8 days followed by a decrease.In case of samples treated with individual treatments of 0.75 and1.0% w/v CMC; 1.5 kGy irradiation and combination of 0.5% w/vCMC and 1.5 kGy irradiation this trend in WSP was observed after12 and 16 days of ambient storage respectively. In samples treatedwith combination of CMC coating (0.75–1.0% w/v) and 1.5 kGy ir-radiation, WSP continued to increase up to 20 days of storage. On

the other hand, under refrigerated conditions, the WSP continuedto in increase up to 35 days of storage in all the treatments exceptin control and 0.5% w/v CMC coated samples where WSP increasedup to 28 days and then decreased. On the basis of the data plottedin Fig. 2, it can be inferred that under ambient storage; control and0.5% w/v CMC coated samples were almost fully ripe after 8 daysof ambient storage. Fruits treated with either individual treat-ments of 0.75 and 1.0% w/v CMC; 1.5 kGy irradiation and combi-nation of 0.5% w/v CMC and 1.5 kGy irradiation where almost fullyripe after 12 and 16 days of ambient storage. Under refrigeratedconditions, control and 0.5% w/v CMC coated samples were almostfully ripe after 28 days compared to all other samples. Decrease infirmness is associated with the conversion of insoluble pecticfraction to the soluble forms during ripening. During ripening, theactivities of enzymes namely protopectinase and pectin methy-lesterase responsible for hydrolyzing and solubilization of pecticsubstances increases, thereby contributing to firmness decreaseand subsequent increase in water soluble pectin. Since irradiationis known to delay the ripening and senescence of climacteric fruits(Fan et al., 2003) and combination with methods like CMC coatinggives a synergistic effect. Therefore, the significant retention offirmness in samples treated with combination of CMC (1.0% w/v)and 1.5 kGy irradiation stored under either of the two conditions isattributed to the reduction in the enzymatic activity due to ri-pening delay as a result of individual or synergistic effect of thetreatment (Kovacs et al., 1997; Prakash et al., 2002; Hussain et al.,2008). Our results also revealed that WSP was inversely correlatedwith the firmness (r¼ �0.89), thereby confirming the higherfirmness in samples treated with combination of CMC coating

Table

1Effect

ofco

mbinationtrea

tmen

tof

CMCco

atingan

dga

mmairradiation

ontotalsu

gars

ofplum

duringstorag

e.

Trea

tmen

tAscorb

icac

id(m

g/10

0g)

Ambientstorage

(day

s)Refrige

ratedstor

age(day

s)

04

812

1620

LSD

07

1421

2835

LSD

T16.67

0.21

a,1

10.47

0.21

d,3

11.87

0.24

d,5

12.27

0.32

e,6

11.27

0.22

c,4

9.47

0.20

a,2

0.4

6.47

0.22

a,1

8.27

0.18

b,2

10.67

0.21

d,3

11.47

0.30

d,4

12.27

0.26

d,5

11.27

0.18

c,3

0.6

T26.67

0.22

a,1

10.27

0.22

d,3

11.57

0.20

d,4

11.87

0.26

d,4

11.47

0.24

c,4

9.67

0.18

a,2

0.4

6.47

0.22

a,1

8.27

0.16

b,2

10.67

0.23

d,3

11.27

0.33

d,3

12.47

0.22

d,5

11.67

0.20

c,4

0.6

T36.67

0.21

a,1

10.47

0.14

d,2

11.27

0.25

c,3

11.87

0.22

d,3

11.67

0.26

d,3

9.87

0.20

a,2

0.6

6.27

0.22

a,1

7.87

0.16

b,2

9.27

0.28

c,3

10.27

0.31

c,4

10.87

0.25

c,4

11.67

0.22

c,5

0.8

T46.67

0.22

a,1

9.67

0.22

c,2

10.87

0.20

c,3

11.67

0.24

d,4

12.27

0.20

e,4

11.47

0.18

b,3

0.6

6.27

0.22

a,1

7.87

0.13

b,2

8.67

0.26

b,3

9.67

0.33

b,4

10.67

0.30

c,5

11.47

0.24

c,6

0.5

T56.97

0.22

a,1

8.27

0.22

b,2

9.27

0.14

b,3

10.47

0.21

c,4

11.67

0.25

d,5

12.47

0.22

d,6

0.4

6.67

0.22

a,1

7.27

0.22

a,1

8.17

0.12

a,2

9.27

0.22

b,3

9.87

0.34

b,3

10.67

0.31

b,4

0.6

T66.87

0.22

a,1

8.27

0.12

b,2

9.27

0.14

b,3

10.27

0.22

b,4

11.47

0.20

c,5`

12.27

0.25

c,6

0.5

6.67

0.22

a,1

7.27

0.14

a,1

8.17

0.20

a,2

9.27

0.36

b,3

9.87

0.32

b,3

10.67

0.26

b,4

0.6

T76.97

0.22

a,1

8.27

0.22

b,2

8.87

0.14

b,3

9.87

0.22

b,4

10.87

0.18

b,5

11.87

0.16

c,6

0.4

6.67

0.22

a,1

7.27

0.12

a,1

7.87

0.22

a,2

8.67

0.31

a,3

9.67

0.28

b,4

10.47

0.20

b,5

0.6

T86.87

0.22

a,1

7.67

0.20

a,2

8.27

0.16

a,3

9.27

0.21

a,4

10.27

0.16

a,5

11.27

0.14

b,6

0.4

6.87

0.22

b,1

7.27

0.12

a,1

7.87

0.20

a,2

8.27

.34a

,28.87

0.31

a,3

9.67

0.21

a,4

0.5

LSD

0.3

0.3

0.4

0.4

0.2

0.4

0.4

0.4

0.3

0.4

0.5

0.4

Values

aremea

n7

SD,n

¼3;

LSD¼leastsign

ificantdifference

(pr

0.05

);CMC¼carbox

ymethy

lcellu

lose.

Values

within

trea

tmen

tsin

aco

lumnnot

sharingaco

mmon

superscriptlowercase

letter

(a–e)

aresign

ificantly(p

r0.05

)different.

Values

within

storag

eperiodsin

arow

not

sharingaco

mmon

superscriptnumerical

(1–6)

aresign

ificantly(p

r0.05

)different.

T1¼co

ntrol;T2

¼0.5%

w/v

CMC;T3

¼0.75

%w/v

CMC;T4

¼1.0%

w/v

CMC;T5

¼1.5kG

y;T6

¼0.5%

w/v

CMC,1.5

kGy.

