Free amino acids and volatile compounds in vinegars obtained from different types of substrate

Abstract

The present work reports on the free amino acids and volatile compounds in vinegars obtained from different types of raw materials (cider, white wine and red wine). Based on the amino acid contents of three types of vinegar and of the substrates from which they were obtained, the profile of the nitrogensupplying compounds and their uptake for the acetic acid bacteria were very similar. The most important amino acid in terms of supply and uptake was found to be L-leucine. L-Proline proved also important in the wine vinegars, however it was not depleted as L-leucine. The different acetification reactions involved were found to yield acetoin, and plus 1,1-diethoxyethane in the wine vinegars.

Free amino acids, urea and ammonium ion contents for submerged wine vinegar production: influence of loading rate and air-flow rate

“…The increase in urea was especially interesting since this compound is known to be a precursor for ethylcarbamate. 4,14,15 Ethylcarbamate is a carcinogen typically found in fermented beverages; its formation should, therefore, be avoided as much as possible. To this end, it would be desirable, if at all possible, to use operating conditions that hinder the formation of urea.…”

“…[1][2][3] In this process, the bacteria use ethanol as a carbon and energy substrate and free amino acids and ammonium ion as main nitrogen sources. 4 The amino acids are also intermediates of other compounds that could influence product quality. Though AAB are able to synthetize amino acids from ammonium ion, a minimum presence of these compounds is desirable to facilitate their action.…”

“…[4][5][6] L-proline, L-methionine, L-leucine, L-ornithine and ammonium ion may together account for approximately 70% of the total nitrogen content in the wine 7 (mainly L-proline with approximately 40%). The high L-proline content can be explained by considering its high concentration in grape must, 4 as well as both the limitation of molecular oxygen during the alcoholic fermentation that prevents its degradation 6 and the fact that L-proline metabolized very little by yeast. 8 On the other hand, the presence of L-leucine can be explained by taking into account the fact that yeasts release this amino acid during alcoholic fermentation.…”

“…8 On the other hand, the presence of L-leucine can be explained by taking into account the fact that yeasts release this amino acid during alcoholic fermentation. 4 So far, the analysis of amino acid content has been applied to the characterization of wine vinegar, to study the chemical and biochemical transformations that take place during ageing, to explore the requirements of AAB strains for these compounds, and to study the differences in the pattern of amino acid consumption between surface and submerged acetifications. [9][10][11][12][13] Despite its importance for the process, the nitrogen source variation during acetic acid fermentation in wine is poorly documented.…”

“…Since urea is a precursor for ethyl carbamate, a carcinogenic compound found in fermented beverages, its production must be reduced as much as possible. 4,14,15 The present study was, therefore, carried out to examine the changes in free amino acids, urea and ammonium ion contents under different operational conditions for a semi-batch submerged wine vinegar production in order to evaluate the influence of two very important operational variables: loading rate and air-flow rate.…”