"Effect of storage on the physico-chemical properties of canned and dehydrated okra* Bharti, Shelke AR , Ranote PSAbstract The study was carried out to check the effect of processing and storage on the physico- chemical composition and quality of fresh, canned and dehydrated okra fruits. Themoisture, pH,TSS, ascorbic acid, protein, pectin, crude fibre and chlorophyll content of fresh okra fruits was 89.65o %, 6.79, 16.00 Brix, 21.82 mg/100g, 1.99 %, 0.30 %, 3.75 % and 75.97 mg/100g, respectively.Moisture, pH, TSS, ascorbic acid, pectin, crude fibre and chlorophyll content of canned okradecreased by 2.08, 1.62, 38.88, 47.50, 21.25, 52.06 and 53.65 %, while protein increased by 29.79 %during 6 months of storage at ambient conditions. The moisture content and pH of dehydrated okraincreased by 3.07 and 0.90 %, respectively whereas TSS, ascorbic acid, protein, pectin, crude fibreand chlorophyll content decreased by 39.58, 56.44, 3.18, 28.62, 19.58 and 26.38 %, respectivelyduring 6 months of storage packed in HDPE bags stored under ambient conditions.Keywords Okra · Canning · Dehydration · Storage · Physico-chemical propertiesIndia has favourable agro-climatic conditions for the cultivation of large number ofhorticultural crops and is the second largest producer of vegetables after China. Okra belongs to thefamily Malvaceae, genus Abelmoschus and species esculentus. Okra is known by many local names indifferent parts of the world. It is quite popular in India because of easy cultivation, dependable yieldand adaptability to varying conditions. Even within India, different names have been given in differentregional languages (Chauhan, 1972). Okra has a vast potential as one of the foreign exchange earnercrop and accounts for about 60 per cent of the export of fresh vegetables excluding potato, onion,garlic etc. (Anon 2003). Okra can be cooked in variety of ways. It can be fried in butter or butter oiland cooked with necessary ingredients. It can be boiled and served as salad or cut into pieces andserved with soup. In some countries, including certain parts of India, the pods are used for thickeningof curried vegetables. A typical example is that of sambre, a vegetable preparation customarily used bya vast segment of rice-eating inhabitants of Southern India. In some places, the plants are soaked inwater and the resulting solution is used as a clarifier in the manufacture of jaggery. Its ripe seeds areroasted, ground and used as a substitute for coffee in Turkey (Mehta 1959). The total okra productionin India during the year 2009-2010 was 4803.3 thousand tonnes from area of 452.5 thousand hectares.Out of this, Punjab produced 20 thousand tonnes from area of 2.6 thousand hectares (Anon 2009). A major goal of food processing is to convert perishable commodities into stable products thatcan be stored for extended periods thereby reducing losses and making them available at the times ofshortage and out of season and at places far away from the site of production. In Punjab, during thepeak production season in May, there is glut in the local market and the prices crash beyond expectation, causing financial losses to the growers. The shelf life of okra fruit is dependent onambient temperature. In loosely filled baskets, it can be stored for 2 to 3 days at the most. Keeping inview low prices and low shelf life, processing technology should be developed for preservation andincreasing shelf life. Processing can change foods into new or more usable forms and make them moreconvenient to prepare. Several process technologies have been employed on industrial scale topreserve fruits and vegetables, the major ones being canning, freezing and drying.As a matter of fact, frozen food industry in the Punjab state without an assured power supplyseems a gamble, apart from the high costs involved. However, canning and dehydration in tropicalcountries offer promise. Drying is the oldest, cheapest and most widely used method of preservation.The removal of moisture prevents the growth and reproduction of micro-organisms causing decay. Itbrings about substantial reduction in weight and volume. Minimizing packing, storage andtransportation costs and enables storability of the product under ambient