T7¼0.75

%w/v

CMC,1.5

kGy;

T8¼1.0%

w/v

CMC,1.5

kGy.

0

1000

2000

3000

4000

5000

6000

7000

8000

4 8 12 16 20

Car

bond

ioxi

de r

elea

sed

(ppm

/kg/

h )


T1T2T3T4T5T6T7T8

0

5

10

15

20

25

30

35

7 14 21 28 35

Car

bon

diox

ide

rele

ased

(ppm

/kg/

h )

Storagr period (days)

T1T2T3T4T5T6T7T8

Fig. 3. Carbon dioxide content released by Plum fruit treated with CMC coating andgamma irradiation during storage. T1¼ control; T2¼0.5% w/v CMC; T3¼0.75% w/vCMC; T4¼1.0% w/v CMC; T5¼1.5 kGy; T6¼0.5% w/v CMC, 1.5 kGy; T7¼0.75% w/vCMC, 1.5 kGy; T8¼1.0% w/v CMC, 1.5 kGy CMC¼carboxymethyl cellulose.


(1.0% w/v) and irradiation (1.5 kGy) and stored under either of thetwo conditions.

3.2. Total sugars and carbon dioxide evolution

Effect of CMC coating and irradiation processing on total sugarsand carbon dioxide evolution of plum fruit is shown in Table 1 andFig. 3 respectively. It is seen from the data presented in Table 1that no significant (p40.05) difference existed in total sugarsamong the treatments at first day of storage. During storage underambient conditions, total sugars of control and CMC coated fruitsfirst increase to its maximum value followed by a decrease to-wards the end of storage. In case of control, 0.5 and 0.75% w/v CMCcoated fruits; total sugars reached its maximum value after 12 daysof ambient storage followed by a decrease. The percentage in-crease in total sugars after 12 days was of the order of 84.4% and78.8% in control, 0.5 and 0.75% w/v CMC coated fruits respectively.In fruits treated with 1.0% w/v CMC, total sugars increased up to 16days (84.8%) followed by a decrease after 20 days of storage.However, in samples treated with irradiation alone at 1.5 kGy andin combination with CMC coating (0.5–1.0% w/v); total sugarscontinued to increase up to 20 days of ambient storage and theincrease was significantly lower of the order of 64.7% in fruitstreated with combination of 1.0% w/v CMC coating and 1.5 kGyirradiation compared to other treatments. After 20 days of ambientstorage, decrease in total sugars from the maximum value was22.9% in control and 6.6–18.6% in CMC coated fruits (0.5–1.0% w/v).Under refrigerated conditions, total sugars of all the samplescontinued to increase up to 35 days expect in control and 0.5% w/vCMC coated fruits, where total sugars reached its maximum valueafter 28 days followed by a decrease. This initial increase in totalsugars is attributed to either enzymatic induced conversion ofhigher polysaccharides into the simple sugars during ripening,whereas the subsequent decrease in sugar values is due tooxidative breakdown of sugars owing to respiration as well as utili-zation of sugars as substrates for fungal growth (Hussain et al., 2010;

Table

2Effect

ofco

mbinationtrea

tmen

tof

CMCco

atingan

dga

mmairradiation

onch

loroph

yllof

plum

duringstorag

e.

Trea

tmen

tAscorb

icac

id(m

g/10

0g)

Ambientstorage

(day

s)Refrige

ratedstor

age(day

s)

04

812

1620

LSD

07

1421

2835

LSD

T19.87

0.36

a,3

4.27

0.11

a,2

1.17

0.14

a,1

ND

ND

ND

1.4

10.47

0.36

a,6

8.27

0.28

a,5

6.37

0.31

a,4

4.17

0.35

a,3

2.37

0.17

a,2

1.17

0.18

a,1

1.0

T29.87

0.36

a,3

4.47

0.12

a,2

1.27

0.20

b,1

ND

ND

ND

1.5

10.27

0.36

a,5

8.67

0.26

a,4

6.97

0.33

a,3

4.57

0.35

a,2

2.77

0.21

a,1

1.67

0.20

a,1

1.1

T39.47

0.36

a,4

5.27

0.14

b,3

2.27

0.14

c,2

0.32

70.14

a,1

ND

ND

1.5

9.87

0.36

a,5

8.67

0.31

a,5

7.37

0.28

b,4

5.67

0.31

b,3

3.57

0.25

b,2

2.27

0.22

b,1

1.2

T49.67

0.36

a,4

6.57

0.22

c,3

3.27

0.15

d,2

0.64

70.14

a,1

ND

ND

2.1

10.37

0.34

a,5

9.17

0.33

b,4

8.27

0.26

c,4

6.27

0.33

b,3

4.67

0.30

c,2

3.27

0.24

c,1

1.2

T59.87

0.32

a,4

7.57

0.14

d,3

4.97

0.21

e,2

1.87

0.15

b,1

ND

ND

1.0

10.27

0.34

a,5

9.57

0.32

b,5

8.47

0.28

c,4

6.67

0.34

c,3

5.67

0.31

d,2

4.57

0.24

d,1

0.8

T69.67

0.32

a,4

7.87

0.12

d,3

5.27

0.24

e,2

2.57

0.25

b,1

ND

ND

1.6

10.27

0.36

a,5

9.57

0.34

b,5

8.37

0.24

c,4

7.17

0.36

c,3

6.17

0.32

d,2

5.27

0.26

d,1

0.7

T79.47

0.36

a,4

8.47

0.22

e,4

6.67

0.24

f,3

3.27

0.23

c,2

0.74

70.14

a,1

ND

1.4

9.87

0.34

a,4

9.27

0.32

b,4

8.37

0.31

c,3

7.77

0.31

d,3

6.87

0.28

e,2

5.97

0.20

e,1

0.6

T89.87

0.36

a,4

8.87

0.23

e,3

7.67

0.26

g,3

4.27

0.21

d,2

1.97

0.16

b,1

ND

1.5

10.27

0.36

b,4

9.87

0.38

b,4

8.87

0.28

c,3

8.27

.34d

,27.77

0.31

f,2

6.97

0.21

f,10.5

LSD

0.5

0.5

0.6

0.7

0.6

0.6

0.7

0.6

0.6

0.5

0.7

Values

aremea

n7

SD,n

¼3;

LSD¼leastsign

ificantdifference

(pr

0.05

);CMC¼carbox

ymethy

lcellu

lose;ND¼not

detected.

