Microbial diversity and volatile odour-active compounds of barrelled ewes' cheese as an intermediate product that determines the quality of winter bryndza cheese

Abstract

Microbial diversity and volatile odour-active compounds were studied in barrelled ewes' cheese, which is a long-ripened intermediate product in the production of winter bryndza cheese, a type of PGI Slovakian bryndza cheese produced from unpasteurized ewes' milk. Microbial consortia were studied by both culture-based and culture-independent approaches. Microbiological analysis demonstrated that lactococci, lactobacilli and Geotrichum spp. were dominant, while levels of coliforms and coagulase-positive staphylococci were acceptably low. Culture-independent analysis facilitated identification of 26 prokaryotic taxa, with the majority of clones being Lactococcus lactis subsp. lactis and Streptococcus thermophilus, and 23 eukaryotic taxa, with the majority of clones being members of Galactomyces/Geotrichum group. Profiles of odour-active compounds were studied using gas chromatography – olfactometry supported by gas chromatography – mass spectrometry. Thirty-nine odour-active compounds, or mixtures in case of co-elution, were identified. Butanoic acid, ethyl butanoate, isovaleric acid, hexanoic acid, octanoic acid, decanoic acid, methyl octanoate, ethyl hexanoate, ethyl octanoate, p-cresol, and δ-decalactone were detected at high or moderate intensities in all samples. The data obtained demonstrate that barrelled ewes' cheese is a product with specific microflora and a very specific rich profile of odour-active volatile compounds.