Effects Of Bio-preservatives On The Quality Of Hairtail Product

In this paper, hairtail fish balls, one of the typical fish protein products, were chosen as the research object. At the end of their shelf life, selective medium was used to detect the composition of bacterial phase, the morphology of microflora separated from rotten hairtail fish balls was observed. Traditional microbiological assay as well as molecular technology based on16S rDNA were used to identify the dominate spoilage bacteria in hairtail fish balls, which were analyzed by phylogenetic tree. Bio-preservatives such as lysozyme, Nisin, ε-poly-lysine (ε-PL) and hydrosoluble chitosan were selected to determine the optimum concentration range. The Box-Behnken response surface central composite design was applied to optimize the optimal formula of bio-preservatives. Application and effects of the compound bio-preservatives on hairtail fish products were evaluated from several aspects. The main results were presented as follows:1. Bacterial phase analysis through selective medium was carried out that bacteria phase was shown priority to be Bacillus genus (60.7%), followed by Staphylococcus (39.3%). By colony morphology, physiological and biochemical characteristics and molecular biology of16S rDNA, four typical bacterial strains were identified as follows:Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, and Paenibacillus polymyxa. Nisin, lysozyme, ε-PL and hydrosoluble chitosan could significantly inhibited Staphylococcus aureus, Paenibacillus polymyxa, Bacillus cereus and Bacillus subtilis, respectively. And bacteriostatic effects of bio-preservatives enhanced with the increase of concentration.2. The best proportion of compound bio-preservatives was Nisin0.40g/L, lysozyme0.30g/L, ε-PL0.30g/L and hydrosoluble chitosan4.80g/L with the analysis of the Design-Expert software. The inhibition zone of the actual was15.50mm with the optimal formula, which was similar with the model prediction (15.85mm) and significantly tested and verified the validity of the model. The continuity test of bacteriostatic activity indicated that compound bio-preservatives extended the duration of the bacteriostatic activity, and the initial antimicrobial activity of compound bio-preservatives was obviously higher than that of single bio-preservative. The result showed that compound bio-preservatives had certain potential applications and development prospects.3. The addition of the compound bio-preservatives made the hairtail fish protein gel structure be in better order with the gel surface more closely and uniform which effectively improved the physical properties of fish products. Better protein network structure improved the springness and crispness of products and guaranteed products’ commodity value. Compound bio-preservatives effectively improved and maintained the springness and hardness of hairtail protein products, reduced the deterioration trends of whiteness, and maintained sensory quality of protein products during storage in4℃. Compound bio-preservatives significantly inhibited the growth of microorganisms in aquatic protein products, prolonged shelf lifes under refrigerated condition, maintained TVB-N value, TBA value and pH value at lower levels, prevented and delayed the protein degradation and fat oxidation, effectively maintained the quality of hairtail protein products.