Efficacy of Lactoperoxidase System-Whey Protein Coating on Shelf-life Extension of Rainbow Trout Fillets During Cold Storage(4 °C)

The growth and metabolism of gram-negative microorganisms are widely recognized as important reasons for the spoilage of fish and fish product. Based on antimicrobial activity of lactoperoxidase system (LPOS) against gram-negative bacteria, the present study investigated the effect of incorporation of LPOS at concentrations 0 (control), 1.25, 2.5, 5 and 7.5 % (v/v) into whey protein solution as novel antimicrobial coating strategy for rainbow trout (Oncorhynchus mykiss) preservation under refrigeration temperature (4 ± 1 °C) over a 16-day period. During storage of trout fillets, control and 1.25 % LPOS-treated samples reached undesirable levels of rancidity (p < 0.05) at 12th and 16th days, respectively, whereas the higher concentrations showed to be more efficiently stable (p < 0.05) in sensory, chemical (total volatile basic nitrogen (TVB-N) and pH) and microbiological analyses (mesophilic bacteria, psychrotrophic bacteria, Pseudomonas spp. and specific spoilage bacteria). Lipid oxidation in the fillets was not affected significantly by LPOS treatment. The LPOS-whey protein coating also reduced total specific spoilage organisms (Shewanella putrefaciens and Pseudomonas fluorescens) of the fillets more than 1.5 log by the end of storage. The shelf life of samples was extended approximately from 12 days to at least 16 days in the presence of the LPOS. These results indicated the significant antimicrobial activity of the LPOS-whey protein coating solution for refrigerated fish fillets.