Values

within

trea

tmen

tsin

aco

lumnnot

sharingaco

mmon


letter

(a–g)

aresign

ificantly(p

r0.05

)different.

Values

within

storag

eperiodsin

arow

not

sharingaco

mmon


(1–6)

aresign

ificantly(p

r0.05

)different.

T1¼co

ntrol;T2

¼0.5%

w/v

CMC;T3

¼0.75

%w/v

CMC;T4

¼1.0%

w/v

CMC;T5

¼1.5kG

y;T6

¼0.5%

w/v

CMC,1.5

kGy.

T7¼0.75

%w/v

CMC,1.5

kGy;

T8¼1.0%

w/v

CMC,1.5

kGy.


Singh and Sudhakar Rao, 2005). Among the treatments, combi-nation of 1.0% w/v CMC coating and 1.5 kGy irradiation provedeffective in delaying the initial increase as well as decrease in totalsugars towards the end of storage compared to all other treat-ments under both the storage conditions, thereby indicating asignificant (pr0.05) delaying effect on the processes of ripening,senescence and respiration. The inhibitory effect of CMC coatingand gamma irradiation on the process of respiration and senes-cence measured via amount of carbon dioxide released duringstorage under ambient as well as refrigerated condition is shownin Fig. 3. It is clear from the Fig. 3 that carbon dioxide content ofcontrol and 0.5% w/v CMC coated samples; stored under ambientcondition recorded a decreasing trend as monitored after 8 days,thereby indicating the complete ripening of these fruits. The sig-nificant (pr0.05) increase in amount of carbon dioxide released asmonitored after 12 days indicates the outburst of senescence inthese fruits. From Fig. 3, it can be inferred that in samples treatedwith individual treatments of CMC coating (0.75 and 1.0% w/v),onset of senescence was observed after 12 days of ambient storageas against 16 days in samples treated with irradiation alone at1.5 kGy and in combination with 0.5% w/v CMC. In fruits treatedwith combination of CMC coating (0.75, 1.0% w/v) and 1.5 kGyirradiation, the release of carbon dioxide content continued toincrease up to 20 days of ambient storage. Under refrigeratedcondition, the delaying effect of the individual as well as combi-natory treatments on the processes of ripening and senescencewas more pronounced, which is attributed to the synergistic effectof treatments and low temperature storage. In control samples, theonset of senescence was observed after 28 days of storage asevident from the sudden up rise in the amount of carbon dioxidereleased following the decrease as monitored after 21 days. Sam-ples treated with CMC coating and irradiation either alone or incombination were not completely ripe over the entire period ofrefrigerated storage. Comparison of the treatments revealed thatcombination of CMC coating (1.0% w/v) and 1.5 kGy irradiation wassignificantly (pr0.05) effective in delaying the ripening andsenescence of the fruits throughout the entire period of storage.

3.3. Chlorophyll and anthocyanin content

Effect of CMC coating and gamma irradiation treatment onchlorophyll and anthocyanin content is shown in Table 2 and Fig. 4respectively. Data presented in Table 2 and Fig. 4 reveals no sig-nificant (p40.05) difference in chlorophyll and anthocyanin con-tents among the treatments at first day of storage. However, duringstorage decrease in chlorophyll content with concomitant increasein anthocyanins was observed in all the treatments under both thestorage conditions. The decrease in chlorophyll content and in-crease in anthocyanins was significantly (pr0.05) higher underambient storage compared to refrigerated storage. However,among treatments the increase in anthocyanins was statisticallynon-significant (p40.05) up to 4 and 8 days of ambient storage insamples treated with combination of CMC coating (0.75 and 1.0%w/v) and 1.5 kGy irradiation respectively. Similarly in samplestreated with combination of CMC coating treated with irradiationalone at 1.5 kGy and combination of CMC coating (0.5–1.0% w/v)and 1.5 kGy irradiation, the increase in anthocyanin content wasstatistically non-significant up to 14 and 21 days of refrigeratedstorage. Statistical analysis of the data also indicated that after4 days of ambient storage, chlorophyll content of control and 0.5%w/v CMC coated fruits was marginally (p40.05) different withrespect to one another but, significantly (pr0.05) lower comparedto other treatments. Under refrigerated conditions, similar trend inchlorophyll was recorded in control, 0.5 and 0.75% w/v CMCcoated samples after 7 days of storage. After 12 days of ambientstorage, chlorophyll content was not detected in control and

0

5

10

15

20

25

30

35

0 4 8 12 16 20

Ant

hocy

anin

s (m

g/10

0 g)


T1T2T3T4T5T6T7T8

0

5

10

15

20

25

0 7 14 21 28 35

Ant

hocy

anin

s (m

g/10

0 g)


T1T2T3T4T5T6T7T8

a

b

Fig. 4. Anthocyanin content of Plum fruit treated with CMC coating and gammairradiation during storage. T1¼ control; T2¼0.5% w/v CMC; T3¼0.75% w/v CMC;T4¼1.0% w/v CMC; T5¼1.5 kGy; T6¼0.5% w/v CMC, 1.5 kGy; T7¼0.75% w/v CMC,1.5 kGy; T8¼1.0% w/v CMC, 1.5 kGy; CMC¼carboxymethyl cellulose.

Table

3Effect

ofco

mbinationtrea

tmen

tof

CMCco

atingan

dga

mmairradiation

onasco

rbic

acid

ofplum

duringstorag

e.

