Laboratory tests on glycosidase preparations in wine

Abstract

The secondary glycosidasic activity of pectinase preparations is used to release flavour active compounds of wine. In order to identify any undesirable effects of other collateral enzymatic activities, laboratory tests were carried out using two commercial preparations: NOVAROM G (Novo-Nordisk) and AR 2000 (Gist-Brocades). A pool of wines was obtained by blending two white wines from neutral grapes (Chardonnay and Verdeca) and a red wine from aromatic grapes (Aleatico). The experiment was carried out by adding each enzymatic preparation to the sample and analysing, by gas chromatography, with flame ionisation and mass spectrometric detection, the free aroma compounds after 15 and 30 days. In the first 15 days, the glycosidasic activity of the NOVAROM G brought about a considerable increase in the wine’s free terpenic content, especially nerol, geraniol and citronellol. After 30 days, further increases in all terpenic compounds were observed. The AR 2000, after 15 days, brought about the release of a conspicuous amount of terpenes, more than the previous enzymatic preparation, which further increased after 30 days. Throughout the test period, the enzymatic preparation, NOVAROM G, had no effect on the content of the acetates of the higher alcohols, the compounds associated with the banana-pineapple (isoamyl acetate) and rose (2-phenyl ethyl acetate) scents. However, the AR 2000 brought about a rapid hydrolysis of total acetates, which caused a fifty percent reduction in isoamyl acetate after 15 days and continued to decline until, after 30 days, the remaining concentration was below the perception threshold. Neither of the enzymatic preparations, however, provoked significant effects on the ethyl esters of the fatty acids compared to the control wine. In addition, the AR 2000 revealed esterase activity involving fixed acids, such as malic acid and succinic acid, with a conspicuous formation of diethyl malate and diethyl succinate, which became more marked after 30 days.