temperatures, featuresespecially important for developing countries and in military feeding and space food formulations.Besides, drying has some other benefits like increased shelf life, less energy requirement than what isneeded in freezing.Materials and methodsProcurement of raw material: Okra fruits were procured from the local market of Ludhiana in the midof January (2011) and were immediately processed at Pilot Plant of Department of Food Science andTechnology, Punjab Agricultural University, Ludhiana. The lacquered A1 size cans were used for thecanning of the okra and HDPE (High Density Polyethylene) bags having the size 20 cm x 15 cm andthickness 200 gauge were used to store the dehydrated okra.Physical characteristics of fresh okra: Fresh okra fruits were washed thoroughly under running tapwater, weighed and the damaged/infected parts were trimmed out and percent losses were noted. Okrawere cut into suitable sizes, blanched in boiling water for 3 min and percent losses of blanching wererecorded.Canning of okra: The okra after blanching was dipped in 1.5 per cent brine solution for 10 min.Blanched 230g okra were filled in previously sterilized cans. Hot brine solution of 2 per centconcentration was added into the cans leaving headspace 0.32-0.47 cm. Filled cans covered with looselids were exhausted at 90-100 °C for 10 min. Cans were immediately sealed and processed in boilingwater for 20 min., cooled and stored at ambient condition.Drying of okra: Blanched okra was dipped in 0.2 per cent KMS solution for 10 min and later loadedin trays at the rate of 1.25 kg/sq m. The trays were placed in cross-flow hot air (Frederick-Herbert)o cabinet drier which was preheated to a temperature of 60 C and a constant temperature of 65 ± 2 °Cwas maintained till the drying completed. Weight of the drying material was noted at one-hourinterval till drying process completed. The dehydrated okra were packed in HDPE bags and stored atambient condition. physico-chemical analysis: Processed okra were analyzed at 0, 1, 2, 3, 4, 5 and 6 months interval forvarious physico-chemical changes occurring during storage like total soluble solids, moisture,ascorbic acid, pH, protein, crude fibre, pectin and chlorophyll using standard methods (AOAC 2000,Ranganna 1994).Sensory quality: Sensory quality of stored okra products was evaluated on the basis of sensoryattributes (appearance, colour, texture and flavor) by a panel of semitrained judges (Larmond 1970).Statistical analysis: Experiments were carried out in triplicate and data was analysed with the help offactorial designs in CRD (Singh et al. 1998).Results and discussionPhysico-chemical composition of fresh okra fruits: The physico-chemical composition of fresh okrao fruits is presented in Table 1. Total soluble solids (%), Moisture ( Brix), Ascorbic acid (mg/100gm),pH, Protein (%), Crude fiber (%), Pectin (%) and Chlorophyll (mg/100gm) content of fresh okra fruitswas 16.00, 89.65, 21.82, 6.79,1.99, 3.75, 0.30 and 75.97, respectively.Preparation losses and yield of the product: Okra fruits were thoroughly washed under running tapwater. Defective, infected fruits were manually sorted out and spoiled parts of the okra fruits weretrimmed out with the help of stainless steel knife. Head and stem side portions were removed andfruits were cut into disc shape of 1.5 cm thickness. The rejected portion was recorded as per centtrimming losses which were found to be 16.41 per cent (Table 2). After the trimming and cutting, theokra fruits were blanched in boiling water for 3 min. Blanched okra fruits were weighed andblanching losses were recorded as 4.23 per cent (Table 2). The weight loss of the material duringdehydration wasrecorded at 1 hr interval till complete dehydration was achieved. Data so recordedhas been presented in drying curve plotted as drying time (hrs) vs per cent moisture content (Fig. 1)whereas dehydration ratio of okra refers to the yield per cent of the dried okra from fresh fruits whichwas recorded as 9.33 (Table 2). 