Survival of listeria monocytogenes in turmeric-salt marinated short mackerel (Rastrelliger brachysoma) under isothermal storage temperature

Abstract

Short mackerel (Rastrelliger brachysoma) is a common fish consumed in Malaysia. The high protein content of fish makes it prone to contamination with bacteria, including Listeria monocytogenes. Therefore, the objective of this study is to control the growth of L. monocytogenes by marinating short mackerel with turmeric-salt and storing at various temperatures. The short mackerel was treated with 70% of ethanol before marinating with turmeric-salt in a ratio (1:1). The short mackerel were inoculated with a concentration of 108 CFU/mL of L. monocytogenes and was stored at 0, 5, 10, 15, 20, and 25˚C for 21 days. The total microbial count and L. monocytogenes count were determined for every three days from 0 days to 21 days. The growth of L. monocytogenes in marinated mackerel was from 4.30 log CFU/g (0 days at 0 ˚C) to 5.22 log CFU/g (0 days at 25 ˚C). While the total of L. monocytogenes counts in non-marinated (control), short mackerel increased significantly based on temperature and time from 4.98 log CFU/g (0 days at 0 ˚C) to 6.22 log CFU/g (0 days at 25 ˚C). These results indicated that the growth of L. monocytogenes in the presence of turmeric-salt slowed compared with the non-marinated product, although the growth of L. monocytogenes was gradually increased throughout 21 days of storage. There was a significant difference (p<0.05) in the growth of L. monocytogenes with the storage temperature. In conclusion, the turmeric-salt marination has the potential to slow the growth of L. monocytogenes in short mackerel by approximately 0.07 log CFU/g-2.81 log CFU/g of log reduction.