Trea

tmen

tAscorb

icac

id(m

g/10

0g)

Ambientstor

age(day

s)Refrige

ratedstor

age(day

s)

04

812

1620

LSD

07

1421

2835

LSD

T19.47

0.15

a,5

5.87

0.21

a,4

2.97

0.14

a,3

1.77

0.15

a,2

1.17

0.12

a,1

0.73

70.10

a,1

0.4

9.47

0.12

a,6

7.77

0.28

a,5

5.47

0.22

a,4

3.37

0.20

a,3

1.87

0.16

a,2

0.94

70.15

a,1

0.6

T29.47

0.13

a,6

6.27

0.20

a,5

3.57

0.19

a,4

2.17

0.12

a,3

1.57

0.14

a,2

0.88

70.15

a,1

0.5

9.47

0.12

a,6

7.97

0.26

a,5

5.87

0.25

a,4

3.87

0.23

a,3

2.17

0.22

a,2

1.17

0.20

b,1

0.7

T39.67

0.22

a,6

6.87

0.18

b,5

4.27

0.15

b,4

2.67

0.12

b,3

1.97

0.15

b,2

1.02

70.10

a,1

0.5

9.67

0.15

a,6

8.17

0.19

b,5

6.27

0.28

b,4

4.27

0.21

b,3

2.57

0.25

b,2

1.57

0.22

c,1

0.7

T49.67

0.23

a,6

7.27

0.22

b,5

4.87

0.11

b,4

3.17

0.16

b,3

2.37

0.10

b,2

1.47

0.18

b,1

0.4

9.47

0.22

a,6

8.47

0.23

b,5

6.77

0.26

b,4

4.87

0.23

b,3

3.17

0.32

c,2

1.87

0.24

c,1

0.8

T59.27

0.16

a,6

7.67

0.16

c,5

5.47

0.14

c,4

3.87

0.21

c,3

2.77

0.15

c,2

1.87

0.12

c,1

0.6

9.17

0.12

a,5

8.77

0.32

c,5

7.47

0.22

c,4

5.57

0.25

c,3

3.87

0.22

d,2

2.47

0.20

d,1

0.8

T69.27

0.15

a,6

7.57

0.15

c,5

5.87

0.16

c,4

4.47

0.22

c,3

3.27

0.12

c,2

2.17

0.22

c,1

0.8

9.17

0.22

a,5

8.97

0.30

c,5

7.97

0.22

c,4

6.27

0.26

c,3

4.47

0.22

e,2

2.97

0.22

e,1

0.6

T79.27

0.14

a,6

8.17

0.19

d,5

6.57

0.18

d,4

5.17

0.20

d,3

3.87

0.20

d,2

2.67

0.23

d,1

0.8

9.27

0.12

a,5

8.97

0.25

c,5

8.47

0.25

d,4

6.87

0.28

d,3

5.17

0.28

f,2

3.37

0.15

f,1

0.6

Values

aremea

n7

SD,n

¼3;

LSD¼leastsign

ificantdifference

(pr

0.05

);CMC¼carbox

ymethy

lcellu

lose.

Values

within

trea

tmen

tsin

aco

lumnnot

sharingaco

mmon


letter

(a–g)

aresign

ificantly(p

r0.05

)different.

Values

within

storag

eperiodsin

arow

not

sharingaco

mmon


(1–6)

aresign

ificantly(p

r0.05

)different.

T1¼co

ntrol;T2

¼0.5%

w/v

CMC;T3

¼0.75

%w/v

CMC;T4

¼1.0%

w/v

CMC;T5

¼1.5kG

y;T6

¼0.5%

w/v

CMC,1.5

kGy.

T7¼0.75

%w/v

CMC,1.5

kGy;

T8¼1.0%

w/v

CMC,1.5

kGy.


0.5% w/v CMC coated fruits. Similar trend in chlorophyll wasrecorded in samples treated with individual treatments of CMCcoating (0.75 and 1.0% w/v), irradiation (1.5 kGy) and combinationof 0.5% w/v CMC coating and 1.5 kGy irradiation after 16 days ofstorage. After 20 days of ambient storage, chlorophyll was notdetected even in samples treated with combination CMC coating(0.75 and 1.0% w/v) and 1.5 kGy irradiation. Under refrigeratedconditions after 35 days of storage, the combinatory treatment ofcoating and irradiation as well as individual treatment of 1.5 kGyirradiation were significantly effective (pr0.05) in preventingchlorophyll degradation and subsequent anthocyanin accumula-tion in plum fruit compared to individual treatments of CMCcoating. The lost of chlorophyll during storage is attributed to thechange of chloroplasts into chromoplasts containing yellow andred pigments. The major loss of chlorophyll is mediated throughan increase in the activity of the enzyme chlorophyllase duringripening which degrade the molecule. The retention of highervalues of chlorophyll and reduction in anthocyanin increase incase of samples treated with combination of 1.0% w/v CMC and1.5 kGy irradiation can be attributed to the inhibitory effect of bothirradiation as well as CMC coating on the activity of chlorophyllaseand flavonoid glucosyltransferase enzymes involved in chlorophylldegradation and anthocyanin biosynthesis (Hussain et al., 2013),further the free radicals produced during irradiation may act asstress signals and may trigger some stress responses resulting inslower degradation of chlorophyll (Fan and Thayer, 2001).

Table

4Effect

ofco

mbinationtrea

tmen

tof

CMCco

atingan

dga

mmairradiation

onweigh

tloss

ofplum

duringstorag

e.

Trea

tmen

tW

eigh

tloss

(%)

Ambientstorage

(day

s)Refrige

ratedstor

age(day

s)

