Physicochemical and microbiological changes during mullet fish (Feseekh) fermentation by microbial inoculation with Lactobacillus plantarum and Saccharomyces cerevisiae

Probiotics such as Lactobacillus plantarum and Saccharomyces cerevisiae could improve food quality and provide a good health effect for consumers. The objective of this study is to detect the changes during natural and microbial fermentation of roe-free mullet fish (butterfly) conducted by two successive species, bacteria such as L. plantarum (L), and yeast such as Saccharomyces cerevisiae (S), and their mix (M). Physicochemical properties of fermented mullet fish products were monitored. Moisture contents of all fermented products after 5 days ranged from 58.79% to 66.76% due to the salting-out effect. The salt contents and concentrations of microbial fermented butterfly mullet fish treatments were 3.75 and 5.55% (L), 3.56 and 5.10% (S), and 3.82 and 5.40% (M). The pH of natural fermented whole mullet fish (T) was 7.28, while it was observed in the range from 5.84 to 5.11 for the rest treatments (L, S, M, and Control (C)). The TBARS values exceeded 1 mg MDA/kg sample for T and C treatments, while microbial fermented (M, S, and L) treatments were less than 1 mg MDA/kg sample. The highest TVB-N value was observed with the T treatment (253.48 mg/100 g), while L- and M-treatments showed the lowest levels (77.11 and 75.83 mg/100 g, respectively). The single microbial fermented treatments (L and S) had the highest total BAs (spermine, cadaverine, histamine, tyramine) contents at 48.49 and 37.49 mg/kg, respectively. The study found that fermented fish had a higher microbial load in inoculated groups (L, S, and M). Anaerobic bacterial count declined during fermentation. S. aureus and aerobic plate counts in fermented fish products declined after 6 months of frozen storage. In conclusion, the properties of microbial fermented products were improved during the fermentation process than traditionally fermented fish, and proven that microbial fermentation using probiotics is an effective method.