Quality of traditionally produced Istrian sausage and identification of autochthonous lactic acid bacteria strains as potential functional starter cultures

Fermented sausages have been manufactured traditionally in the Mediterranean basin. Istrian sausages are one of the many regionally specific products distinguished by the specific traditional recipes and consequentially exceptional sensory characteristics. The aim of this study was to evaluate sensory, physico-chemical and microbiological changes occurring during production and ripening of Istrian sausages made at traditional households, and to compare the results obtained with the identical product produced in industrial conditions. Additional goal was to characterise the autochthonous lactic acid bacteria populations and to obtain the candidate starter strains. Production stages and product ripening parameters could be strictly defined in controlled industrial conditions of the production process, and the results of this study can serve to standardise the production of traditional Istrian sausages. The results from sensory and physico-chemical examination do not show differences in relation to sausages of a similar type investigated in other papers. Lactic acid bacteria were favoured during fermentation at rising salt concentrations, consisting mostly of Lactobacillus strains followed with the abundance of coagulase-negative cocci. Further, we targeted the autochthonous lactic LAB population to select the candidate starter strains for controlled sausage fermentation. Fifty Gram-positive strains with catalase-negative phenotype, rod-shape or cocci morphology, effective acidification kinetics and production of lactic acid identified by sequence analysis of 16S rRNA were considered LAB. The selected LAB strains were able to grow in a range of pH values and high salt concentration important for their metabolic activity during sausage fermentation. According to our results, Lactobacillus sakei, which is a prevalent strain during fermentation of various types of fermented sausages, was frequently detected. Lactobacillus plantarum and Lactobacillus curvatus were also detected in abundance, implying their possible competitiveness among the complex microbial population. Isolated autochthonous strains L. curvatus S30, L. sakei S32 and L. plantarum S50 produced high lactic acid concentrations, tolerated NaCl concentrations present during sausage fermentation, survived at high concentrations of hydrogen ions and inhibited six pathogens associated with contamination of meat products in a strain-specific manner.