Quality evaluation of value added products with marine and fresh water fish

Abstract

Fish is recognized as an excellent source of protein, containing all the ten essential amino acids in desirable concentrations for human beings and available at cheaper rate. The present study, on “Quality evaluation of value added products with marine and fresh water fish” was aimed at evaluating the nutrients and developing products from four fish varieties namely pink perch (Nemipterus raponicus) and silver belly (Gerres filamentoses) belonging to marine species and tilapia (Tilapia mossambica) and katla (Catla catla) of fresh water species. Thus, in addition to the role of income generation, value addition helps to increase the acceptability of the fishes which are presently under utilized. The fresh fish varieties were analysed for chemical constituents like moisture, fat, protein, calcium, phosphorus, iron, vitamin A and peroxide value. Marine fish were found to be rich sources of calcium, phosphorus iron and fat, whereas fresh water fish were rich in protein and vitamin A. Fat content was comparatively low. Yield of fish muscle was found to be high in fresh water species like katla (78 per cent) and tilapia (75.5 per cent). Higher peroxide value was observed in marine varieties. The fish products like cutlet and stick were prepared following standard procedures and were packed in polythene covers and stored for a period of two months. The peroxide value of the products were found to increase with the storage period with significant variation. Products made out of pink perch had the highest peroxide value throughout the storage period and the lowest was in silver belly. Organoleptic evaluation of the products were carried out using a 9-point hedonic scale. Qualities such as appearance, colour, flavour, texture and taste of the developed products were evaluated for a period of two months at fortnightly intervals. The sensory qualities were found to decrease during storage with significant variation. Fish cutlets and sticks made of katla fish had the highest acceptability throughout the storage period. Microbial enumeration of the products revealed that there was a gradual increase in the microbial population with the storage period. Maximum bacterial count was in cutlets made of pink perch initially (1.33x105cfug-1) and finally (10.66 x105cfug-1). Minimum bacterial load was for katla. There was no significant variation in the bacterial load of fresh water fish cutlets but significant variation was observed in marine fish cutlet with pink perch showing significantly high bacterial load. Fungal population was detected in cutlets after 15th day of storage without any significant variation, but after 30 days, cutlet made of pink perch showed significantly high fungal population. Maximum yeast population was also in pink perch cutlet (2.66x103cfug-1) In fish stick also after 60 days of storage, bacterial count was maximum in pink perch (9.00x105cfug-1), fungal count and yeast count 7.33x103cfug-1 and 2.00x103cfug-1 respectively. The shelf life of the products with acceptable maximum total plate count was for 30 days. After 30 days of storage, the products had a total plate count higher than 5x105cfug-1 and also higher peroxide value which is an indication of developing rancidity of fats. This was reflected in their lowered organoleptic qualities with storage period. Katla fish products showed highest overall acceptability may be due to their comparatively low fat content in fish muscle (2.5g 100g-1). After two months of storage the products were found to be slimy with unpleasant odour. Computation of nutritive value of cutlets per packet (4 cutlets, 20g each) revealed a high protein content in tilapia (11.92g), calcium in pink perch (498.24mg), phosphorus in silver belly (382mg), iron in silver belly (2.96mg) and vitamin A in katla (93.12µg). Nutritive value of fish stick per packet (4 sticks, 25g each) revealed a high protein content in tilapia (16.36g), calcium in pink perch (698.12mg), phosphorus in silver belly (519.68mg), iron in silver belly (2.84mg) and vitamin A in katla (72.96µg) respectively.