No abstract

The production of ovine or caprine milk cheeses with thistle rennet is a common practice in the Mediterranean basin, especially in the Iberian and Italian Peninsulas. In these latter geographical areas, numerous Designation of Origin (PDO) or Protected Geographical Indications (PGI) cheeses are traditionally manufactured, including Queijo de Azeitão PDO cheese, produced in Portugal. The aim of the present study was to obtain information on bacteria and yeast communities harboured in Queijo de Azeitão PDO cheese through viable counting and, for the first time, via metataxonomic analyses.Moreover, solid phase microextraction (SPME) technique was applied to characterize Queijo de Azeitão PDO cheese volatile compounds. Cheese wheels were collected from three different artisan producers located in Portugal. Concerning microbiota, a simple composition was shared by the three producers, whose cheese manufactures were dominated by the presence of Leuconostoc mesenteroides, Lactococcus lactis, Lacticaseibacillus zeae, Lentilactobacillus kefiri, Serratia spp., Lactiplantibacillus plantarum, and Lactilactobacillus sakei. The mycobiota composition showed the neat dominance of Yarrowia lipolytica, followed by Candida ethanolica, Kurtzmaniella zeylanoides, Geotrichum candidum, Galactomyces geotrichum, Kluyveromyces lactis, and Geotrichum silvicola. The volatile profile analysis allowed to identify 24 different compounds: 7 acids (acetic acid, isobutyric acid, butanoic acid, 3-methylbutanoic acid, 2methylbutanoic acid, 4-Methyl-2-oxovaleric acid, and hexanoic acid), 7 esters (butyl acetate, ethyl butyrate, propyl butyrate, ethyl exanoate, isopentyl isobutyrate, 2-nonanone, and ethyl octanoate), 4 alcohols (n-propanol, 2-pentanol, 3-Methyl-1-butanol, and 2-heptanol), 3 ketones (2-butanone, 2-pentanone, and 2-heptanone), 2 aromatic hydrocarbons (benzene and toluene), 1 aldehydes (3-methyl-butanal). The most represented volatile organic compounds (VOCs) were 2-butanone, butanoic acid and hexanoic acid. A positive correlation between Lent. kefiri and hexanoic acid and isopentyl isobutyrate was observed. Whereas Y. lipolytica displayed the highest number of positive correlations with 3-methylbutanal, 2-pentanone and 2-pentanol. It is noteworthy that, to the authors' knowledge, this is the very first detection of Lent. kefiri in raw ewe's milk cheese coagulated with vegetable rennet. The presence of Lent. kefiri in Queijo de Azeitão PDO cheese deserves a further in depth, since in kefir, this species, together with L. kefiranofaciens, L. kefirgranum, and L. parakefiri, contributes to the production of health-promoting exopolysaccharides with acknowledged antioxidant, antitumor, antimicrobial, cholesterol reducing and immune-modulating properties. The detection of Lent. kefiri in Queijo de Azeitão PDO cheese represents an absolute novelty, which suggests that this cheese could have still unknown beneficial effects on the health of consumers. Further research is needed to study the dynamics of microbial communities during manufactur...

Is there any still undisclosed biodiversity in Ciauscolo salami? A new glance into the microbiota of an artisan production as revealed by high-throughput sequencing, Meat Science (2020),

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The quality of sourdough bread mainly depends on metabolic activities of lactic acid bacteria (LAB). The exopolysaccharides (EPS) produced by LAB affect positively the technological and nutritional properties of the bread, while phytases improve the bioavailability of the minerals by reducing its phytate content. In the present study, a pool of 152 cereal-sourced LAB were screened for production of phytases and EPS for potential use as sourdough starter cultures for the baking industry. There was large heterogeneity in the phytase activity observed among the screened isolates, with 95% showing the ability to degrade sodium phytate on plates containing Sourdough Simulation Medium (SSM). The isolates Lactobacillus brevis LD65 and Lactobacillus plantarum PB241 showed the highest enzymatic activity, while the isolates ascribed to Weissella confusa were characterized by low or no phytase activity. Only 18% of the screened LAB produced EPS, which were distinguished as ropy or mucoid phenotypes on SSM supplemented with sucrose. Almost all the EPS producers carried one or more genes (epsD/E and/or epsA) involved in the production of heteropolysaccharides (HePS), whereas the isolates ascribed to Leuconostoc citreum and W. confusa carried genes involved in the production of both HePS and homopolysaccharides (HoPS). Monosaccharide composition analysis of the EPS produced by a selected subset of isolates revealed that all the HePS included glucose, mannose, and galactose, though at different ratios. Furthermore, a few isolates ascribed to L. citreum and W. confusa and carrying the gtf gene produced β-glucans after fermentation in an ad hoc formulated barley flour medium. Based on the overall results collected, a subset of candidate sourdough starter cultures for the baking industry was selected, including Lb. brevis LD66 and L. citreum PB220, which showed high phytase activity and positive EPS production.