Undesirable compounds and spoilage microorganisms in wine

Abstract

Ethyl carbamate (EC) and biogenic amines (BA) are the only wine compounds of microbial origin with undesirable effects on health. In excessive concentrations, the former is said to be carcinogenic and the latter may induce allergenic-like effects. EC is produced by the reaction of ethanol with urea and, to a very minor extent, citrulline, resulting from the arginine metabolism, by yeast and lactic acid bacteria (LAB), respectively. All Saccharomyces strains produce variable amounts of urea and the final concentration depends on the nitrogen nutrition and the prevailing conditions during alcoholic fermentation. All heterofermentative lactobacilli produce citrulline, but only some strains of Oenococcus oeni do so. BA are produced by only those LAB strains which are able to decarboxylate or deaminate amino acids. The arginine-degrading strains and BA-producing bacteria are characterized by gene clusters which are either stable or not in the genome. Environmental factors concerning the increasing risks of EC and BA accumulation have been identified, including viticultural and enological practices. Based on these findings, recommendations have been made in order to minimize the problem. There are limits for EC concentration, but, in table wines, concentrations are generally below this threshold. There is no regulation concerning BA, as its undesirable effects have not been conclusively demonstrated and remain controversial.