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WINEMAKING winemakers are daunted by the pros- pect of pushing a wine through ML. But malolactic has huge impacts on style and is thus tricky to use to reduce acid- ity without harming fruit aromas. Most other biological solutions also create byproducts that alter style, so biological de-acidification methods must be evalu- ated with extreme care. All saccharomyces cerevisiae yeasts con- sume some malic acid (generally around 10%) during primary fermentation with- out undesirable flavor production. Re- cently, strains like Lallemand's 71B have received favorable marks in reducing as much as one-third of malic acid. Pass the double salt Were it not for the fuss and bother it entails, double salt de-acidification would be the standard treatment to re- duce malic acid. It takes advantage of the precipitation of calcium malate that occurs at high pH. A portion of the juice (usually 20%–30%) is drawn off and treated with an excess of calcium car- bonate (CaCO3 ). The carbonate reacts with 100% of available protons, both free and bound, completely neutralizing the juice to pH 7.0, while the TA drops to zero. Under these conditions, calcium precipitates both tartrate (CaTa) and malate (CaMa) in proportion to what is present, as well as its namesake double salt (Ca2 TaMa). unlike conventional cold stabilization, membranes protect colloidal structure of the wine and save lots of energy. When recombined into the main lot, a wine with a TA of 10 g/L will be reduced to 7.0, with 30% of its buffer capacity re- moved. The wine can then be re-acidified with tartaric if needed, restoring acid bal- ance. The process does not create calcium instability because the final wine has only 30% calcium saturation. Sounds good. The only trouble is, be- solids—a slow, messy proposition. Cross- fore recombining the treated portion, it is essential to filter it to remove all crystals and excess CaCO3 , to say nothing of pulp flow clarification to the rescue. The new tangential-flow filters making appearances all over the country to replace DE filtra- tion seem tailor-made for double-salt fil- tration. Time to start sucking up to your neighbor who has one. Double salt must be done prior to malolactic, and preferably at the juice stage, due to the hazards of taking a wine to such a high pH even for a short time. Choose your weapon Cross-flow clarification is emblematic of a dizzying array of new membrane tech- nologies sweeping the wine world. Reverse osmosis (RO), an increasingly popular and available tool for removing rainwater from juice as well as for adjusting wine alcohol and VA content, has interesting prospects for de-acidification. Reverse osmosis membranes used in the wine industry are made of the same materials employed in conventional ster- ile filters, but with pore sizes 10,000 times tighter. While sterile filters attempt to remove only particulates, RO mem- branes retain all but the smallest dis- solved compounds. We rate RO filters according to the mo- lecular weight (MW) of a compound that QSEE US AT UNIFIED, BOOTH #F4 Wines & Vines JAnUARY 2012 141