EFFECT OF SALT CONTENT AND FERMENTATION TIME ON PHYSICO-CHEMICAL PROPERTIES OF FERMENTED FISH SAUCE

Abstract

Present study was undertaken to prepare and evaluate quality of fermented fish sauce prepared from Nile tilapia fish. Nile tilapia (Oreochromis niloticus) was collected from Regional Agricultural Research Station, Tarahara, Sunsari. Fish sauce was prepared by fermenting the fish with varying salt concentrations. The salt concentration were varied as salt:fish = 1:1, 1:2, 1:3, 1:4 and 1:5. These samples are denoted by sample A, sample B, sample C, sample D and sample E respectively. Periodic chemical analysis of the samples were done at an interval of 15 days up to day 90 and at an interval of 30 days up to day 180. Fish sauce thus obtained was ripened in direct sunlight and caramel color was added. Chemical analysis showed the periodical change in proximate composition of different samples undergoing fermentation. Sample of ratio 1:1 and 1:2 showed no fermentation at all due to very high salt concentration. 1:3 and 1:4 showed proper fermentation pattern whereas 1:5 was observed to be undergoing spoilage. Although sample with ratio 1:3 and 1:4 showed similar specs, from the statistical analysis, 1:3 was found to be best among all other samples. The moisture content, crude protein content, percentage acidity, pH and percentage ash content of sample with ratio 1:3 was found to be 67.28%, 23.72% (wb), 0.53%, 5.32 and 23.46% respectively whereas that of the control sample was found to be 67.23%, 22.21% (wb), 0.58%, 5.19 and 24.76% respectively. From two tail paired t-test of Sample of ratio 1:3 and control sample, similarity was observed in terms of protein content and ash whereas significant differences in terms of acidity, pH and moisture content. Also the proximate composition of sample C was in compliance with FDA, The Philippines standards. Microbiological test denoted the presence of lactose fermenting bacteria. E. coli was absent in fish sauce so prepared. Caramel was added in the best sample, until its color seemed to be similar to that of commercial fish sauce. Filtration method was implied but clarity could not be obtained. By using suitable clarifier there is good possibility of commercial production of fermented fish sauce from Nile tilapia in Nepal.