The effect of organic acids and sulphur dioxide on C4 compounds production and â-glycosidase activity of Oenococcus oeni from wines under acid conditions

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

International Journal of Wine Research

Dove Press

Año: 2016 vol. 8 p. 19 - 28

1179-1403

The purposeof this work was to investigate the effect of L-malic and citric acids and/or SO2on two biochemical properties(diacetyl/acetoin/2,3-butanediolformation and b-glucosidaseactivity) relevant to flavor development insix Oenococcus oeni strains fromwines at pH 4.8 and 3.8. Cells were cultured in MRS without citrate (CM) andadded with L-malic (2 g/l) and citric (0.7 g/l) acids and/or SO2 (80mg/l) at pH 4.8 and 3.8. All test strains grew at all conditions testedincluding in SO2 presence and at initial pH 3.8, even though growthparameters were maximum in presence of both acids at pH 4.8. Organic acids weredepleted totally regardless of condition examined, occurring L-malic aciddegradation faster than citric acid. Diacetyl, acetoin and 2,3-butanediollevels significantly varied depending on strain for a given condition, e.g. atpH 4.8 in CM the highest value (6.55±0.31 mg/l, strain MS25) represented almost3-fold the positive lowest one (2.43±0.22 mg/l, strain MS9). There was also variabilityfor each strain depending on initial pH (strains MS25, MS27, MS48) and organicacids 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 andMS46 yielding adequate diacetyl levels were selected forinvestigating specific b-glucosidase activity and itspossible cell localization. Cell suspensions of all strains selected exhibited positive activities atboth pH values being higher at 4.8. As observed for C4 compounds, organic acidsstimulated this activity (28-49 % at pH 4.8; ~20% at pH 3.8), thus partiallyreverting the inhibition caused by acid stress while SO2 did notaffect it. Use of different cell fractions (permeabilizedcells, protoplasts, cell extracts) associated this activity to cellsurface. Results indicated that diacetyl formation and â-glucosidase activitylevels in O. oeni strains asinfluenced by acidity and organic acids are of relevance for vinificationdecisions.