Isolamento de bactérias ácido lácticas com atividade antagonista frente a patógenos e caracterização microbiológica e físico-química de amostras de leite in natura e queijos coloniais da região Fronteira Noroeste do estado do RS.

Abstract

Milk is an essential food, rich in nutrients. The cheese, a product derived from milk is protein-fat concentrate also a high nutritional value. The lactic acid bacteria, naturally present in milk, are fundamental for the production of cheeses, because they are responsible for the fermentation process that gives flavor typical. The aim of this study was to isolate lactic acid bacteria with antagonistic activity in relation to Escherichia coli, Listeria monocytogenes, Salmonella Typhimurium and Staphylococcus aureus, characterization the microbiological and physico-chemical of raw milk and cheeses from the northwestern region of Rio Grande do Sul state and the influence of the seasons in these characteristics was studied. For this, were selected ten farmers who manufactured artisan cheese from raw cow milk and without addition of starter cultures. There were two collections (summer/winter) of samples of milk and cheese. The procedure was then the isolation, detection and checking of the antagonistic activity of the fermentation profile of native lactic acid bacteria as well as the microbiological and physic-chemical characterization of milk and cheeses regional. Considering the testes, of lactic acid bacteria isolated, 37,49% premise to be of the genus Lactococcus/Enterococcus and Lactobacillus are 25.89%. The activity antagonist against all tested pathogens was showed for 33,87% isolates and these have homofermentative profile. In general, the samples of milk and cheeses analyzed have low microbiological quality due to high numbers of microorganism hygiene indicator. Was not detected the presence of Salmonella spp. and Listeria monocytogenes in samples of milk and cheese. The high standard deviations for moisture, protein, fat and salt content show that there is a rule for artisanal cheese production in the northwestern region of Rio Grande do Sul state. The composition of milk used for cheese production was varied and this is also observed in the cheeses. The season resulted in microbial diversification milks and cheeses, as well as variation in moisture, water activity and salt content of cheese and the total solids of milk. Bacterial isolates should be further tests for confirmation and species identification.