Determination of shelf life of Yellowfin tuna (Thunnus albacares) with regard to microbial count, histamine level and flesh colour

Yellowfin tuna (YFT) (Thunnus albacares) is among the most popular fish in seafood trade all over the world. The quality of tuna meat is the main determinant of its market price. This study was conducted to determine the shelf life of YFT flesh stored at 0-2oC in terms of microbial total plate count (TPC), histamine levels and flesh colour change within 15 days of storage. Twenty-five YFT samples collected from a seafood processing factory, on the same day they received from the multi-day boats, were used in the study. In each visit, five fish samples were collected with the same catching date (5 days before landing). Samples were vacuum packed and taken to the laboratory where they stored under 0-2oC. All experiments were conducted on 1st, 4th, 7th, 11th, 14th and 15th days of storage. Pour plate method was conducted for total microbial plate count. Histamine content was determined using competitive ELISA method. Flesh colour change was determined by calculating the value of Red, Green, and Blue (RGB) colour ratios of the images using a colour detector mobile application. Results showed that the highest microbial count was exhibited on 7th day of storage and did not exceed more than 105 CFUg-1. Histamine levels were increased up to a maximum mean value of 14.24 ppm during the storage. Microbial counts and histamine results suggest that it is safe to consume YFT within 15 days under 0-2oC storage conditions.