Ethyl carbamate content in wines with malolactic fermentation induced at different points in the vinification process

Abstract

Ethyl carbamate (EC) is a carcinogenic compound found in fermented food and beverages such as wine. Although its carcinogenic potential in animals is known, information regarding its effects in humans remains insufficient, thus there is increasing interest in its research. EC content is higher in products with high alcohol content and in aged products. The main precursor involved in EC production in wine is urea, which is produced by metabolism of arginine by yeast, but there is also evidence that EC levels can increase after malolactic fermentation (MLF). Some lactic acid bacteria (LAB) can degrade the arginine present in must and wine via the arginine deiminase pathway, producing citrulline and carbamyl phosphate. Both compounds can react with ethanol in acidic conditions and produce EC. Our research group is studying the influence of MLF induced at different points of wine-making on the quality of the resulting wine. Among other parameters, the content of toxic compounds such as EC was evaluated. Results so far indicate that EC levels at the end of MLF were quite low (less than 3 μg/l) in all cases, i.e. below the existing legal limit (e.g. 30 μg/l in Canada). In almost all wines, EC concentrations increased after 8 months of storage as has been described by other authors. In some of the wines in which MLF was carried out by selected LAB, the increase in EC concentration was lower.

Evaluation of the antimicrobial activity of bacteriocin-like inhibitory substances of enological importance produced by Oenococcus oeni isolated from wine

“…cremoris [20] have also been found to produce some inhibitory compounds. However, all these are strains of malolactic bacteria involved in spontaneous processes, which entail a significant risk of wine spoilage through the overproduction of undesirable metabolites, such as acids, flavour compounds, acetaldehyde, biogenic amines, ethyl carbamate [21][22][23][24]. For a controlled, dynamic and safe malolactic process, Oenococcus oeni strains are therefore often advised in the wine industry.…”

The application of malolactic fermentation process to create good-quality grape wine produced in cool-climate countries: a review

“…Factors promoting the formation of these compounds include low pH, low alcohol content, and excessive keeping of wine over lees. This compound, although found naturally in many fermented products (alcoholic beverages, bread, cheese, yoghurts, sauerkraut), was classified by the European Parliament (C6-0267/2006) to be a class II carcinogen, next to, e.g., bromo ethylene or acrylamide [41,42]. A trend toward a reduction in admissible concentration threshold for this compound in food should be an incentive for the winemaking industry to apply techniques facilitating the inhibition of its biosynthesis.…”

“…Their depletion during alcoholic fermentation delays the onset of MLF up to the time of repeated increase in their concentration as a result of autolysis of yeast cells [8,21,58]. This in turn has to be closely controlled particularly due to the risk of excessive increase in urea concentration in wine-a precursor of carcinogenic urethane (ethyl carbamate) [41,42].…”

Improved sample preparation for GC–MS–SIM analysis of ethyl carbamate in wine

“…(1) addition of propyl carbamate as internal standard; (2) cleanup through diatomaceous earth columns; (3) EC extraction by dichloromethane, and (4) eluate concentration using vacuum rotary evaporation. This technique has been used by several authors (Masqué et al, 2011;Romero, Reguant, Bordons, & Masqué, 2009;Uthurry et al, 2004Uthurry et al, , 2006 for EC analysis in table wine in recent years. Limiting steps in the standard sample preparation procedures are: (1) use of considerable amounts of a chlorinated toxic solvent (dichloromethane) for extraction; (2) use of intensive labor effort and prolonged time during the concentration step, and (3) use of an internal standard with a lower degree of similarity to control extraction and chromatographic responses.…”