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.
Highlights
Fisheries sector is one of the most important food sources throughout the world
The pH started to increase from day 2 to day 7 and indicated the production of alkaline bacterial metabolites in spoiling fish as well as increase in total volatile basic nitrogen (TVBN) [16]
Liquid residual of tuna fish (Euthynnus affinis) collected for seven days during iced storage at 4∘C had shown presence of creatine and phenylalanine compounds derived from biofluids and microbial products, respectively, through LC-MS/MS analysis
Summary
According to statistical data reported by Department of Fisheries, Ministry of Agriculture Malaysia, fish production increased from 2005 to 2014 with marine fish contributing the largest proportion of 1.74 million tons of fish in 2014. Tuna fish (Euthynnus affinis) (Figure 1) is categorized under marine (saltwater fish) that has a high market value. Tuna fish spread widely and almost consists of all coastal and offshore marine waters throughout the Indo-Pacific. Euthynnus affinis is the smallest species of tuna fish with an average length of about 50–150 cm or. The chemical composition of a tuna fish as reported by Suzuki and Kume (1981) [1] is water (71%), protein (21.6%), fat (1.3%), minerals (1.2%), ash (1.45%), vitamin A (0.5%), and vitamin D (1.0%). Various types of dishes and fish product applications make demands of tuna fish increased by years. Preserving fish freshness and quality is of high concern
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