Studies on the Selection of Propionic Acid Bacteria for Rindless Semi-Hard Cheeses

Modern cheese-making trends require a specialized approach to domestic starter cultures adapted to specific cheese production parameters. Studying and systematizing the properties of collection strains of propionic acid bacteria will enable their use in specific technological schemes of production, thereby increasing stability and reducing the risk of defects. The aim of the study is to identify strains of propionic acid bacteria from the VNIIMS microorganism collection that possess industrially significant properties and are promising for the production of semi-hard cheeses with low-temperature second heating. Ten strains of propionic acid bacteria were investigated. Gas-forming activity was determined using graduated Dunbar vessels; antagonistic activity of the main and protective starter microbiotas against the strains was assessed by the well diffusion method; development in model nutrient media with varying pH levels, nitrate concentrations, lysozyme, and salt was measured spectrophotometrically at a wavelength of 600 nm. In cheeses, the dynamics of the development of the studied bacteria and the formation of organoleptic properties were evaluated using standardized methods. Based on gas-forming activity results, 6 promising strains of propionic acid bacteria were selected for further studies of technologically significant properties and cheese production trials. For active gas formation, the investigated strains require nitrogenous substances in an accessible form. Active acidity below 5.6 units was a critical factor for their development. Lysozyme at a dose of 2.5 g/100 L had no negative effect on the development of propionic acid bacteria, while nitrates at doses of 5–15 g/100 L reduced the growth rate of most selected strains in the majority of cases. Protective cultures Lacticaseibacillus rhamnosus, Lacticaseibacillus casei, Lacticaseibacillus paracasei exhibited selective antagonistic effects on some of the studied strains, while Lactiplantibacillus plantarum cultures inhibited their development. Antagonism toward propionic acid bacteria from the main starter microbiota – lactococci – is strain-specific. Cheese ripening with the studied bacteria under optimal temperature regimes in polymer packages selected for gas permeability influenced the development of the eye pattern in the cheese matrix, while the use of concentrated brine during salting contributed to reducing the number of eyes in the sub-cortical layer. Promising strains of propionic acid bacteria were selected based on their gas-forming ability and resistance to adverse environmental factors, which, in combination with targeted use of specific technological techniques, ensure cheese quality stability.