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Influence of cheese-making recipes on the composition and characteristics of Camembert-type cheese
Bloomy rind cheeses, including Camembert and related varieties, can he produced using alternative processes that vary based on milk preacidification, cutting, curd handling, and ripening parameters. Modification of these parameters creates distinct cheeses such as lactic curd, stabilized curd, and hybrids of the two. The objective of this study was to determine the influence of 5 Camembert-type cheese recipes on the composition and characteristics during ripening. Five varieties of Camembert-type cheese were produced: (1) lactic curd, (2) sweet curd, (3) washed curd, (4) solubilized curd, and (5) stabilized curd. Cheeses were aged at 13 degrees C for 10 d, during the mold growth phase, and 7 degrees C from d 11 until 50. Key quality metrics including texture development, pH (center and surface), and color were monitored throughout shelf-life. Compositional evaluation (d 5; fat, protein, moisture, salt, and minerals) grouped cheeses into 3 categories: (1) lactic curd, (2) sweet and washed curd, and (3) solubilized and stabilized curd. The lactic curd and stabilized curd were consistently the most different varieties for composition and quality metrics. Moisture content of Camembert-type varieties ranged from 53.15 to 57.99%, Ca ranged from 0.23 to 0.45%, and P ranged from 0.21 to 0.40%. All varieties followed the expected pH evolution on the rind and in the paste with the pH of the rind reaching 7 by d 10, and paste pH reaching 7 between 35 and 50 d. The displacement of the paste (distance traveled upon cutting) for the lactic curd was the greatest among the 5 varieties, reaching an average of 27 +/- 1.9 mm (mean +/- standard error) after 50 d of ripening and 60 min of flow time. The stabilized curd on the other hand traveled the shortest distance, reaching an average of 4 +/- 0.4 mm at the same time point. Browning, considered a defect in mold-ripened cheeses, was observed in all varieties, but was most substantial for lactic curd (lightness, L*, decreased from 87.19 to 68.58). Based on these quality metrics the shelf-life of these recipes was estimated with the lactic curd having the shortest, and the stabilized curd having the longest. Examining Camembert-type cheese quality metrics for these 5 varieties can assist cheesemakers during recipe formulation and selection of cheese-making practices to achieve optimum product quality
Application of Whole Genome Sequencing to Understand Diversity and Presence of Genes Associated with Sanitizer Tolerance in Listeria monocytogenes from Produce Handling Sources
Recent listeriosis outbreaks linked to fresh produce suggest the need to better understand and mitigate L. monocytogenes contamination in packing and processing environments. Using whole genome sequencing (WGS) and phenotype screening assays for sanitizer tolerance, we characterized 48 L. monocytogenes isolates previously recovered from environmental samples in five produce handling facilities. Within the studied population there were 10 sequence types (STs) and 16 cgMLST types (CTs). Pairwise single nucleotide polymorphisms (SNPs) ranged from 0 to 3047 SNPs within a CT, revealing closely and distantly related isolates indicative of both sporadic and continuous contamination events within the facility. Within Facility 1, we identified a closely related cluster (0–2 SNPs) of isolates belonging to clonal complex 37 (CC37; CT9492), with isolates recovered during sampling events 1-year apart and in various locations inside and outside the facility. The accessory genome of these CC37 isolates varied from 94 to 210 genes. Notable genetic elements and mutations amongst the isolates included the bcrABC cassette (2/48), associated with QAC tolerance; mutations in the actA gene on the Listeria pathogenicity island (LIPI) 1 (20/48); presence of LIPI-3 (21/48) and LIPI-4 (23/48). This work highlights the potential use of WGS in tracing the pathogen within a facility and understanding properties of L. monocytogenes in produce settings