Modified BARC Model Dryer Compared with Machanical Dryer and Conventional Sun Drying Based on Extent of Nutrient Loss in Dried Fish Products

Abstract- The main objective of the study was to compare the extent of nutritional loss in seafood caused by drying in a modified BARC model solar dryer with that in an electrical (mechanical) dryer and that by direct drying under sun on a platform. Two products were prepared for the study, viz. dry salted threadfin bream (Nemipterus japonicus) and dried shrimp (Metapenaeus dobsoni).Rate of drying of salted fish or peeled shrimp was highest in electrical dryer, followed by that in solar dryer and was lowest on platform as indicated by the rate of decrease in moisture content and hence, decrease in water activity of the products.

The nutritional parameters, viz. thiamine content, pepsin digestibility and salt soluble protein content, reduced upon drying irrespective of the drying method. Thiamine content of salted fish was reduced from 48.42 μg/ 100 g to around 29μg/ 100 g, pepsin digestibility was reduced from 97.1% to about 82% and salt soluble protein content from about 50% to about 20% upon drying. In the case of dried prawn the variations were: thiamine from about 295 μg/100 g to 200- 208μg/100 g, pepsin digestibility from around 95% to around 77% and salt soluble protein content from about 54% to about around 20%.

Slight increases in moisture content and hence, water activities of both the products were observed during storage for two months, but none of them exceeded maximum limits recommended. There was further reduction in nutritional quality parameters of both the products upon storage which can be attributed to the fairly high storage temperature of 26- 35oC. But the variations between products dried by different methods were only slight indicating that method of drying did not have influence over nutritional quality changes during drying.

Various spoilage indices, viz. peroxide value, thiobarbituric acid value, total volatile base nitrogen content, trimethylamine content, total plate count and total fungal count, increased during storage, but did not exceed the limits generally recommended. Significant reduction in sensory scores could be observed during storage of both the products irrespective of the method of drying, but the scores of the products were all well above the minimum acceptability score even at the end of the storage study period. However, sensory quality parameters of both the products showed significant variations between different drying methods, with electrical dryer giving higher scores, followed by solar dryer, followed by direct sun drying.