Effect of controlled lactic acid bacterial fermentation on the microbiological and chemical qualities of Moroccan sardines (Sardina pilchardus)

Abstract

Lactic acid bacteria (LAB) strains were assayed for the conservation of fresh sardine "Sardina pilchardus". Lactobacillus delbrueckii subsp. delbrueckii was used for inoculation of sardine fillets in a solution of NaCl (5%, w/w) and glucose (4%, w/w) concentration in water. Microbial counts including Standard Plate Count (SPC), LAB, yeasts, coliforms, Salmonella, staphylococci and Clostridium were followed during two weeks of storage at 30 degrees C. Determinations of chemical parameters including pH, dry matter, fat, ash, total nitrogen (NT), total volatile basic nitrogen (TVBN) and trimethylamine (TMA) were carried out under the same conditions. Chemical determinations showed a net pH decrease from an initial value of 6.05 in raw sardine fillets to 4.3 after 16 days of fermentation. Increases in TMA content and TBVN were observed. Microbiological control showed that LAB counts reached a level up to 3.10(9) cfu/g after 4 days of fermentation. After two weeks, fermented fish was free of coliforms and Salmonella. The inhibition of pathogenic microflora including staphylococci and Clostridium was also observed. The results indicated that controlled LAB fermentation could be used as a successful process for biopreservation of sardines produced in huge quantities in Morocco.