Quality changes in Tilapia (Oreochromis niloticus) after delayed icing and subsequent storage in ice

Abstract

Quality changes in tilapia (<i>Oreochromis niloticus</i>) iced directly on harvesting were compared to those occurring when icing was delayed. Chemical and sensory examinations showed that the shelf life of tilapia was 26 days when iced immediately. 20 days and 16 days with 4 and 8 hours delay, respectively. Fish kept at ambient temperature for 12 hours were rejected after one day in ice. These results suggest that for every hour delay in icing the effective shelf life is reduced by approximately one day up to the 8th hour delay. Total volatile nitrogen values increased with storage time. Likewise, K-value and hypoxanthine values increased as storage time increased. The initial bacterial load ranged from 103- 104 cfu/g of fish with H2S-producers count of less than 100 cfu/g of fish. At rejection, the microbial load was 108~109 cfu/g of fish with HgS-producers count of 106-107 cfu/g. The typical off odours of naturally spoiling fish have been reproduced in blocks of sterile muscle by organisms such as <i>Alteromonas putrefaciens, Pseudomonas sp, pseudomonas maltophilia, Pseudomonas flourescens</i> and <i>pseudomonas stutzeri</i>.