Proximate and Mineral Quality Changes in Fillets of Three Fish Species (Mugil cephalus, Chrysichthys nigrodigitatus and Oreochrumis niloticus) at Frozen Storage (Sub 0°C)

Abstract

The proximate and mineral composition of fillets from two brackish water fish species (Mugil cephalus and Chrysichthys nigrodigitatus) obtained from the wild were compared with fillets from farmed fresh water fish species (Orechromus niloticus) fed commercial diet. The study also investigated the effect of frozen storage on the proximate and mineral composition of the fillets of these fishes. Analysis was carried before and after frozen storage using standard methods recommended by AOAC. Comparisons among sample means were made by one-way analysis of variance (ANOVA) at 5% confidence level. The mean ash content in brackish water fish species was 1.71±0.03% and 0.86±0.02% in fresh water fish species. Similarly, dry matter content was 23.84±0.05% in brackish water fish species and 8.81±0.24% fresh water fish species. The concentration of calcium ranged from 70.14±2.30 in brackish water fish species to 94.86±0.43 mg/100g in fresh water species, while the level of magnesium was 34.80±1.30 in brackish water species and 32.00±2.30 mg/100g in fresh water species. The level of potassium in brackish water fishes was 254.66±0.04 and 150.06±0.40 mg/100g in fresh water species. The concentration of sodium was 141.20±57 mg/100g in brackish water fish species and 57.20±0.20 mg/100g in fresh water fish species, concentration of phosphorus was 150.93±0.31 in brackish water fish species and 94.67±0.43 mg/100g in fresh water fish species. The percentage protein in Mugil cephalus was 36.14±0.39% before freezing and 36.05±1.81% after freezing while in Chrysichthys nigrodigitatus it was 36.85±0.20% in fresh samples and 36.63±0.20% after frozen storage. The protein content in O. niloticus varied between 41.50±0.40% before and 41.42±0.40% after frozen storage. The concentration of sodium in fillets of M. cephalus varied from 142.67±0.24mg/100g before storage to 140.33±0.11mg/100g after storage. The mean concentration of sodium in the fillets of C. nigrodigitatus before freezing was 139.73±0.90mg/100g and 136.67±0.23mg/100g after freezing. The concentration of sodium in O. niloticus was 57.20±0.24 mg/100g before and 56.07±0.11mg/100g after freezing. In conclusion, all the fish under study belonged to high protein low fat category. Under the experimental conditions, frozen can be effectively used to preserve protein, dry matter, sodium, magnesium and potassium.