Indian Journal of Natural Products and Resources Vol. 1(1), March 2010, pp. 29-33 Effect of drying on the physico-chemical and organoleptic characteristics of Chayote (Sechium edule Sw.) Kulmeet Kaur, HR Sharma* and Ranjana Verma Department of Food Science & Nutrition College of Home Science, CSKHPKV, Palampur-176062, India. Received 21 July 2008; Accepted 2 January 2009 Chayote (Sechium edule Sw.), a neglected and underutilized fruit grown in lower areas of Himachal Pradesh is rich in neutral and acid detergent fibres but low in protein, fat and available energy. However, the fruit is known for its medicinal value. In view of its poor keeping quality and limited shelf life, the preservation by dehydration of chayote pieces and shreds was attempted at 55, 65 and 75ºC in a mechanical drier. The results of the study revealed that dehydration at 55 and 65ºC yielded better quality products as assessed from the time of drying, colour changes, reconstitution and sensory acceptability. Keywords : Sechium edule, Chow-Chow, Chayote shreds, Chayote pieces, Lonku, Dehydration, Organoleptic characteristics IPC code; Int. cl. 8 A61K 36/00, A23N 12/00 Introduction Chayote or Chow-Chow (Sechium edule Sw.) belongs to gourd family Cucurbitaceae which includes melons, squash and cucumbers. It is a very little known and under utilized fruit consumed locally as a vegetable. However, it is gaining popularity as a food crop worldwide due to its inherent qualities 1. In India it has been grown very successfully in northern and southern areas like Darjeeling, lower areas of Himachal Pradesh and in Karnataka and Kerala 2. Chayote plant (Plate 1) is a climbing shrub with large leaves that form a canopy over the fruit 3. In Himachal Pradesh, chayote is found between the months of September and November where it is locally known as Lonku. It is consumed as a vegetable but not relished much due to its bland taste. This crop has considerable potential for further exploitation 1. However, it has remained neglected and has hardly received any attention from post-harvest technology point of view. To promote its value addition, the authors attempted its dehydration as its pieces and shreds and assessed the effects on their physico-chemical and organoleptic characteristics. Materials and Methods Dehydration of Chayote Optimally mature and tender fruits of chayote procured from the local farmers were divided in to two lots. One lot of thoroughly washed fruits was cut into small pieces with the help of a stainless steel *Correspondent author: E-mail: hrsharma_neugal@rediffmail.com Plate 1 a. Chayote plant bearing fruits; b. Chayote (wholes); c. Chayote (halves)
30 INDIAN J NAT PROD RESOUR, MARCH 2010 knife and another lot was shredded with the help of stainless steel shredder. Potassium metabisulphite @1.5g/kg was added and mixed thoroughly with each lot and allowed to rest for half an hour. Treated samples were dried in the mechanical tray drier maintained at 55, 65 and 75ºC, respectively till no more drying occurred. The dehydrated samples were packed in polyethylene bags and evaluated for their physico-chemical and organoleptic characteristics. Water losses and equilibrium yields Water losses (%) after interval of two hours at three different temperatures (55, 65 and 75ºC) were calculated by subtracting the weight of dried samples at each interval from the initial weight of fresh sample kept for drying. The values are reported as per cent on fresh weight of samples kept for drying. Equilibrium yields(%) in relation to temperature and time of drying of pieces and shreds were calculated by taking the dried weight after every two hours of drying till the completion of drying process and converting the value in to per cent on fresh weight basis. Rehydration characteristics Standard method with partial modification was used to assess rehydration characteristics of dried pieces and shreds of chayote 4. Weighed samples (10g) were taken in a beaker and rehydrated in 100 ml of distilled water at room temperature. The samples were drained after every hour till no more increase in weight occurred. The rehydration characteristics were calculated for different intervals by dividing the increase in weight of sample (g) kept for rehydration by initial weight of sample. The values are reported as Water absorption ml/g. Organoleptic characteristics Dehydrated pieces and shreds (25g) from each drying