Effects of hygienic handling in combination with potassium sorbate treatment and smoking on the microbial quality and shelf-stability of croaker ( Micropogonias furnieri )

Abstract

Fresh croaker (Micropogonias furnieri) were handled hygienically (i.e. in decontaminated containers) or conventionally (i.e. unhygienically) and dipped for 30 or 60s in 3% (w/v) potassium sorbate (KS) prior to hot-smoking. Changes in microbial, physical and sensory quality attributes during tropical ambient (28±2 °C) storage were investigated. Six bacterial genera of predominantly Enterobacteriaceae were isolated from the fresh samples subjected to hygienic treatment. A more heterogeneous bacterial flora of 11 genera was isolated from conventionally handled samples. Most of the Gram-negative bacteria were eliminated following smoking, resulting in the samples being dominated by Gram-positive bacterial flora consisting of Staphylococcus, Bacillus, Clostridium, Lactobacillus and Streptococcus. However, moulds (Aspergillus niger, Penicillium sp. and Rhizopus stolonifer) constituted the major spoilage organisms. Significant reductions (P=0.05) in total viable counts and coliform bacteria were observed in all samples after smoking. Further reductions occurred in samples held in decontaminated containers prior to smoking. Coliform bacteria were undetected on the 4th day in samples handled hygienically and dipped for 60 s in KS before smoking, but coliform growth and population increase occurred thereafter. The moisture content of the fresh samples was reduced significantly following smoking and tended to increase after about 8 days, but pH decreased slightly. Combination treatments of hygienic handling with extended dipping time (60 s) in KS and smoking exerted the maximum positive impact on the microbial quality and shelf-life of the samples.