Wine acidity plays an important role in determining wine quality and ensuring physiochemical and microbiological
stability. In high-acid wines, the L-malic acid concentration is usually reduced through bacterial malolactic fermentation,
while acidulation in low-acidity wines is usually done during final blending of the wine before bottling.
This study showed that skin contact did not influence the relative concentration of L-malic acid in the pulp and juice
fractions from Colombard, Ruby Cabernet and Cabernet Sauvignon grape musts, with 32%-44% of the L-malic
acid present in the pulp fraction. Four recombinant malo-ethanolic (ME) Saccharomyces wine yeast strains containing
the malic enzyme (mae2) and malate transporter (mae1) genes of Schizosaccharomyces pombe, effectively
degraded the L-malic acid in both the juice and pulp fractions of all three cultivars, with a complete degradation of
malic acid in the juice fraction within 2 days.