The detailed analysis of the microbiome and resistome of artisanal blue-veined cheeses provides evidence on sources and patterns of succession linked with quality and safety traits.

BACKGROUND: Artisanal cheeses usually contain a highly diverse microbial community which can significantly impact their quality and safety. Here, we describe a detailed longitudinal study assessing the impact of ripening in three natural caves on the microbiome and resistome succession across three different producers of Cabrales blue-veined cheese. RESULTS: Both the producer and cave in which cheeses were ripened significantly influenced the cheese microbiome. Lactococcus and the former Lactobacillus genus, among other taxa, showed high abundance in cheeses at initial stages of ripening, either coming from the raw material, starter culture used, and/or the environment of processing plants. Along cheese ripening in caves, these taxa were displaced by other bacteria, such as Tetragenococcus, Corynebacterium, Brevibacterium, Yaniella, and Staphylococcus, predominantly originating from cave environments (mainly food contact surfaces), as demonstrated by source-tracking analysis, strain analysis at read level, and the characterization of 613 metagenome-assembled genomes. The high abundance of Tetragenococcus koreensis and Tetragenococcus halophilus detected in cheese has not been found previously in cheese metagenomes. Furthermore, Tetragenococcus showed a high level of horizontal gene transfer with other members of the cheese microbiome, mainly with Lactococcus and Staphylococcus, involving genes related to carbohydrate metabolism functions. The resistome analysis revealed that raw milk and the associated processing environments are a rich reservoir of antimicrobial resistance determinants, mainly associated with resistance to aminoglycosides, tetracyclines, and ß-lactam antibiotics and harbored by aerobic gram-negative bacteria of high relevance from a safety point of view, such as Escherichia coli, Salmonella enterica, Acinetobacter, and Klebsiella pneumoniae, and that the displacement of most raw milk-associated taxa by cave-associated taxa during ripening gave rise to a significant decrease in the load of ARGs and, therefore, to a safer end product. CONCLUSION: Overall, the cave environments represented an important source of non-starter microorganisms which may play a relevant role in the quality and safety of the end products. Among them, we have identified novel taxa and taxa not previously regarded as being dominant components of the cheese microbiome (Tetragenococcus spp.), providing very valuable information for the authentication of this protected designation of origin artisanal cheese. Video Abstract.

Analysis of volatile organic compounds in Irish rapeseed oils.

In recent years, consumer demand for health benefitting, pleasant-tasting rapeseed oil has increased, and so has production. Ireland's climate and agricultural background can support the production of high-quality rapeseed oil. Volatile organic compounds (VOC) can give rise to highly distinctive flavours in rapeseed oils, produced during crop growth and generated during processing. This study performed VOC and sensory evaluation to determine if correlations exist. Samples of Irish rapeseed oils from 6 different producers were analysed. Compounds detected in the oil samples consisted of acids, alcohols, aldehydes, ketones, benzenes, esters, ether, terpenes, and sulphurs. While variations in whole volatile profiles were not considered significant, individual compounds and volatile classes were for hexanal, pentanal, ketones, acids, and sulphurs compounds. Correlations were observed between the VOCs detected and the sensory profile, which indicated the VOC content may influence an oil's sensory profile.