The occurrence and growth of microorganisms during the fermentation of fish sausage

Minced fish (mullet) sausage mixes containing added sugar, salt, nitrate, nitrite and spices were fermented (48 h, 30 degrees C) by indigenous flora or by a starter culture (Pediococcus acidilactici) and the microbial ecology and behaviour of various bacteria was monitored. Pediococcus pentosaceus and Lactobacillus plantarum dominated the indigenous fermentation, achieving populations of 10(7)-10(8) cfu/g by 48 h, and decreasing the pH of the mix to 4.5-4.7. Significant growth (10(5)-10(7) cfu/g) of Staphylococcus warneri, Staphylococcus aureus, Staphylococcus epidermidis. Micrococcus varians and Micrococcus luteus also occurred during this fermentation. Less growth was exhibited by Bacillus megaterium and yeasts. Pediococcus acidilactici dominated the fermentation when it was inoculated as a starter culture, but indigenous lactic acid bacteria (P. pentosaceus and L. plantarum) also grew to 10(7)-10(8) cfu/g. The growth of other bacteria and yeasts was restricted during fermentation with starter culture. Inoculated Escherichia coli, Salmonella typhimurium, Salmonella sofia, and Staphylococcus aureus grew to 10(6)-10(7) cfu/g in the sausage mix during indigenous fermentation. Lesser growth occurred for Bacillus cereus, Clostridium perfringens and Vibrio parahaemolyticus. Growth of these bacteria was significantly inhibited in sausage mix fermented with P. acidilactici.