Queijo Serra da Estrela PDO Cheese: Investigation into Its Morpho-Textural Traits, Microbiota, and Volatilome

Abstract

Queijo Serra da Estrela is a PDO Portuguese cheese produced through coagulation of raw ewe’s milk using cardoon (Cynara cardunculus L.) flowers. The present research was aimed at depicting an up-to-date and comprehensive overview of the microbiota of Queijo Serra da Estrela cheese. To this end, viable counting and metataxonomic analysis were carried out on cheeses sampled from four Portuguese artisan producers. Physico-chemical and morpho-textural analyses were also performed, together with the analysis of volatile organic compounds (VOCs). Finally, non-starter lactic acid bacteria (NSLAB) isolated from the cheeses were characterized for their enzymatic activities using a semi-quantitative method. According to the metataxonomic analysis, Lactococcus lactis and Lactococcus piscium were the species occurring at the highest relative abundance. The isolates collected from the cheeses were assigned to Enterococcus durans, Enterococcus faecalis, Enterococcus faecium, Enterococcus lactis, Levilactobacillus brevis, Latilactobacillus graminis, Leuconostoc mesenteroides, and the Lacticaseibacillus casei group. The enzymatic characterization of these cultures highlighted esterase, aminopeptidase, acid phosphatase, beta-galactosidase, alpha-glucosidase, and beta-glucosidase among the major enzymatic activities. Fungal populations were dominated by Debaryomyces hansenii and Kurtzmaniella zeylanoides; however, species rarely found in cheese (e.g., Candida boidinii, Vishniacozyma victoriae, and Starmerella) were also detected. The volatile compounds characterizing the analyzed cheeses were carboxylic acids and esters, followed by carbonyl compounds and alcohols.

Technological and Enzymatic Characterization of Autochthonous Lactic Acid Bacteria Isolated from Viili Natural Starters

“…The beta-galactosidase activity exhibited by Enterococcus spp. is extensively documented in the literature, thus confirming their adaption to the dairy environment [57,59,60]. Of note, a low beta-galactosidase activity exhibited by Lactococcus spp.…”

“…is widely documented in the literature [55][56][57] and considered as a desirable trait for dairy starters [55]. Conversely, the activity of other aminopeptidases is less frequently detected [57,58]. Of note, isolates E. durans 4.4 and L. lactis 4.7 and 4.12 exhibited a positive reaction for valine arylamidase.…”

“…and Enterococcus spp. is widely documented in the literature [55][56][57] and considered as a desirable trait for dairy starters [55]. Conversely, the activity of other aminopeptidases is less frequently detected [57,58].…”