The main purpose of the study was to observe the nutritional value of unfrozen fish such as Rui (Labeo rohita), Catla (Catla catla), Mrigal carp (Cirrhinus cirrhosus) and to evaluate the effect of freezing condition for 1st, 2nd and 3rd weeks at (-18 °C). The average body weights of the samples were 900gm, 800gm, and 950 gm for Rui, Catla, and Mrigal, respectively. All fish samples collected from the regional market of Tangail and Rangpur district in Bangladesh. The samples were analyzed after

more »

... week interval of up to three weeks. The moisture content of natural and cultivated rui, catla and mrigal were 77.06%, 73.50%, 75.21% and 75.70%, 74.41%, 74.35% respectively in normal condition. These decreased with rising freezing time in 3rd weeks. There were 73.66%, 72.41%, 73.97%, and 71.30%, 73.15%, 72.06%, respectively. In addition, The protein content of natural and cultivated rui, catla and mrigal were noticed 18.55%, 20.19% ,19.85% and 17.34%, 19.45%, 19.35% respectively in normal condition and these declined with increasing frozen storage on 3rd weeks , these values were 17.15% 18.25% ,17.50% and 16% 17.65%,17.48% respectively. Moreover, the lipid content of natural and cultivated rui, catla and mrigal were 1.29%, 2.50%, 1.33%, and 5.67%, 4%, 4.78% respectively in normal condition and after 3rd weeks there were 0.60% 1.48% ,1.15% and 5% , 2.8% ,4.2% respectively. The ash content of natural and cultivated rui, catla and mrigal were 0.99%, 1.28%, 0.88% and 0.95%, 0.81%, 0.91% in unfrozen condition and 1.20%, 1.88%, 1.80% and 1.24%, 1.92%, 1.73% respectively were observed after three weeks. The maximum values of extract release volume, swelling capacity recorded for fresh samples and decreased with freezing times. However, at the end of the study, remarkable change was observed between a normal sample and frozen samples after one, two, and three weeks. Finally, the study showed that the biochemical composition of fish muscles influenced by freezing temperature and time.