100 90 80 70 60 50 40 30 20 10 0 0 1 2 3 4 5 6 7 8 9 10 11 Drying time (hrs.) o Fig.2: Drying curve of okra fruits at 65 ± 2 C temperatureStorage studies: Canned and dehydrated okra products were stored at ambient conditions for 6 monthsand analysed for physico-chemical composition to assess the effect of storage on quality of products.Total soluble solids: The effect of storage on total soluble solids as investigated during storage periodof 6 months has been presented in Table 3. Total soluble solids decreased in both, whether canned oro dehydrated okra. Total soluble solids decreased from 3.60 to 2.20 and 48.00 to 29.00 Brix accounting38.88 and 39.58 per cent decrease in canned and dehydrated okra, respectively during 6 months ofstorage. The decrease in TSS values both in canned and dehydrated okra was faster during first onemonth of storage whereas it decreased slowly with the progression of storage period. Decrease in TSSvalue of canned okra might be due to the leaching of soluble solids from okra sample to surroundingliquid whereas in case of dehydrated okra, absorption of moisture during storage could be the reasonfor decreased in total soluble solid values. Similar results were reported by Sra et al. (2011) for driedcarrot slices when packed and stored in Aluminium Foil Laminate and High Density Polyethylenebags. The effect of process and storage was found statistically significant (P<0.05) on the total solublesolids content of the product.Moisture: The data regarding moisture content of canned and dehydrated okra during storage periodof 6 months has been presented in Table 3. During storage period, moisture content decreased incanned okra where as increased in dehydrated okra. Moisture content decreased from 96.94 to 94.90per cent accounting 2.08 per cent decrease in canned okra whereas increased from 8.48 to 8.75 percent accounting 3.07 per cent increase in dehydrated okra during 6 months of storage. Decrease inmoisture content in canned okra during storage might be due to the maintenance of moistureequilibrium with surrounding liquid whereas increased moisture content in dehydrated okra might bedue to the hygroscopic nature of product that might have absorbed the atmospheric moisture with theMoisture content (%)progress of storage period. The observations were in the conformity with the findings reported by Daset al. (1993a) for the canned peas and Adom et al. (1996) in dried okra powder. The effect of processand storage was found statistically significant (P<0.05) on the moisture content of the products.Ascorbic acid: Losses of ascorbic acid in canned and dehydrated okra was due to high temperatureinvolved in the processing and further losses during storage was due to the effect of light, metallicions and prevailing high room temperature conditions. The residual ascorbic acid content in thecanned and dehydrated okra at different storage intervals has been listed in Table 3. Considerableamount of ascorbic acid seemed to have lost during canning and dehydration. Ascorbic acid decreasedfrom 9.01 to 4.73 mg/100g in canned okra representing 47.50 per cent loss during 6 months ofstorage. Whereas in case of dehydrated okra, the loss of ascorbic acid from the initial value of 20.40mg/100g was 9.06 mg/100g after termination of storage period which represented 56.4 per cent totalloss. Loss of ascorbic acid in the processed stored products have been reported by many otherworkers. Similar pattern of ascorbic acid losses as recorded in present study were reported by Howardet al. (1999) in canned carrot and Sra et al. (2011) in dried carrot slices packed and stored inAluminium Foil Laminate and High Density Polyethylene bags. The effect of process and storage wasfound statistically significant (P<0.05) on the ascorbic acid content of the products.pH: The data regarding pH have been presented in Table 3. Minor decrease in the pH values in cannedokra were recorded. With the initial pH value of 6.78 it reduced to 6.67 after the completion of storageperiod of 6 months. The results were in the agreement of the observations reported by Kaur and Bains(1992) in canned okra. Similarly slight increase in pH values of dehydrated okra were recorded as6.65 initial pH to 6.71 pH value depicting 0.90 per cent increase in dehydrated okra during 6 monthsof storage. Similar observations were reported by Randhawa and Ranote (2004) in stored mushroompowder. The statistical analysis showed that storage had