Lactobacillus demonstrate thiol-independent metabolism of methylglyoxal: Implications toward browning prevention in Parmesan cheese

Endogenous production of α-dicarbonyls by lactic acid bacteria can influence the quality and consistency of fermented foods and beverages. Methylglyoxal (MG) in Parmesan cheese can contribute toward undesired browning during low temperature ripening and storage conditions, leading to the economic de...

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Bibliographic Details
Published in:	Journal of dairy science Vol. 101; no. 2; p. 968
Main Authors:	Gandhi, N N, Cobra, P F, Steele, J L, Markley, J L, Rankin, S A
Format:	Journal Article
Language:	English
Published:	United States 01-02-2018
Subjects:	Cheese - analysis Color Diacetyl - analysis Fermentation Glyoxal - analysis Lactobacillus - genetics Lactobacillus - metabolism Pyruvaldehyde - administration & dosage Pyruvaldehyde - analysis Pyruvaldehyde - metabolism Sulfhydryl Compounds - metabolism Volatile Organic Compounds - analysis Parmesan cheese browning methylglyoxal α-dicarbonyl Lactobacillus
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Summary:	Endogenous production of α-dicarbonyls by lactic acid bacteria can influence the quality and consistency of fermented foods and beverages. Methylglyoxal (MG) in Parmesan cheese can contribute toward undesired browning during low temperature ripening and storage conditions, leading to the economic depreciation of affected cheeses. We demonstrate the effects of exogenously added MG on browning and volatile formation using a Parmesan cheese extract (PCE). To determine the influence of Lactobacillus on α-dicarbonyls, strains were screened for their ability to modulate concentrations of MG, glyoxal, and diacetyl in PCE. It was found that a major metabolic pathway of MG in Lactobacillus is a thiol-independent reduction, whereby MG is partially or fully reduced to acetol and 1,2-propanediol, respectively. The majority of lactobacilli grown in PCE accumulated the intermediate acetol, whereas Lactobacillus brevis 367 formed exclusively 1,2-propanediol and Lactobacillus fermentum 14931 formed both metabolites. In addition, we determined the inherent tolerance to bacteriostatic concentrations of MG among lactobacilli grown in rich media. It was found that L. brevis 367 reduces MG exclusively to 1,2-propanediol, which correlates to both its ability to significantly decrease MG concentrations in PCE, as well as its significantly higher tolerance to MG, in comparison to other lactobacilli screened. These findings have broader implications toward lactobacilli as a viable solution for reducing MG-mediated browning of Parmesan cheese.
ISSN:	1525-3198
DOI:	10.3168/jds.2017-13577