48

1216

20LS

D7

1421

2835

LSD

T19.67

0.25

e,1

17.57

0.23

f,2

22.47

0.14

g,3

26.17

0.25

g,4

28.37

0.32

g,5

1.5

3.97

0.15

c,1

5.47

0.28

d,1

10.97

0.22

g,2

16.57

0.20

g,3

21.27

0.16

g,4

1.5

T29.27

0.23

e,1

16.57

0.21

f,2

21.57

0.19

g,3

25.37

0.22

g,4

27.87

0.14

g,5

1.8

3.57

0.11

c,1

5.17

0.26

d,1

10.37

0.25

g,2

15.77

0.23

g,3

20.67

0.22

g,4

1.6

T38.67

0.20

d,1

15.17

0.20

e,2

20.27

0.15

f,3

24.27

0.32

f,4

26.87

0.35

f,5

2.1

3.37

0.18

c,1

5.17

0.15

d,1

9.57

0.28

f,2

14.67

0.21

f,3

19.87

0.25

f,4

1.8

T47.87

0.23

d,1

13.17

0.24

d,2

18.67

0.11

e,3

22.67

0.26

e,4

24.87

0.10

e,5

1.6

2.57

0.22

b,1

4.17

0.23

c,1

8.17

0.26

e,2

13.17

0.23

e,3

18.57

0.32

e,4

1.6

T56.77

0.15

c,1

10.37

0.16

c,2

14.57

0.14

d,3

18.67

0.31

d,4

23.27

0.25

d,5

21.57

0.22

a,1

2.87

0.30

b,1

5.87

0.22

d,2

10.57

0.25

d,3

14.57

0.22

d,4

1.3

T65.87

0.16

c,1

9.27

0.15

c,2

12.67

0.16

c,3

16.27

0.22

c,4

21.67

0.22

c,5

2.4

1.57

0.12

a,1

2.17

0.30

a,1

4.77

0.22

c,2

9.27

0.26

c,3

13.37

0.22

c,4

0.6

T74.17

0.14

b,1

7.67

0.15

b,2

10.87

0.18

b,3

14.57

0.20

b,4

18.67

0.22

b,5

2.1

1.17

0.12

a,1

1.87

0.25

a,1

3.17

0.25

b,2

6.27

0.28

b,3

8.97

0.28

b,4

0.7

T82.87

0.12

a,1

5.97

0.22

a,2

8.87

0.16

a,3

12.37

0.21

a,4

15.87

0.24

a,5

1.9

1.17

0.12

a,1

1.67

0.23

a,1

2.27

0.20

a,2

4.77

.24a

,3

6.57

0.21

a,4

0.5

LSD

0.9

1.1

0.9

0.8

0.7

0.6

0.5

0.7

0.9

0.7

Values

aremea

n7

SD,n

¼3;

LSD¼leastsign

ificantdifference

(pr

0.05

);CMC¼carbox

ymethy

lcellu

lose.

Values

within

trea

tmen

tsin

aco

lumnnot

sharingaco

mmon


letter

(a–g)

aresign

ificantly(p

r0.05

)different.

Values

within

storag

eperiodsin

arow

not

sharingaco

mmon


(1–5)

aresign

ificantly(p

r0.05

)different.

T1¼co

ntrol;T2

¼0.5%

w/v

CMC;T3

¼0.75

%w/v

CMC;T4

¼1.0%

w/v

CMC;T5

¼1.5kG

y;T6

¼0.5%

w/v

CMC,1.5

kGy;

T7¼0.75

%w/v

CMC,1.5

kGy;

T8¼1.0%

w/v

CMC,1.5

kGy.


3.4. Ascorbic acid content

Effect of CMC coating and gamma irradiation treatment onascorbic acid content of plum is shown in Table 3. The data revealsthat ascorbic acid content of fruits treated with irradiation aloneand in combination with CMC coating at 0.5–1.0% w/v is margin-ally (p40.05) lower compared to control and 0.5–1.0% w/v CMCcoated samples at first day of storage irrespective of storage con-dition. During storage, decrease in ascorbic acid was observed inall the treatment and the decrease was significantly (pr0.05)higher in fruits stored under ambient condition compared to thosestored under refrigerated condition. Statistically analysis of thedata indicated that for all the storage periods under both condi-tion, ascorbic acid content of control and 0.5% w/v CMC coatedsamples was marginally (p40.05) different with respect to eachother but, significantly (pr0.05) lower compared to other treat-ments. After 4 days of ambient storage, there was no significant(p40.05) difference in ascorbic acid content of fruits treated withCMC coating alone at 0.75 and 1.0% w/v, combination of CMCcoating (0.75, 1.0% w/v) and irradiation (1.5 kGy) and irradiationalone at 1.5 kGy or in combination with 0.5% w/v CMC coatingrespectively. This trend in ascorbic acid continued up to 16 days toambient storage. The percentage decrease in ascorbic acid contentafter 20 days of ambient storage was 92.2% in control, 85.4–90.6%in 0.5–1.0% w/v CMC coated fruits, 80.4% in 1.5 kGy irradiatedfruits and 69.6–77.2% in fruits treated with combination of CMCcoating and irradiation respectively. Under the refrigerated con-dition after 7 days of storage, there was no significant (p40.05)difference in ascorbic acid content of samples treated with irra-diation alone at 1.5 kGy and in combination with CMC coating at0.5–1.0% w/v. However, after 28 days of refrigerated storage, sig-nificant (pr0.05) differences in ascorbic acid existed among thetreatment and the levels were significantly (pr0.05) higher infruits treated with combination of CMC coating (1.0% w/v) andirradiation at 1.5 kGy. After 35 days of refrigerated storage, de-crease in ascorbic acid content was 90% in control, 73.6% in 1.5 kGyin irradiated sample and 58.7–68.1% in samples treated withcombination of CMC coating and irradiation respectively. Amongthe treatments, combination of CMC coating at 1.0% w/v and1.5 kGy irradiation was significantly (pr0.05) effective in pre-venting the decrease in ascorbic acid in plum fruits under bothstorage condition. Thus it can be inferred at main loss of ascorbicacid is because of storage rather than irradiation. The ascorbic acidloss during storage is known to be because of its antioxidantactivity especially under postharvest storage conditions (Daveyet al., 2000). Also, the lower ascorbic acid found just after irra-diation, in fruits treated with 1.5 kGy irradiation alone and incombination with coating seems to indicate that radiolysis couldaccelerate the conversion of ascorbic acid to dehydroascorbic acid(DHA). That is, ascorbic acid which is the reduced form and theone with a higher vitamin C activity can be rapidly and reversiblyoxidized to DHA, which is biologically active but to a less extent.Wong and Kitts (2001) suggested that the decrease in ascorbic acidin food during ionization can be attributed to two mechanisms:the first occurring by the direct oxidation of ascorbic acid throughthe action of OH radical generated by the water radiolysis in thefruits and the second by the oxidation of ascorbic acid, as it isconsumed during the treatment to protect other compoundsagainst the oxidative damage induced by the ionization.

3.5. Weight loss

Weight loss in fresh fruits and vegetables is mainly due to theloss of water caused by transpiration and respiration processes andis a major cause of quality deterioration in fresh horticultural cropsafter harvest. Effect of individual and combinatory treatments of

Table

5Effect

ofco

mbinationtrea

tmen

tof

CMCco

atingan

dga

mmairradiation

onov

erallacceptab

ility

ofplum

duringstorag

e.

