The effect of organic acids and sulphur dioxide on C4 compounds production and β-glycosidase activity of Oenococcus oeni from wines under acid conditions. International Journal of Wine Research. En prensa. Maturano C. y Saguir F.M

MATURANO CARMEN; SAGUIR, FABIANA MARíA; RODRIGUEZ VAQUERO MARIA JOSé; RIVERO LUCIANA

International Journal of Wine Research

Dove Press

Año: 2016 vol. 8 p. 19 - 28

1179-1403

The purpose of this work was to investigate the effect of L-malic and citric acids and/or SO2 on two biochemical properties (diacetyl/acetoin/2,3-butanediol formation and -glucosidase activity) relevant to flavor development in six Oenococcus oeni strains from wines at pH 4.8 and 3.8. Cells were cultured in MRS without citrate (CM) and added with L-malic (2 g/l) and citric (0.7 g/l) acids and/or SO2 (80 mg/l) at pH 4.8 and 3.8. All test strains grew at all conditions tested including in SO2 presence and at initial pH 3.8, even though growth parameters were maximum in presence of both acids at pH 4.8. Organic acids were depleted totally regardless of condition examined, occurring L-malic acid degradation faster than citric acid. Diacetyl, acetoin and 2,3-butanediol levels significantly varied depending on strain for a given condition, e.g. at pH 4.8 in CM the highest value (6.55±0.31 mg/l, strain MS25) represented almost 3-fold the positive lowest one (2.43±0.22 mg/l, strain MS9). There was also variability for each strain depending on initial pH (strains MS25, MS27, MS48) and organic acids presence (all strains except MS25) but not SO2. In addition, among strains there was a trend towards mainly diacetyl formation (55-75%). O. oeni MS9, MS20 and MS46 yielding adequate diacetyl levels were selected for investigating specific -glucosidase activity and its possible cell localization. Cell suspensions of all strains selected exhibited positive activities at both pH values being higher at 4.8. As observed for C4 compounds, organic acids stimulated this activity (28-49 % at pH 4.8; ~20% at pH 3.8), thus partially reverting the inhibition caused by acid stress while SO2 did not affect it. Use of different cell fractions (permeabilized cells, protoplasts, cell extracts) associated this activity to cell surface. Results indicated that diacetyl formation and β-glucosidase activity levels in O. oeni strains as influenced by acidity and organic acids are of relevance for vinification decisions.