Safety and technological characterization of autochthonous thermophilic lactic acid bacteria and their application in the production of Parmesan cheese

Abstract

Autochthonous lactic acid bacteria (LAB) are present in various foods and mainly in raw milk or in a dairy environment. These cultures may have interesting industrial characteristics, as they can survive in adverse conditions and prevail in this ecosystem. Studies with autochthonous LAB show that they can produce enzymes, vitamins, and flavor compounds, or compounds that exhibit therapeutic effects. Recent, works realized by our research group showed that some autochthonous strains isolated from water buffalo mozzarella cheese are capable of producing bacteriocin as well as some probiotic properties. In this context, the aim of this study is to evaluate the safety and technological characteristics of autochthonous thermophilic lactic acid bacteria (LAB) strains of Lactobacillus helveticus, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. The safety characterization of LAB will be undertaken by verifying the existence of virulence genes, the production of biogenic amines and the antibiotic resistance, as well as the hemolytic activity and the activity of ²-glucosidase, N-acetyl-²-glucosaminidase, ²-glucuronidase enzymes. The technological properties will be assessed by the acidification kinetic, the analysis of the casein hydrolysis, the verification of exopolysaccharide production and the determination of proteolytic and peptidolytics enzymes activities. The strains that are considered to be both safe and with better technological properties, will be selected and applied in the production of Parmesan cheese. One cheese will be produced with commercial strains, and another with the selected strains. After the cheese production, the centesimal composition will be assessed and during maturation the proteolysis of casein will be evaluated, as well as the sensory and microbiological quality of the cheese. With this study, it is hoped to characterize the safe autochthonous LAB cultures which have good technological characteristics for application in the production of Parmesan cheese. The characterization of new strains may expand the possibility of their application by the dairy product industries.