Trea

tmen

tOve

rallac

ceptability

Ambientstorage

(day

s)Refrige

ratedstorage

(day

s)

48

1216

20LS

D7

1421

2835

LSD

T12.67

0.11

a,4

2.17

0.10

a,3

1.67

0.11

a,2

1.27

0.10

a,1

1.17

0.10

a,1

0.2

3.87

0.11

a,3

3.27

0.15

a,2

2.97

0.12

a,2

2.57

0.13

a,1

2.27

0.12

a,1

0.3

T22.67

0.13

a,5

2.17

0.11

a,4

1.77

0.12

a,3

1.47

0.12

a,2

1.17

0.11

a,1

0.2

3.87

0.11

a,4

3.47

0.16

a,3

3.17

0.15

a,2

2.67

0.13

a,1

2.57

0.12

b,1

0.1

T32.97

0.10

a,5

2.57

0.10

b,4

1.97

0.12

b,3

1.67

0.12

b,2

1.27

0.11

a,1

0.2

3.87

0.12

a,4

3.47

0.15

a,3

3.17

0.18

a,2

2.77

0.11

b,1

2.57

0.15

b,1

0.2

T43.47

0.13

b,5

3.17

0.10

c,4

2.87

0.13

c,3

2.47

0.13

c,2

1.97

0.12

b,1

0.1

3.97

0.10

a,4

3.87

0.13

b,4

3.57

0.16

b,3

3.17

0.14

c,2

2.87

0.12

c,1

0.2

T53.87

0.11

c,5

3.57

0.11

d,4

3.17

0.14

d,3

2.77

0.11

d,2

2.27

0.15

c,1

0.2

3.97

0.10

a,3

3.97

0.10

b,3

3.87

0.22

c,3

3.47

0.15

d,2

3.17

0.12

d,1

0.1

T63.87

0.12

c,5

3.57

0.10

d,4

3.27

0.13

d,3

2.97

0.12

d,2

2.57

0.12

d,1

0.1

3.97

0.10

a,3

3.97

0.10

b,3

3.87

0.12

c,3

3.67

0.15

e,2

3.47

0.14

e,1

0.1

T73.97

0.10

c4

3.87

0.11

e,4

3.47

0.14

e,3

3.17

0.10

e,2

2.87

0.12

e,1

0.2

3.97

0.10

a,3

3.97

0.10

b,3

3.97

0.10

c,3

3.87

0.12

f,2

3.67

0.15

f,1

0.1

T83.97

0.10

c,3

3.87

0.12

e,3

3.87

0.15

f,3

3.57

0.11

f,2

3.17

0.14

f,1

0.2

3.97

0.10

a,3

3.97

0.10

b,2

3.97

0.10

c,2

3.87

0.13

f,2

3.67

0.15

f,1

0.1

LSD

0.3

0.2

0.1

0.2

0.1

0.1

0.2

0.2

0.1

0.1

Values

aremea

n7

SD,n

¼3;

LSD¼leastsign

ificantdifference

(pr

0.05

);CMC¼carbox

ymethy

lcellu

lose.

Values

within

trea

tmen

tsin

aco

lumnnot

sharingaco

mmon


letter

(a–f)

aresign

ificantly(p

r0.05

)different.

Values

within

storag

eperiodsin

arow

not

sharingaco

mmon


(1–5)

aresign

ificantly(p

r0.05

)different.

T1¼co

ntrol;T2

¼0.5%

w/v

CMC;T3

¼0.75

%w/v

CMC;T4

¼1.0%

w/v

CMC;T5

¼1.5kG

y;T6

¼0.5%

w/v

CMC,1.5

kGy.

T7¼0.75

%w/v

CMC,1.5

kGy;

T8¼1.0%

w/v

CMC,1.5

kGy.


CMC coating and gamma irradiation on weight loss of plum fruit isshown in Table 4. It is seen from the Table 4 that weight lossincreased during storage in all the treatments under both thestorage conditions and was significantly (pr0.05) higher underambient conditions compared to refrigerated condition. Statisticalanalysis reveals that under refrigerated conditions, increase inweight loss was almost static up to 14 days and beyond that aprogressive increase in weight loss was recorded. Data analysisindicated that weight loss of control and 0.5% w/v CMC coatedfruits was marginally (p40.05) different with respect to one an-other and significantly (pr0.05) higher than other treatmentsthroughout the storage under both the storage conditions. It is alsoclear from the Table 4 that combined treatments of 1.0% w/v CMCcoating and 1.5 kGy irradiation significantly (pr0.05) reduced theweight loss of plums under both the conditions. The reduction inweight loss in plum fruits treated with combination of CMCcoating and irradiation is due to the delaying effects of the treat-ments on the natural physiological processes like respiration andtranspiration (Hussain et al., 2012). Further coatings are clearlyeffective in conferring a physical barrier to moisture loss, andtherefore retarding dehydration and fruit shriveling (Almenaret al., 2006).

3.6. Overall acceptability (OAA)

Overall acceptability based on color, texture and taste of theplum fruits treated with CMC coating and irradiation is shown inTable 5. Data analysis indicated that after 4 days of ambientstorage, overall acceptability values of control, 0.5% and 0.75% w/vCMC coated fruits were marginally different (p40.05) with re-spect to each other and significantly (pr0.05) lower compared toother treatments. The OAA values of samples treated with irra-diation alone or in combination with CMC coating (0.5–1.0% w/v)were also marginally different with respect to each other after4 days of ambient storage. Under refrigerated conditions, therewas no change in overall acceptability values in samples treatedeither with individual treatments of 1.0% w/v CMC, 1.5 kGy irra-diation or combination of CMC coating (0.5–1.0% w/v) and irra-diation (1.5 kGy) up to 7, 14 and 21 days when compared valuesat harvest time. With further advancement in storage, overallacceptability values decreased significantly (pr0.05) in all thetreatments irrespective of storage condition. Based on limit ofacceptability, it can be inferred from the data that control, 0.5 and0.75% w/v CMC coated samples were unacceptable after 8 and 12days of ambient storage respectively. Similarly, the samplestreated with 1.0% w/v CMC and irradiation alone at 1.5 kGy wererated unacceptable after 16 and 20 days of ambient storagerespectively. However, samples treated with combination of CMC(0.5–1.0% w/v) and irradiation were rated acceptable even after 20days of ambient storage. Under refrigerated condition, controlsamples and those treated with CMC at 0.5 and 0.75% w/v wererated unacceptable after 28 and 35 days of storage respectively. Allother samples treated with CMC and irradiation either alone or incombination were acceptable up to 35 days of storage. Among thetreatments, combination of 1.0% w/v CMC and 1.5 kGy irradiationresulted in significant effect in retention of OAA of plum fruitsunder both the storage condition compared to other treatments.The fast decrease in overall acceptability of control and CMCcoated samples (0.5 and 0.75% w/v) is related to the decrease intexture, color and loss of volatile as perceived by the panelistsbecause of rapid ripening and senescence and fungal decay. Thesynergistic effect of combinatory treatment of coating and irra-diation on inhibition of fungal growth and retention of texture andcolor proved the significantly beneficial effect (pr0.05) in main-taining higher overall acceptability of treated plums comparedwith control samples during storage (Hussain et al., 2010).

