Antistaphylococcal potential and application of autochthonous enterococci and lactobacilli in pilot cheese production

Abstract

This study was undertaken to prepare tailor-made starter culture (TMSC) for Karst ewe's cheese production. Therefore, basic technological characteristics (growth ability in milk, acid production, and proteolytic activity) and antistaphylococcal potential were assessed for autochthonous enterococci and lactobacilli. Beside good growth in milk with numbers as high as 8 log CFU ml -1 , certain enterococci and lactobacilli also reduced pH below 5.0 and showed proteolytic activity. In antistaphylococcal testing, only pure strains of enterococci and lactobacilli were moderately antagonistic, but not in coagulated milks and coagulated milk extracts. Enterococci and lactobacilli with most relevant technological/antistaphylococcal properties were combined and tested as TMSC.In control (C) cheese-making, milk was inoculated with TMSC, while staphylococci (SC) cheese-making included contamination with staphylococci. In C trials, high logarithmic counts per g of cheese for enterococci (8.07-8.80) and lactobacilli (7.49-9.98) throughout the ripening period were found, and their authenticity was monitored by RAPD method. Furthermore, cheese extracts failed to inhibit pure cultures of staphylococci, while cheese pieces inhibited Staphylococcus sp. ST17. In SC trials, population dynamics of enterococci (7.81-9.04) and lactobacilli (7.98-9.63) corroborated the results in milk and in C trials, with staphylococci still present at the end of the ripening period but at lower counts than in fresh cheese.

Use of probiotic yeasts with biocontrol activity for fermentation of ewe's milk

“…On the other hand, nowadays, there is an increasing interest in the use of probiotic microorganisms (both lactic bacteria and yeasts) as biocontrol tools for reducing the use of antibiotics and antimycotic agents. 9,10 Moreover, they can also be utilized as an alternative to the heat treatments carried out in some food-processing practices, 11 which can affect chemical and organoleptic characteristics. It could therefore be interesting to evaluate this in the strains used for the fermentation of milk as an alternative for prolonging the shelf life of food products.…”