HPLC determination of amino acids with AQC derivatization in vinegars along submerged and surface acetifications and its relation to the microbiota

The present paper reports the determination of 22 amino acids and ammonium along the acetification process by high-performance liquid chromatography (HPLC), employing 6-aminoquinolyl-N-hydrosysuccinimidyl carbamate (AQC) as precolumn derivatization reagent. The method was successfully validated obtaining adequate values to selectivity, response linearity, precision and accuracy, as well as low detection and quantification limits. Its utility for routine analysis of amino acids along acetification has been proved. Three red wine substrates were fermented employing two kinds of acetification methods (surfaced and submerged culture) and the requirements of amino acids and ammonium as nitrogen source by acetic acid bacteria were evaluated. The identification of the acetic acid bacteria at species level was also done. At the beginning, the principal amino acid, in terms of abundance, was proline followed by arginine. A different behavior between both the acetification methods was observed. First of all, the consumption of amino acids is much lower in submerged than in surface acetifications. For surface culture acetification, the most consumed was proline, arginine being the main nitrogen source for submerged acetification systems. On the other hand, it was also observed that the nitrogen requirement of the bacteria is proportional to the time spent in the acetification process.