Physico-sensory and microbial evaluation of ice stored Nile tilapia fillets (Oreochromis niloticus L.) from Lake Hawassa

Abstract

Fillets from the Nile tilapia (Oreochromis niloticus L.) were obtained from Lake Hawassa, and were exposed to ice storage in five different packages designated as package I (muscle to ice ratio of 1:1 (w/w)), package II (muscle to ice ratio of 1:2), package III (a combination of muscle, ice and water of 1:0.2:0.5 (w/w/w)), package IV (muscle to water ratio of 1:1) and package V (stored in a refrigerator at 4⁰C). Clean fresh fillets contained 5.06 log (c.f.u/g). Fillets stored in ice crystals in the ratio of 1:2 (package II) got spoiled after 24 hours, when the total bacterial count reached 5.31 log (c.f.u/g), while at the ratio of 1:1 (package I), the count reached 5.65 log (c.f.u/g). The fillets from these two packages were organoleptically acceptable for consumption up to the 24th hour of storage and those stored in water at the 1:1 ratio (package IV) were acceptable up to the 15th hour. At rejection, fish exhibited a strong fishy, sulfidy, putrid and ammoniacal odor. The respective counts of total lactics and psychrophiles initially were 1.70 and 4.27 log (c.f.u/g). However, after 24 hours of storage, they reached 2.89 and 5.32 log (c.f.u/g) in package II and 3.68 and 5.46 log (c.f.u/g) in package I, respectively. Our study revealed that the shelf-life of tilapia stored in ice was improved by about 12 hours.

Keywords/phrases: Fillets, Ice storage, Lake Hawassa, Oreochromis niloticus.

Ethiop. J. Biol. Sci., 9(2): 183-193, 2010