A holistic approach of a mould cheese ripening is presented. The objective was to establish relationships between the different microbiological and biochemical changes during cheese ripening. Model cheeses were prepared from pasteurized milk inoculated with Kluyveromyces lactis, Geotrichum candidum, Penicillium camemberti and Brevibacterium linens under aseptic conditions. Two cheese-making trials with efficient control of environmental parameters were carried out and showed similar ripening characteristics. K. lactis grew rapidly between days 1 and 6 (generation time around 48 h). G. candidum grew exponentially between days 4 and 10 (generation time around 4 . 6 d). Brevi. linens also grew exponentially but after day 6 when Pen. camemberti mycelium began developing and the pH of the rind was close to 7. Its exponential growth presented 3 phases in relation to carbon and nitrogen substrate availability. Concentrations of Pen. camemberti mycelium were not followed by viable cell count but they were evaluated visually. The viable microorganism concentrations were well correlated with the carbon substrate concentrations in the core and in the rind. The lactose concentrations were negligible after 10 d ripening, and changes in lactate quantities were correlated with fungi flora. The pH of the inner part depended on NH 3 . Surface pH was significantly related to NH 3 concentration and to fungi growth. The acid-soluble nitrogen (ASN) and non-protein nitrogen (NPN) indexes and NH 3 concentrations of the rind were low until day 6, and then increased rapidly to follow the fungi concentrations until day 45. The ASN and NPN indexes and NH 3 concentrations in the core were lower than in the rind and they showed the same evolution. G. candidum and Pen. camemberti populations have a major effect on proteolysis ; nevertheless, K. lactis and Brevi. linens cell lysis also had an impact on proteolysis. Viable cell counts of K. lactis, G. candidum, Pen. camemberti and Brevi. linens were correlated with the environmental conditions, with proteolytic products and with carbon substrate assimilation. NH 3 diffusion from surface to the cheese core during ripening was highly suspected. Interaction phenomena between microorganisms are discussed.
Cheese ripening is a complex biochemical process driven by microbial communities composed of both eukaryotes and prokaryotes. Surface-ripened cheeses are widely consumed all over the world and are appreciated for their characteristic flavor. Microbial community composition has been studied for a long time on surface-ripened cheeses, but only limited knowledge has been acquired about its in situ metabolic activities. We applied metagenomic, metatranscriptomic and biochemical analyses to an experimental surface-ripened cheese composed of nine microbial species during four weeks of ripening. By combining all of the data, we were able to obtain an overview of the cheese maturation process and to better understand the metabolic activities of the different community members and their possible interactions. Furthermore, differential expression analysis was used to select a set of biomarker genes, providing a valuable tool that can be used to monitor the cheese-making process.
Experimental cheeses were prepared in triplicate from pasteurized milk inoculated with Debaryomyces hansenii under aseptic conditions. Three cheesemaking replicates, with efficient control of environmental parameters (temperature, relative humidity, atmospheric composition) showed similar ripening characteristics. Deb. hansenii grew only on the cheese surface, where its oxygen demand was satisfied, especially during the first 24 h (mean generation time, 5·8 h). Salting in a sterile saturated brine solution reduced its growth and decreased viability. Growth was slower after 48 h because of the decrease in ripening temperature (mean generation time, 94 h). The total count of Deb. hansenii was maximum (≈3×107 yeasts/mm2) after 6 d ripening and its viable cell concentration was ≈2×106cfu/mm2. This difference was due to the ‘non-viability’ of part of the population. The viable Deb. hansenii concentration was highly correlated (r2>0·95) with the lactate concentration in the inner part and with the surface and inner lactose concentrations, up to day 10 of ripening. This emphasized the importance of the diffusion of carbon substrate from the inner part to the surface of the cheese during ripening. The pH of the inner part depended significantly on the lactate and lactose concentrations. Surface pH was significantly related to inner lactate concentration, temperature and relative humidity. This also demonstrated the controlling role of carbon source diffusion.
Experimental cheeses inoculated with Debaryomyces hansenii and Brevibacterium linens were ripened for 76 d under aseptic conditions. Triplicate cheese-making trials were similar as a result of efficient control of the atmosphere. In all trials, D. hansenii grew rapidly during the first 2 d and then slowed, but growth remained exponential until d 10 (generation time around 70 h). Total cell counts were higher than the number of viable cells, and after 10 d they remained around 3 x 10(9) yeast/g of DM. This difference resulted from the nonviability of a fraction of D. hansenii. After d 15, the pH of the rind was close to 7, and B. linens grew exponentially until d 25 (generation time around 70 h). The growth rate subsequently decreased but remained exponential (generation time around 21 d). Cell counts of D. hansenii and B. linens were correlated with the environmental technical conditions. Total D. hansenii counts were also correlated with total B. linens counts. Viable B. linens counts were related to rind lactate, and total counts depended on rind pH, internal lactate, and D. hansenii viable counts. The internal pH of the cheese depended on lactate concentrations, whereas surface pH was related to internal lactose, temperature, and relative humidity. These results suggest a determining role of the diffusion of the carbon sources in the ripening of smear soft cheese.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.