Microbiological Quality and Enzymes Activity of Refrigerated Bolti Fish ( Tilapia Nilotica ) Pretreated with Organic Acids

Abstract

This study was carried out to evaluate the microbiological quality and enzymes activity of whole Nile bolti fish (Tilapia nilotica) stored under refrigeration at 4±1°C after immersing in aqueous solutions of acetic acid (1%), citric acid (3%) and mixture of acetic acid (1%) with citric acid (3%) for 5 minutes. Changes in microbiological quality criteria, (total viable bacterial counts (TVBC), psychrophilic bacterial counts (PBC), yeast and mold counts and total coliform count) and activity of catalase and protease enzymes were evaluated during 12 days of storage. Results indicated that, the aqueous solutions of used acids reduced various criteria of spoilage microorganisms. On the other hand, by increasing the storage time of fresh bolti fish at 4±1°C, the microbial counts and both of catalase and protease activity were gradually increased. Whereas, the combination of acetic acid and citric acid are the most effective treatment for reducing catalase and protease activity during storage time up to 12 days. In conclusion, the results found that acetic acid and citric acid solutions, especially in combinations, can be utilized as safe organic preservatives for bolti fish under refrigerated storage up to 12 days.