Dataset Information

Characterization of the fungal microflora in raw milk and specialty cheeses of the province of Quebec.

ABSTRACT: The cheese microbial ecosystem is complex, and the presence of non-starter adventitious microorganisms in milk may have an influence on the organoleptic characteristics of cheese. The aim of this study was to analyze the composition and diversity of the fungal flora of raw milk destined for cheesemaking from 19 dairy farms in Quebec and to monitor their evolution throughout ripening. Six hundred ten yeast and mold isolates were collected from raw milk and raw milk cheeses over a 9-month period. Based on the sequences of the rDNA ITS1-5.8S-ITS2 region, 67% of the raw milk isolates were yeasts, which were assigned to 37 species across 11 genera, while 33% were molds, which were assigned to 33 species across 25 genera. A semi-quantitative analysis of the yeasts and molds in the raw milk from four farms was performed over a 5-month period. The composition and diversity of the fungal microflora were totally different for each farm, each of which had a unique species profile. To determine whether adventitious yeast strains from the milk could develop in raw milk cheese, a multilocus-sequence-typing (MLST) analysis was performed on 13 Issatchenkia orientalis (syn. Pichia kudriavzevii, anamorph: Candida krusei) isolates. The same MLST genotypes were identified for strains independently isolated from raw milk and raw milk cheese from a farm processing its own milk. This study contributes to the understanding of the natural fungal microflora of raw milk and suggests that non-starter yeasts and molds can transfer from raw milk to raw milk cheese and may influence cheese ripening. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s13594-011-0051-4) contains supplementary material, which is available to authorized users.

SUBMITTER: Lavoie K

PROVIDER: S-EPMC3478505 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature

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Characterization of the fungal microflora in raw milk and specialty cheeses of the province of Quebec.

Lavoie Karine K Touchette Marilyne M St-Gelais Daniel D Labrie Steve S

Dairy science & technology 20111229 5

The cheese microbial ecosystem is complex, and the presence of non-starter adventitious microorganisms in milk may have an influence on the organoleptic characteristics of cheese. The aim of this study was to analyze the composition and diversity of the fungal flora of raw milk destined for cheesemaking from 19 dairy farms in Quebec and to monitor their evolution throughout ripening. Six hundred ten yeast and mold isolates were collected from raw milk and raw milk cheeses over a 9-month period. ...[more]

PMID: 23125908

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Project description:Among the bacterial genera that are used for cheese production, Lactobacillus is a key taxon of high industrial relevance that is commonly present in commercial starter cultures for dairy fermentations. Certain lactobacilli play a defining role in the development of the organoleptic features during the ripening stages of particular cheeses. We performed an in-depth 16S rRNA gene-based microbiota analysis coupled with internally transcribed spacer-mediated Lactobacillus compositional profiling of 21 common Italian cheeses produced from raw milk in order to evaluate the ecological distribution of lactobacilli associated with this food matrix. Statistical analysis of the collected data revealed the existence of putative Lactobacillus community state types (LCSTs), which consist of clusters of Lactobacillus (sub)species. Each LCST is dominated by one or two taxa that appear to represent keystone elements of an elaborate network of positive and negative interactions with minor components of the cheese microbiota. The results obtained in this study reveal the existence of peculiar cheese microbiota assemblies that represent intriguing targets for further functional studies aimed at dissecting the species-specific role of bacteria in cheese manufacturing.IMPORTANCE The microbiota is known to play a key role in the development of the organoleptic features of dairy products. Lactobacilli have been reported to represent one of the main components of the nonstarter bacterial population, i.e., bacteria that are not deliberately added to the milk, harbored by cheese, although the species-level composition of this microbial population has never been assessed in detail. In the present study, we applied a recently developed metagenomic approach that employs an internally transcribed spacer to profile the Lactobacillus population harbored by cheese produced from raw milk at the (sub)species level. The obtained data revealed the existence of particular Lactobacillus community state types consisting of clusters of Lactobacillus (sub)species that tend to cooccur in the screened cheeses. Moreover, analysis of covariances between members of this genus indicate that these taxa form an elaborate network of positive and negative interactions that define specific clusters of covariant lactobacilli.

Project description:BackgroundThe study of a production chain of raw milk cheeses (St Marcellin, Vercors area, France) led to the isolation of two Bifidobacterium populations: B. crudilactis and B. mongoliense, that were able to grow along the production chain. The aims of this study were to further detect and characterize these bacteria along the process and evaluate the ability of some strains to survive or grow in adverse conditions.ResultsUsing PCR coupled with restriction fragment length polymorphism, B. crudilactis and B. mongoliense were detected in respectively 77% and 30% of St Marcellin cheeses from production chain after 21 days of ripening. They were present in more than half of all analyzed retail cheeses with counts going from 1.6 to 5 log cfu g-1 for B. crudilactis and 1.4 to 7 log cfu g-1 for B. mongoliense. Bifidobacterium mongoliense was sensitive to pH 2, with an observed decrease of at least 3 log for both studied strains (FR49/f/2 and FR41/2) after 1 h incubation. At pH 3, no significant decrease was observed. Good survival was observed for the same strains in presence of pancreatic juice with a decrease of less than one log. Survival of strain FR49/f/2 was better than FR41/2 with a decrease of 3 logarithms (in presence of 1% bile salts) and almost 2 logarithms (in presence of 0.5% bile salts). The genotypic analyses using total DNA-DNA hybridization, GC% content, 16S rRNA gene sequencing and multilocus sequencing analysis (MLSA) confirmed the classification of Bifidobacterium. crudilactis and B. mongoliense into two different clusters well separated from other bifidobacteria clusters.ConclusionsAccording to the observed characteristics such as survival in adverse conditions and their ability to grow under 12 °C during the manufacturing process of the cheeses, which has never been described for bifidobacteria and which is a very interesting technological asset, these B. crudilactis and B. mongoliense strains should be further investigated for a potential use in new food or in food supplements.

Dataset Information

Characterization of the fungal microflora in raw milk and specialty cheeses of the province of Quebec.

Publications

Characterization of the fungal microflora in raw milk and specialty cheeses of the province of Quebec.

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