Effects of cooking practices (boiling and frying) on the protein and amino acids contents of four selected fishes

This study was aimed to estimate and compare the contents of protein and amino acids in raw, boiled and fried fishes of Indian mackerel “kembong” ( Rastrelliger kanagurta ), sardine ( Sardina pilchardus ), red tilapia ( Oreochromis mossambicusx ) and black tilapia ( Oreochromis mossambicus ). Protein contents of raw mackerel, sardine, red and black tilapia were 8.1±0.0, 8.4±0.1, 9.6±0.4 and 9.0±0.0 percent, respectively. In a boiled fish, the protein contents were 7.9±0.1, 7.7±0.0, 7.5±0.1 and 8.9±0.1 percent, respectively, and for a fried fish the values were 8.6±0.5, 8.9±0.1, 9.1±0.2 and 8.4±0.0 percent, respectively. It was found that there was a significant difference ( p <0.01) in the protein content of the raw fish compared to the heat‐treated ones for all the fishes. The study detected 17 components of essential amino acids (lysine, histidine, threonine, valine, methionine, leucine, isoleucine and phenylalanine) and non‐essential amino acids (arginine, aspartic acid, serine, glutamic acid, proline, glycine, alanine, cystein and tyrosine) in all the fishes. There was no significant difference in amino acids content among the boiled and fried fishes. In conclusion, heat treatment for five minutes in boiling water (100°C) and frying for three minutes in palm oil (160°C) did not alter the quality of protein in all the fishes studied.