Table

6Effect

ofco

mbinationtrea

tmen

tof

CMCco

atingan

dga

mmairradiation

onmicrobial

load

ofplum

duringstorag

e.

Trea

tmen

tMicro

bialload

(yea

stan

dmold

count,logcfu/g

sample)

Ambientstor

age(day

s)Refrige

ratedstor

age(day

s)

04

812

1620

LSD

07

1421

2835

LSD

T13.37

0.1a

,1

3.87

0.1b

,2

4.27

0.1b

,3

4.47

0.1c

,3

4.67

0.2d

,4

5.37

0.2e

,5

0.2

3.37

0.1a

,1

3.57

0.3b

,1

3.97

0.3b

,2

4.27

0.3b

,3

4.57

0.1c

,4

4.87

0.1d

,5

0.2

T23.37

0.1a

,1

3.87

0.2b

,2

4.17

0.2b

,3

4.27

0.1b

,3

4.57

0.2d

,4

4.97

0.2d

,5

0.2

3.37

0.1a

,1

3.67

0.2b

,1

3.87

0.3

b,2

4.27

0.3b

,3

4.47

0.2c

,3

4.77

0.2

d,4

0.3

T33.07

0.0a

,1

3.67

0.1a

,2

3.97

0.2a

,2

4.17

0.3b

,3

4.37

0.2c

,3

4.77

0.3c

,4

0.3

3.07

0.0a

,1

3.17

0.3a

,1

3.57

0.2a

,2

3.87

0.1a

,2

4.17

0.2b

,3

4.57

0.2c

,4

0.3

T4ND

3.37

0.2d

,1

3.67

0.2a

,2

3.97

0.3b

,3

4.27

0.3c

,4

4.57

0.2c

,5

0.2

ND

ND

3.37

0.2a

,1

3.67

0.3a

,1

3.97

0.1b

,2

4.17

0.1c

,2

0.3

T5ND

ND

ND

3.47

0.3a

,1

3.77

0.2b

,2

4.17

0.2b

,3

0.2

ND

ND

ND

ND

3.37

0.3a

,1

3.57

0.1b

,1

0.3

T6ND

ND

ND

3.47

0.2a

,1

3.67

0.2b

,1

4.17

0.1b

,2

0.2

ND

ND

ND

ND

3.07

0.1a

,1

3.27

0.1a

,1

0.3

T7ND

ND

ND

ND

3.37

0.1a

,1

3.57

0.2a

,1

0.2

ND

ND

ND

ND

ND

3.37

0.1a

,4

-T8

ND

ND

ND

ND

3.17

0.1a

,1

3.37

0.2a

,1

0.2

ND

ND

ND

ND

ND

3.07

0.1a

,3

-LS

D0.3

0.3

0.3

0.3

0.2

0.3

0.3

0.2

0.3

0.3

0.3

0.4

Values

aremea

n7

SD,n

¼3;

LSD¼leastsign

ificantdifference

(pr

0.05

);CMC¼carbox

ymethy

lcellu

lose;ND¼not

detected.

Values

within

trea

tmen

tsin

aco

lumnnot

sharingaco

mmon


letter

(a–e)

aresign

ificantly(p

r0.05

)different.

Values

within

storag

eperiodsin

arow

not

sharingaco

mmon


(1–5)

aresign

ificantly(p

r0.05

)different.

T1¼co

ntrol;T2

¼0.5%

w/v

CMC;T3

¼0.75

%w/v

CMC;T4

¼1.0%

w/v

CMC;T5

¼1.5kG

y;T6

¼0.5%

w/v

CMC,1.5

kGy.

T7¼0.75

%w/v

CMC,1.5

kGy;

T8¼1.0%

w/v

CMC,1.5

kGy.


3.7. Microbial load and decay percentage

Effect of individual and combination treatments of CMC coatingand radiation processing on microbial load as yeast and moldcount and decay percentage of plums during ambient, refrigeratedand post-refrigerated storage at 2572 °C, RH 80% is shown inTables 6 and 7 respectively. Data pertaining to microbial load re-vealed that irradiation treatment alone and in combination withCMC coating decreased significantly (pr0.05) the yeast and moldcount under both storage conditions. In irradiated samples(1.5 kGy) alone and in combination with CMC coating at 0.5–1.0%w/v, no microbial load was detected up to 8 and 12 days of am-bient storage. Data analysis indicated that gamma irradiationtreatment of plums at 1.5 kGy alone and in combination with 0.5%,0.75% and 1.0% w/v CMC resulted in 1.2, 1.8 and 2.0 log reduction inmicrobial load after 20 days of ambient storage respectively whencompared with control. Treatment of CMC coating at 0.5%, 0.75%and 1.0% w/v gave 0.4, 0.6 and 0.8 log reduction in yeast and moldcount of plums after 20 days of ambient storage. Under re-frigerated conditions, treatments of CMC coating at 1.0% w/v,1.5 kGy irradiation and combination of 0.5% w/v CMC and 1.5 kGyirradiation inhibited the occurrence of yeast and mold growth upto 7 and 21 days of storage. Combination of CMC coating (0.75, 1.0%w/v) and 1.5 kGy irradiation proved significant in inhibiting themicrobial growth up to 28 days of storage. Data on decay per-centage indicated that under ambient condition; control and 0.5%w/v CMC coated samples started decaying after 9 days and werealmost fully decayed after 23 days of storage. Fruits treated withCMC coating at 0.75 and 1.0% w/v started decaying after 11 and 13days of ambient storage. Irradiation alone and in combination withCMC coating proved significant (pr0.05) in delaying the onset ofdecay in plum fruits stored under ambient conditions. In fruitstreated with irradiation alone at 1.5 kGy and in combination withCMC at 0.5, 0.75 and 1.0% w/v, no decay was recorded up to 17, 19and 21 days of ambient storage. Under refrigerated conditionsafter 45 days of storage, no decay was recorded in fruits treatedwith CMC coating (0.75, 1.0% w/v), 1.5 kGy irradiation and com-bination of CMC coating (0.5–1.0% w/v) and 1.5 kGy irradiationcompared to control and 0.5% w/v CMC coated fruits which weredecayed to the extent of 19.5% and 12.5%. After 45 days of re-frigeration, fruits were taken out and kept under ambient condi-tions (2572 °C, RH 80%) to monitor decay. Control and 0.5% w/vCMC coated fruits were almost fully decayed after 7 and 8 days ofstorage. In fruits treated with 0.75% and 1.0% w/v CMC coating, nodecay was recorded up to 2 and 5 days of additional ambientstorage following 45 days of refrigeration. Gamma irradiationalone at 1.5 kGy and in combination with CMC coating (0.5 and0.75% w/v) delayed the onset of decay in plum fruits up to 8 daysof additional ambient storage following 45 days of refrigeration.Among the treatments, combination of 1.0% w/v CMC coating and1.5 kGy irradiation was effective in delaying the decay of plumfruits up to 11 days of storage at 2572 °C, RH 80% following 45days of refrigerated storage. Thus, the synergistic effect of gammairradiation and CMC coating in delaying physiological processesand microbial proliferation responsible for decay has resulted inextending the shelf life of plum fruits under ambient, refrigeratedand additional ambient storage following refrigeration (Hussainet al., 2010).