treatment (55, 65, 75ºC) were reconstituted in tap water (150 ml) for 4hours. The reconstituted samples were cooked into vegetables by using the following recipe: Onion (50g), tomato (50g), cumin seeds 5g, oil (75ml), salt (5g), turmeric powder (2.5g) and garam masala (5g). Onion and cumin seeds were roasted in oil to light brown colour. To this tomato and salt were added and roasted slightly followed by the addition of other ingredients as well as the reconstituted pieces and shreds. The resultant mixture was mixed thoroughly and cooked gently on a slow flame for 15 minutes. Vegetable preparations prepared similarly from equivalent weights of fresh pieces and shreds of chayote were kept as controls. The cooked vegetable preparations were presented to a panel of 10 judges for the assessment of cooking quality by sensory evaluation on a nine point hedonic scale 5. Results and Discussion Evaporative water losses Data presented in Table 1 is showing the effect of drying temperature and duration of drying on the water loss from chayote pieces and shreds. Critical appraisal of data shows that water losses due to evaporation at higher temperature and at each interval of drying are higher for chayote shreds compared to chayote pieces. Also, as the temperature of drying increased the time for drying decreased significantly. The chayote pieces dried at 55 C took more time (16h) for attaining equilibrium in weight with an evaporative water loss of 91.0 per cent. Whereas at the same temperature chayote shreds took less time (14h) to attain equilibrium water loss Table 1 Effect of temperature and time of dehydration on the percent water loss of chayote pieces and shreds Time of drying (hrs) Temperature of drying (ºC) 55 65 75 Water loss (%) Water loss (%) Water loss (%) Pieces Shreds Pieces Shreds Pieces Shreds 0 0 0 0 0 0 0 2 9 16.5 12 23 21 32.5 4 24 33 36 42.5 50 50.5 6 40 56 55 66.5 72 75.7 8 52 68.5 68 82.5 82 91.5 10 72 88.5 78 91.75 92 92.9 12 88 90.75 91 92.5 92.5-14 90 91.9 92 - - - 16 91 0-0 - 0
KAUR et al.: EFFECT OF DRYING ON THE PHYSICO-CHEMICAL & ORGANOLEPTIC OF CHAYOTE 31 of 91.9 per cent. Chayote pieces attained equilibrium water loss of 91.2% in 14h at 65 C and 91.50 % in 10h at 75 C. Whereas, chayote shreds at 65 C and 75 C drying required correspondingly less time i.e. 10 and 8h for attaining equilibrium water loss of 92.50 and 92.90%, respectively. The enhanced losses in water at higher temperatures are attributable to enhanced rate of evaporation resulting in comparatively little lower equilibrium yields of the products at lower temperatures. Whereas, the higher evaporative losses in case of shreds compared to pieces are due to large surface area of shredded chayote exposed to the drying temperatures in the dehydrator. Equilibrium yields The yields of dried pieces and shreds obtained at different temperatures and the time required accomplishing the equilibrium yields are presented in Table 2. The equilibrium yields of the products decreased with the increase in temperature and time of drying. Chayote pieces required 16h at 55 C, 12h at 65 C and 10h at 75 C with equilibrium product yields of 11, 8.8 and 8.5%, respectively. In case of Sample Chayote pieces Chayote shreds Table 2 Effect of drying temperature on the equilibrium yield of chayote pieces and shreds Temperature of drying ( o C) Time required (hrs) Equilibrium Yield (%) 55 16 11 65 12 8.8 75 10 8.5 55 14 9.05 65 10 8.25 75 8 8.10 Plate 2 a-d. Dehydrated chayote pieces; e-h. Dehydrated chayote shreds chayote shreds relatively shorter times were required to achieve equilibrium product yields of 9.05, 8.25 and 8.10%, respectively. The variations in the equilibrium yields identical intervals of drying and at different temperatures may be attributed to the variations in the relative humidity of the circulating air at different temperatures. The products during the courses of drying in general have a tendency to attain equilibrium with the surrounding atmosphere. Physical appearance Physical appearance of fresh and dehydrated chayote pieces dried at different temperatures is shown in Plate 2. From the physical appearance of the dehydrated samples it was observed that at 75 C chayote pieces and shreds became discolored towards brownish tint but the change was little more pronounce in case of pieces. However, the samples dehydrated at 55 and 65 C were lighter in colour and acceptable in their