Standardization of dehydration techniques in Anachunda (Solanum torvum Swartz.) black nightshade (Solanum nigrum Linn.) and lotus (Nelumbo nucifera Gaertn.)

Abstract

The present investigation on the standardization of dehydration techniques in ‘anachunda’ (Solanum torvum Swartz.) black nightshade (Solanum nigrum Linn.) and lotus (Nelumbo nucifera Gaertn.) was conducted in the Processing Unit and Analytical Laboratory of Department of Processing Technology and in the Laboratory of the Biochemistry Division, College of Horticulture, Kerala Agricultural University, Vellanikkara, Thrissur, Kerala during September 1993 to February 1995. The experiments were laid out in completely randomized design with three replications. Study on standardization of dehydration technique revealed that the superior pretreatments for S.torvum were 0.5 per cent KMS at 850C for three minutes and four per cent brine at 850C for three minutes. It was followed by four per cent brine + 0.5 per cent KMS at 850C for three minutes. In S. nigrum the superior pretreatments were one per cent citric acid 850C for three minutes and four per cent brine + 0.5 per cent KMS at 850C for three minutes. It was followed by four per cent brine at 850C. The superior pretreatments for N. nucifera were four per cent brine + 0.5 per cent KMS at 850C for three minutes followed by 0.5 per cent KMS at 850C for three minutes and one per cent citric acid at 850C for three minutes. Thus the superior pretreatment was four per cent brine + 0.5 per cent KMS at 850C for three minutes on an overall basis. It was followed by 0.5 per cent KMS at 850C for three minutes, one per cent citric acid at 850C three minutes and four per cent brine at 850C for three minutes. The experiment also revealed that microwave dehydration was significantly superior to dehydration in cabinet dryer and sundrying with respect to retention of colour and nutritional qualities. Packaging and storage studies revealed that the dehydrated products with an initial moisture content of 7 + 1 per cent could be stored upto six months without significant deterioration in colour, texture and consumer acceptability. The moisture uptake was not significantly different between the four packages under study viz., polyethylene 80 gauge, polyethylene 100 gauge polyethylene, polyethylene 150 gauge, polyethylene 200 gauge. In economic terms polypropylene 80 gauge bags was found to be the cheapest. The experiment on sensory evaluation of hot oil fried products revealed that on an overall basis the treatments viz., four per cent brine + one per cent citric acid at 850C for three minutes, four per cent brine + 0.5 per cent KMS at 850C for three minutes and 0.5 per cent KMS at 850C for three minutes were significantly superior for getting products with better taste, colour and overall acceptability. It was also found that microwave oven dehydrated products scored better for taste, colour and overall acceptability. The investigations also indicated that tremendous potential exist for exploitation of microwave dehydration technology for the dehydration of vegetables.