non-significant effect while process hadsignificant effect (P<0.05) on pH values of the products.Protein: Data regarding protein and storage behaviour of canned and dehydrated okra has been givenin Table 3. Slight increase in protein content of canned okra was noticed during the storage period of6 months from the initial value of 0.94 per cent, increased to 1.22 per cent with a mean value of 1.09per cent. Minor increase in protein content of canned okra might be due to the decrease in moistureand hence concentration of the constituents in the canned okra fruits. Similar results in canned peas ofvariety Harabona B had been reported by Das et al. (1993a). Protein content in dehydrated okradecreased from 18.86 to 18.26 per cent after storage period of 6 months. Decreased protein content ofdehydrated okra might be due to the results of protein breakdown and participation of amino acids ofproteins into non-enzymatic reactions. The results are in conformity with the one reported byRandhawa and Ranote (2004) in stored mushroom powder. Data when analyzed statistically, theeffect of process and storage was found significant (P<0.05) on the protein content of the products.Crude fiber: Results showing the effect of storage on crude fiber content of canned and dehydratedokra have been presented in Table 3. Crude fiber decreased in both, whether canned or dehydrated okra but rate of decrease of crude fiber in canned okra was higher than dehydrated okra. The crudefiber content at initial stage of canned okra was 3.40 per cent and with the progression of storageperiod, it decreased to 1.63 per cent representing 52.06 per cent decrease after 6 months of storage.Similarly, crude fiber content of dehydrated okra decreased but at slower pace. Initial value ofcrude fiber for dehydrated okra was 50.55 per cent and it decreased to 40.65 per cent after 6 monthsof storage. Decrease in crude fiber content of canned and dehydrated okra might be due toconversion of crude fiber like cellulose into carbohydrates. Similar decreasing trend of crude fiberduring storage period been reported by Das et al. (1993a) in canned peas while Randhawa andRanote (2004) in stored mushroom powder. The factors like process and storage period had thesignificant effect (P<0.05) on crude fiber content of products when analysed statistically.Pectin: Behaviour of the pectin content in canned and dehydrated okra during storage has beenreported in Table 3. In general, pectin decreased in both canned and dehydrated okra to the tuneof 21.25 to 44.00 per cent, respectively during 6 months of storage. Initial value of pectin contentin canned okra was 0.080 per cent while it was 2.97 per cent for dehydrated okra and decreased to0.063 per cent in canned and 2.12 per cent in dehydrated okra after 6 months of storage. Thedecreased pectin content both in canned and dehydrated okra might be due to the hydrolysis as aconsequence of conversion of water soluble pectin into oxalate soluble pectin. Dried carrot slicesexhibited same type of decreasing behaviour in pectin content but to lesser extent as reported bySra et al. (2011). Statistically significant (P<0.05) effect of process and storage period was foundon pectin content of the products.Chlorophyll: Decreasing trend of chlorophyll content with the storage was noticed in canned anddehydrated okra fruits (Table 3). Chlorophyll content seemed to have decreased considerably incanned and dehydrated okra with mean values of 43.36 and 144.66 mg/100g, respectively during 6months of storage. Initial and final chlorophyll content for canned okra was 62.57 and 29.00 mg/100gwhile 166.75 and 122.76 mg/100gm chlorophyll values were recorded in dehydrated okra. Per centdecrease in chlorophyll content was 53.65 in canned okra and 26.38 in dehydrated okra after 6 monthsof storage. The chlorophyll content in the product decreased with storage probably because ofconversion of chlorophyll pigment into pheophytin pigment. Similar decreasing trend in chlorophyllcontent during storage period had been reported by Kaur and Bains (1992) in canned okra and Das etal. (1993b) in dehydrated peas. The effect of process and storage was found statistically significant(P<0.05) on chlorophyll content of