appearance. Darkening of colour at higher temperature is attributable to non-enzymatic browning. Although, satisfactory drying in relation to the quality of the product could be achieved both at 65 and 55 C but drying at low temperature (55 C) may be costly due to high-energy costs for running the drier for longer duration to achieve through drying. Rehydration characteristics The data pertaining to the rehydration characteristics of pieces and shreds are presented in Table 3. The rate of hydration of dehydrated pieces and shreds increased with the increase in the duration of soaking in plain water. It increased at a faster rate in shreds as compared to pieces but upon full saturation the dehydrated pieces came to equilibrium at higher water absorption (5.24 ml/g) as compared to dehydrated chayote shreds (3.50ml/g) The higher water absorption behaviour at slow rate of absorption of pieces, may be attributed to the intactness of tissue cells in pieces and higher diffusion distance. Table 3 Effect of drying temperatures on the water absorption (ml/g) characteristics of dehydrated chayote pieces and shreds Product Water absorption (ml/g) Time (hrs ) 1 2 3 4 5 6 7 8 Chayote Pieces 55 o C 1.52 2.44 3.38 4.12 4.58 5.265 5.63 6.07 65 o C 1.50 2.35 3.25 4.00 4.38 5.15 5.20-75 o C 1.20 2.30 2.90 3.20 3.50 4.20 4.20 - Chayote Shreds 55 o C 2.07 2.63 3.34 3.47 3.48 3.50 3.50 --- 65 o C 2.00 2.58 3.25 3.40 3.45 3.48 3.49 --- 75 o C 1.89 2.40 2.45 2.50 3.05 3.10 3.10 ---
32 INDIAN J NAT PROD RESOUR, MARCH 2010 Fig. 1 Effect of different temperatures on the organoleptic characteristics of chayote pieces Fig. 2 Effect of different temperatures on the organoleptic characteristics of chayote shreds This in case of shreds follows an opposite trend due to more disruption of tissues and lower distance of diffusion. Variable rehydration characteristics (water absorption) of air dried, solar cabinet dried and direct sun dried vegetables as 3.3, 2.6 and 2.9ml/g, respectively was also reported by other worker 6. Organoleptic characteristics Vegetables prepared from fresh and reconstituted dehydrated chayote pieces and shreds dried at different temperatures (55, 65 and 75 C) when subjected to sensory evaluation after cooking by a panel of 10 judges revealed that the overall acceptability of fresh chayote pieces was slightly higher (7.76) as compared to fresh chayote shreds (7.67) but significantly higher than the dehydrated chayote pieces and shreds (Fig. 1 and 2). However, the overall acceptability between chayote pieces and between shreds dried at 55C and 65 C did not differ much. Chayote pieces and shreds dried at 75 C were rated as lowest (5.99 and 5.77) in terms of overall acceptability ratings. This may be attributed to the reason that at this temperature the product became little brown in colour, with little hard texture and poor reconstitution. Conclusion The findings of this investigation are concluded with the remarks that the chayote preserved by dehydration during the peak season can be used a vegetable in the off season. Explorative studies on the food applications of dehydrated chayote in Indian confections, soups and other foods need to be undertaken to increase the demand and marketing
KAUR et al.: EFFECT OF DRYING ON THE PHYSICO-CHEMICAL & ORGANOLEPTIC OF CHAYOTE 33 potential of chayote. This will also help the consumers to harvest and harness the therapeutic potential of this vegetable through out the year. References 1 Aung Louis H, Ball Amelia and Kushad Mosbah, Developmental and nutritional aspects of chayote (Sechium edule, Cucurbitaceae), Econ Bot, 1990, 44 (2), 157-164. 2 Nath P, Cho-cho can be a popular vegetable, Indian Hort, 1971, 16 (3), 10. 3 Rafael Lira Saade, Chayote Sechium edule (Jacq.) Sw, Promoting the conservation and use of underutilized and neglected crops, 8. Institute of Plant Genetics and Crop Plant Research, Gatersleben/International Plant Genetic Resources Institute, Rome, Italy, 1996. 4 Ranganna S, Handbook for analysis and quality control of fruits and vegetables 11th edition, Tata McGraw Hill Publication Company Limited, New Delhi, 1986. 5 Larmond E, Laboratory methods for sensory evaluation of fruits, Research Branch, Canada Department of Agriculture, Ottawa, publication, 1977. 6 Jayaraman KS, Das Gupta DK and Babu Rao N, Quality characteristics of some vegetables dried by direct and indirect sun drying. Indian Food Packer, 1991, 45, 16-23.