Effect of natural compounds alternative to commercial antimelanosics on polyphenol oxidase activity and microbial growth in cultured prawns (Marsupenaeus tiger) during chilled storage

Abstract

This work deals with the inhibition of melanosis and microflora of tiger prawns (Marsupenaeus japonicus) from aquaculture, by the use of natural compounds selected on the basis of their antioxidant and/or antimicrobial properties: (i) a commercial formula based on an ester from lauric acid and arginine, (ii) d-gluconic acid, (iii) glucose, (iv) chitosan. Their effect was compared with a commercial formulation based on sulphites. Results showed that sulphites alone inhibited efficiently the PPO activity preventing the melanosis development. d-gluconic acid inhibited partially the enzyme activity, but it did not prevent the development of blackspots. All of selected compounds inhibited the microbial growth (total bacteria count, Pseudomonas spp. and Enterobacteriaceae). The H2S-producing microorganisms seemed to be especially sensitive to these natural compounds, with inhibitions higher than 2 log cycle as caused by gluconic acid. However, the luminescent colonies were practically not affected during storage, while the commercial sulphites inhibited this type of marine bacteria. The acidic nature of some compounds could have favoured the growth of lactic acid bacteria. This fact is important because of the potential biopreservative role of lactic acid bacteria when these types of organisms dominate the microbiota.