products.Rehydration ratio: Rehydration ratio refers to the gain in weight of the dried material afterreconstitution with water. The effect of storage on rehydration ratio of dehydrated okra as investigatedduring storage period of 6 months has been presented in Table 3. Rehydration ratio decreased from5.89 to 5.47 with mean value of 5.68 during 6 months of storage. The decrease in rehydration ratiomight be due to decrease water holding capacity of the product. Similar observations were reported by Sra et al. (2011) in dried carrot slices packaged in Aluminium Foil Laminate and High DensityPolyethylene bags and Das et al. (1993b) in dehydrated peas.Sensory evaluationThe results of sensory evaluation of canned and dehydrated okra stored at ambient temperature andevaluated at 2 months intervals have been presented in Table 4.Appearance: Appearance scores for canned okra decreased from 7.83 to 6.83 with mean value of 7.29while for dehydrated okra, appearance scores decreased from 8.50 to 7.67 with mean value of 8.00,during 6 months of storage. Similar observation for appearance values have been reported by Sra et al.(2011) in cooked curried carrots prepared from dried carrot slices. The effect of process and storagewas found statistically significant (P<0.05) on the appearance of the products.Colour: The colour scores secured by dehydrated okra was more than canned okra at initial stage ofstorage (8.67 and 8.50). At the end of storage studies, the values were 7.00 for canned okra and 8.00for dehydrated okra (Table 4). Similar results had been reported in colour scores of stored mushroompowder by Randhawa and Ranote (2004) and in dried tomato halves packed in Aluminium FoilLaminate pouches by Madan et al. (2008). Data upon analyzing statistically, was found to havesignificant effect (P<0.05) of process and storage on the colour of the products.Texture: Dehydrated okra secured more texture scores than canned okra. The initial and final texturescore values were 8.17 and 6.67 for canned okra with mean value of 7.38 whereas 8.67 and 7.83 withmean value of 8.25 for dehydrated okra. Similar observations had been reported for texture scores ofcooked curried carrots prepared from dried carrot slices by Sra et al. (2011) and in mushroom powderby Randhawa and Ranote (2004). Process and storage had significant effect (P<0.05) on the texture ofthe products.Flavour: Flavour scores decreased from 8.33 to 7.00 and 8.33 to 7.83 for canned and dehydrated okrafruits, respectively during 6 months of storage. There was loss in flavour in stored product. Similartrend for flavour scores had been reported by Randhawa and Ranote (2004) in stored mushroompowder and Sra et al. (2011) in cooked curried carrots prepared from dried carrot slices. Statisticalanalysis showed that storage had non-significant effect while process had significant effect (P<0.05)on the flavour of the products.Overall acceptability: Maximum sensory scores were obtained by dehydrated okra followed bycanned okra immediately after preparation of product. This showed the significant effect of process onoverall acceptability of the product. Overall acceptability scores for canned and dehydrated okra fruitsdecreased from 8.21 to 6.87 and 8.54 to 7.83, respectively during 6 months of storage. Decrease in allsensory parameters were reported by Sra et al. (2011) in cooked curried carrots prepared from driedcarrot slices and Madan et al. (2008) in soup prepared from dried tomato halves packed in AluminiumFoil Laminate pouches. Statistically, overall acceptability of the okra products was significantly(P<0.05) effected by process and storage. ConclusionBoth the canned and dehydrated okra fruits were found better. The results showed that the process i.e.canning and dehydration largely affects the physico-chemical properties of okra fruits while storagehad the slight effect on the physico-chemical properties of okra. The values of the physico-chemicalparameters for dehydrated okra was higher ( except moisture content) with more overall acceptabilitythan the canned okra after the 6 months of storage. The okra can be successfully stored at ambienttemperature up to the 6 months by the canning and dehydration process.References:Adom KK, Dzogbefia VP, Ellis WO, Simpsor BK (1996) Solar drying of okra-effects of selectedpackage materials on storage stability. Food Res Int 29:589-593Anon (2003) Indian Agriculture. Pp. 201, 271. Published by Indian Economic Data Research Centre.Anon (2009) www.indiastat.comAOAC (2000) Official methods of Analysis. Association of Official Analytical Chemists,th Washington, DC, 14 edn.rd Chauhan DVS (1972) Vegetable production in India. 