4. Conclusion

The investigation showed that CMC coating alone at levels0.5 and 0.75% w/v was not found effective with respect to shelf lifeextension of plum fruit. CMC coating at 1.0% w/v gave 5 days ex-tension in shelf life of plum compared to 8 days by irradiation at

Table 7Effect of combination treatment of CMC coating and gamma irradiation on decay of plum during ambient, refrigerated and post-refrigerated storage at 2572 °C, RH 80%.

Treatment Decay (%)

(a) Ambient storage (days)

7 9 11 13 15 17 19 21 23 25 27 30

T1 ND 14.770.21b 23.170.24c 31.570.32d, 46.370.22d 65.170.20d 73.370.18e 85.270.21f 91.270.21e FD – –

T2 ND 9.770.22a 15.170.20b 23.370.26c 31.370.24c 45.170.18c 58.370.16d 71.270.23e 88.270.21e FD – –

T3 ND ND 7.670.14a 14.870.24b 23.870.22b 32.570.26b 43.870.20c 54.370.16d 69.570.25d 83.370.31e FD –

T4 ND ND ND 5.570.20a 10.170.24a 18.370.20a 25.870.18b 36.170.13c 46.370.26c 59.870.33d 72.270.21d 84.270.21d

T5 ND ND ND ND ND ND 4.470.25a 9.870.22b 14.270.16b 21.370.12c 29.870.22c 37.270.34c

T6 ND ND ND ND ND ND 4.370.20a 7.370.15a 12.570.14b 18.770.20b 25.270.36b 34.270.21b

T7 ND ND ND ND ND ND ND 4.370.12a 9.770.22a 15.270.21b 22.270.21b 31.270.21b

T8 ND ND ND ND ND ND ND ND 6.670.12a 10.570.20a 16.270.21a 22.470.21a

LSD 3.5 4.5 3.6 5.2 6.5 5.1 3.2 4.2 3.5 3.5 4.30.5

(b) Refrigerated and post-refrigerated storage at 2572 0C, RH 80%

Treatment 45 DOR 1 2 3 4 5 6 7 8 9 11 13

T1 19.570.21b 23.570.24b 31.370.32b 43.870.22c 56.370.20c 75.170.18c 81.370.21d FD – – – –

T2- 12.570.21a 17.570.21a 25.570.21a 36.370.26b 47.570.24b 64.370.18b 73.270.16c 88.770.23c FD – – –

T3 ND ND ND 4.270.20a 12.270.16a 25.270.28a 34.770.31b 49.570.17b 66.270.18b 79.270.18c 91.270.18c FDT4 ND ND ND ND ND ND 6.270.18a 13.370.13a 22.570.26a 33.770.33b 47.570.21b 63.270.18c

T5 ND ND ND ND ND ND ND ND ND 5.570.12a 12.570.22a 21.270.18b

T6 ND ND ND ND ND ND ND ND ND 6.270.14 a 11.370.20 a 20.570.36b

T7 ND ND ND ND ND ND ND ND ND 6.270.22a 10.270.18a 18.270.18b

T8 ND ND ND ND ND ND ND ND ND ND ND 6.270.12a

LSD 3.5 3.5 4.3 5.4 5.1 5.5 5.8 5.5 6.1 3.1 2.5 3.5

Values are mean7SD, n¼3; LSD¼ least significant difference (pr0.05); CMC¼carboxymethyl cellulose; ND¼no decay; FD¼ full decay.DOR¼days of refrigeration.Values within treatments in a column not sharing a common superscript lowercase letter (a–g) are significantly (pr0.05) different.Values within storage periods in a row not sharing a common superscript numerical (1– 6) are significantly (pr0.05) different.T1¼control; T2¼0.5% w/v CMC; T3¼0.75% w/v CMC; T4¼1.0% w/v CMC; T5¼1.5 kGy; T6¼0.5% w/v CMC, 1.5 kGy.T7¼0.75% w/v CMC, 1.5 kGy; T8¼1.0% w/v CMC, 1.5 kGy.

P.R.H

ussainet

al./Radiation

Physicsand

Chemistry

107(2015)

136–148

147


1.5 kGy following 45 days of refrigeration. All combinatory treat-ments of CMC coating and irradiation proved beneficial in main-taining the storage quality as well as delaying the decaying ofplum during post-refrigerated storage at 2572 °C, RH 80%. How-ever, combination of CMC at 1.0% w/v and 1.5 kGy irradiation wasfound significantly (pr0.05) superior to all other treatments. Theabove combinatory treatment besides maintaining storage qualityresulted in extension of 11 days in shelf life of plum during post-refrigerated storage at 2572 °C, RH 80% following 45 days of re-frigeration. Irradiation alone at 1.5 kGy and in combination with1.0% w/v CMC coating resulted in 2.0 and 1.8 log reduction in yeastand mold count of plum fruits after 20 and 35 days of ambient andrefrigerated storage, thereby ensuring consumer safety. Therefore,combinatory treatment of coating (1.0% w/v CMC) and irradiation(1.5 kGy) can help to greater extent in facilitating the marketing ofthe fruit to distance markets other than local markets, therebybenefiting the growers.

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Retention of storage quality and post-refrigeration shelf-life extension of plum (Prunus domestica L.) cv. Santa Rosa using combination of carboxy methyl cellulose (CMC) coating and

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