Effect of freezing period on chemical composition and microbial load of Nile tilapia (Oreochromis niloticus

Abstract

The study was designed to investigate the effect of frozen storage period on the chemical composition, microbiological organisms of Nile tilapia fish (Oreochromis niloticus) .The fish were collected from Jebel Aulia dam, Khartoum, and were subjected to thirty days of frozen storage period and analyzed at intervals of ten days (0, 10, 20, 30 days). Protein decreases with increasing duration of frozen storage; with the fresh samples (not frozen) having the highest protein content 31.05 ± 0.21% while the least 24.70 ± 0.42% was recorded for fish samples that were frozen for thirty days. Similar results were obtained for the moisture content where the least content was 77.03 ± 0.09% and the highest was 81.75 ± 0.35%. Also the fat content changed from 7.80 ± 0.14% to 1.950±0.07 Mineral composition (Fe, Ca, Mg, P, Zn and I) of the samples showed a slight variation with respect to duration of storage. pH values ranged between 6.3 to 5.3 while the total bacterial coli-form count ranged between 3.6×10 to 2.6×10. it decreased in descending order.