3 ed. Ram Prasad and Sons (Agra)Das N, Saini SPS, Bains GS (1993a) Effect of variety and maturity on canning characteristics of peas.Ind Food Packer 47(1):5-10Das N, Saini SPS,Bains GS (1993b) Effect of variety and maturity on quality and dehydrated peas.Ind Food Packer 47(3):17-24Howard LA, Wong AD, Perry AK, Klein B P (1999) Beta carotene and ascorbic acid retention infresh and processed vegetables. J Food Sci 64(5):929-936Kaur B, Bains GS (1992) Comparative studies on ready-to-serve canned okra in brine and tomatojuice. Ind Food Packer 46(3):21-26Larmond E (1970) Methods for sensory evaluation of food. Canada Department of Agriculture Pubn1284Mehta YR (1959) Vegetables growing in Uttar Pradesh. Bureau of Agric Inf, U.P., LucknowRandhawa GK,Ranote PS (2004) Storage stability of processed Oyster Mushroom (Pleurotus spp)into soup powder. J Food Sci Technol 41(5):525-529 nd Ranganna S (1994) Handbook of analysis and quality control for fruit and vegetable products (2edn) Tata Mc Graw-Hill Publishing Co. Ltd., New DelhiSingh S, Bansal ML, Singh TP, Kumar R (1998) Statistical methods for research workers. KalyaniPublishers, New DelhiSra SK, Sandhu KS, Ahluwalia P (2011) Effect of processing parameters on physico-chemical andculinary quality of dried carrot slices. J Food Sci Technol 48(2):159-166Table 1. Physicochemical composition of fresh okra fruitsParameters Valueso TSS ( Brix) 16.00pH 6.79Ascorbic acid (mg/100g) 21.82Moisture (%) 89.65Protein (%) 1.99Pectin (%) 0.30Crude fiber (%) 3.75Chlorophyll (mg/100g) 75.97Values are mean of 3 replicationsTable 2. Preparation losses and yield of the productCharacters Quantity Percent lossesTotal weight of fruits 1 kg -Trimming losses 164.1 g 16.41Blanching losses 42.3 g 4.23Dehydration ratio 9.33 -Values are mean of 3 replications Table 4. Effect of storage on the sensory quality of okra productsSensory Products Storage period (months) CD (P<0.05) CD (P<0.05) CD (P<0.05)parameter for Process for Storage for Process X0 2 4 6StorageAppearance Canned 7.83 7.33 7.17 6.83 0.30 0.43 NSDehydrated 8.50 8.00 7.83 7.67Colour Canned 8.50 7.83 7.50 7.00 0.26 0.37 NSDehydrated 8.67 8.50 8.17 8.00Texture Canned 8.17 7.67 7.00 6.67 0.32 0.45 NSDehydrated 8.67 8.33 8.17 7.83Flavour Canned 8.33 7.66 7.17 7.00 0.48 NS NSDehydrated 8.33 8.17 8.00 7.83Overall Canned 8.21 7.62 7.12 6.87 0.19 0.27 NSacceptabilityDehydrated 8.54 8.25 8.04 7.83Values are mean of 9 replicationsNS= Non Significant Table 3. Effect of storage on the physico-chemical parameters of processed okraPhysico-chemical Products Storage period (months) CD (P<0.05) for CD (P<0.05) for CD (P<0.05) forparameter 0 1 2 3 4 5 6 Process Storage Process X Storageo -5 -5 -5TSS ( Brix) Canned 3.60 2.80 2.40 2.40 2.30 2.30 2.20 0.20 x 10 0.37 x 10 0.52 x 10 Dehydrated 48.00 35.20 32.00 32.00 30.00 29.00 29.00 Moisture (%) Canned 96.94 96.36 95.34 95.21 95.09 94.99 94.92 0.06 0.11 0.15Dehydrated 8.48 8.52 8.56 8.60 8.65 8.70 8.74Ascorbic acid Canned 9.01 7.88 7.03 6.31 5.67 5.15 4.73 0.32 0.59 0.84(mg/100g) Dehydrated 20.40 17.27 14.73 12.55 10.87 9.80 9.06-2 pH Canned 6.78 6.75 6.73 6.72 6.72 6.69 6.67 0.96 x 10 NS 0.02Dehydrated 6.65 6.65 6.67 6.68 6.69 6.69 6.71Protein (%) Canned 0.94 0.98 1.05 1.12 1.15 1.19 1.22 0.04 0.07 0.10Dehydrated 18.86 18.30 18.29 18.28 18.28 18.27 18.26Crude fiber (%) Canned 3.40 2.91 2.55 2.28 2.05 1.84 1.63 0.30 0.57 0.81Dehydrated 50.55 49.53 47.84 46.82 45.84 43.42 40.65Pectin (%) Canned 0.080 0.076 0.072 0.068 0.067 0.065 0.063 0.04 0.08 0.11Dehydrated 2.97 2.82 2.69 2.56 2.37 2.22 2.12Chlorophyll Canned 62.57 55.90 46.86 42.26 35.70 31.23 29.00 0.21 0.39 0.54(mg/100g)Dehydrated 166.75 160.73 151.64 145.03 136.16 129.53 122.76Rehydration ratio Dehydrated 5.89 5.81 5.74 5.71 5.63 5.54 5.47Values are mean of 3 replicationsNS= Non Significant "