The effect of storage temperature on histamine production and the freshness of yellowfin tuna (Thunnus albacares)

The present study was undertaken to assess the effect of storage temperatures on the shelf life and safety of yellowfin tuna (Thunnus albacares) by studying the changes in microbial, chemical, and organoleptical attributes. Shelf life of yellowfin tuna was determined through changes in total aerobic mesophilic and psychrotrophilic bacterial plate counts, K values, and organoleptic properties, whereas one aspect of its safety was determined through histamine development during storage at 0, 8, and 20°C. The K value increased linearly at a slow rate (2.4%/day, r ² = 0.90, p < 0.05) during storage at 0°C. Based on K value indices, yellowfin tuna maintained an acceptable shelf life for 12, 5 and 1 day at 0, 8, and 20°C, respectively. However, yellowfin tuna were rejected earlier by the sensory panelists than their K value indicated. Histamine development was found to be lower than the Food and Drug Authority (FDA) safety level of 5 mg/100 g fish during storage at 0°C for 17 days. Yellowfin tuna stored at 8 and 20°C became unsafe for human consumption, reaching unacceptable histamine levels after 4 and 1 day, respectively. Aerobic mesophilic bacteria initially dominated the microflora on yellowfin tuna, however, as storage time increased, aerobic psychrotrophic bacteria became dominant at cold storage but the numbers did not exceeded the International Commission on Microbiological Specifications for Foods (ICMSF) limit of 10 ⁷ cfu/g.