Physicochemical Characterization of Biofluid Metabolites from Liquid Residual of Tuna Fish (Euthynnus affinis) throughout Refrigerated Storage Condition

Abstract

The cold storage condition and use of chemical treatment to preserve the fish appearance sometimes cause difficulties to the consumers to estimate the freshness of fish in the market. However, during fish deterioration, some compound is released or formed due to microbial and biochemical process. Identification of released compound during fish spoilage is a crucial step in understanding the degree of spoilage. This study characterizes the physicochemical changes of metabolites biofluids from liquid residual of tuna fish (Euthynnus affinis) during refrigerated storage condition. Tuna fish were kept in ice at 0°C and stored in cold room (~4°C) for seven days in order to study the changes in fish freshness and loss of quality through the storage period. Liquid residual of fish was collected at 0, 1, 2, 3, 4, 5, 6, and 7 days of storage. LC-MS/MS analysis was carried out to determine the possible dominant compound which was later identified as creatine and phenylalanine. Quantification of creatine and phenylalanine using HPLC with UV detector found that creatine and phenylalanine increased significantly up to day 4 and day 5 upon storage time for creatine and phenylalanine, respectively (p<0.05). The liquid residual pH increased from 6.5 on day 0 to 7.5 on day 7 (p<0.05). Changes in chemical compounds were supported with physical analysis on gills colour of spoilage fish. L⁎ and a⁎ values decreased with storage time from 41.08 to 24.76 and 18.34 to 10.40, respectively, while b⁎ value increased from -3.80 to -0.46 (p<0.05). The finding of biofluid derived compounds was found as useful and alternative indicators of fish freshness in later study on the development of optical biosensor.