Microbiology of Cheddar cheese made with different fat contents using a Lactococcus lactis single-strain starter

Abstract

Flavor development in low-fat Cheddar cheese is typified by delayed or muted evolution of desirable flavor and aroma, and a propensity to acquire undesirable meaty-brothy or burnt-brothy off-flavor notes early in ripening. The biochemical basis for these flavor deficiencies is unclear, but flavor production in bacterial-ripened cheese is known to rely on microorganisms and enzymes present in the cheese matrix. Lipid removal fundamentally alters cheese composition, which can modify the cheese microenvironment in ways that may affect growth and enzymatic activity of starter or nonstarter lactic acid bacteria (NSLAB). Additionally, manufacture of low-fat cheeses often involves changes to processing protocols that may substantially alter cheese redox potential, salt-in-moisture content, acid content, water activity, or pH. However, the consequences of these changes on microbial ecology and metabolism remain obscure. The objective of this study was to investigate the influence of fat content on population dynamics of starter bacteria and NSLAB over 9 mo of aging. Duplicate vats of full fat, 50% reduced-fat, and low-fat (containing <6% fat) Cheddar cheeses were manufactured at 3 different locations with a single-strain Lactococcus lactis starter culture using standardized procedures. Cheeses were ripened at 8°C and sampled periodically for microbiological attributes. Microbiological counts indicated that initial populations of nonstarter bacteria were much lower in full-fat compared with low-fat cheeses made at all 3 sites, and starter viability also declined at a more rapid rate during ripening in full-fat compared with 50% reduced-fat and low-fat cheeses. Denaturing gradient gel electrophoresis of cheese bacteria showed that the NSLAB fraction of all cheeses was dominated by Lactobacillus curvatus, but a few other species of bacteria were sporadically detected. Thus, changes in fat level were correlated with populations of different bacteria, but did not appear to alter the predominant types of bacteria in the cheese.

Application of ARISA to assess the influence of salt content and cation type on microbiological diversity of Cheddar cheese

“…; Broadbent et al . ). Thus, ARISA will be able to detect NSLAB present in Cheddar cheese during the entire ripening.…”

“…As we have previously described (Broadbent et al . ), incubations at 10°C were used to capture microbial species that are able to grow or persist in cheese ripened at 8°C. Enrichment on nonselective agar at 30 or 45°C allowed us to collect species that either may not grow in cheese or are present at very low numbers in the matrix.…”

“…The finding that ARISA profile from cheese extracts incubated at 45°C was considerably more diverse than that obtained at 10 or 30°C is in agreement with a previous DGGE‐based study (Broadbent et al . ) and is likely due to that fact that enrichment at 45°C on nonselective agar affords an opportunity for outgrowth of bacterial spores and bacterial species that either may not grow in cheese or are present at very low numbers in the matrix.…”

“…DGGE analysis was performed with the CBS Scientific Company (Solana Beach, CA) DGGE system according to the protocol described by Broadbent et al . (). Bands that were prominent, unique to the sample, or changed in intensity (i.e.…”

Potential of Lactobacillus curvatus LFC1 to produce slits in Cheddar cheese

“…We have chosen to focus on Lb. curvatus LFC1, as the prevalence of this organism in Cheddar cheese has been increasing (Broadbent et al, 2013;Porcellato et al, 2014;Somers et al, 2001) and as preliminary cheese trials (Johnson M.E., unpublished data) correlated the addition of this organism with the development of undesired gas defects in Cheddar cheese.…”