Issue link: http://winesandvines.uberflip.com/i/62409
WINEMAKING protons and a sour taste, but the high pH means they aren't free and available. This can only happen if your protons are tied up somewhere. You have a lot of cops off duty, or in donut shops. In a typical case, a juice may have a TA of 10 g/L and a pH of 3.9. Normally in California, the culprit is a high amount of potassium and tartrate. Tartrate is not a very good donut shop, but it will do the job if there's enough around. In such a wine, we have lots of K+ simply acidify a sample of the juice to ex- actly pH 3.6. Now freeze the sample overnight (al- , lots of tartrate, so we might expect a big precipitation. But high tartrate will not readily form KHTa if the pH is too far above 3.6. The other way juice can have high pH and high TA is high malic acid. This hap- pens all too often in Europe and North America, but it is rare in California ex- cept during chilly years like 2010 and 2011, when it's anybody's guess. Since malic acid is not easily removed, the first step is to determine whether it's our prob- lem at all. Lab analysis for potassium and malate RWRefrigB&WAd.R2.10506.qxd 3/26/07 6:54 PM Page 1 To test for malic acid, use tartaric acid to bring a juice sample to pH 3.6 and freeze it overnight before running a TA test. is expensive and time consuming, but there's a simpler way. To test for this con- dition onsite, dissolve some tartaric acid in a small amount of warm water and R lowing for ice expansion), then thaw it out in the morning. Hopefully you'll see lots of white crystalline powder in the bottle. Either centrifuge, filter or settle out in the fridge, then run a TA. If the problem was high potassium, the resulting juice will have a big drop in TA to maybe around 8.5 g/L and a pH still at 3.6. If it works, go and do likewise to the big tank. If not, read on. Getting the bugs out Before we get on to high-tech membrane solutions, let's discuss biological solu- tions. Organisms that eat acid have great appeal to our inner cheapskate. I will only speak generally here, because yearly ad- vances in our knowledge promise to in- validate any specific information I might offer in this area. Historically, biological de-acidifica- R&D_Jan08 11/12/07 3:54 PM Page 1 tion has been fraught with hidden costs and dangers. Thanks to the beloved and recently deceased Ralph Kunkee's work at the University of California, Davis, in the 1970s, malolactic fermentation is a big success story, and today few Glass Apparatus for the Wine Laboratory Acclaimed by enologists across the continent! Industrial/Commercial Services R Winery Systems • Cold Storage • Process Cooling The R&D SO2 Apparatus uses the Aeration- Oxidation Method to maximize testing accuracy. It is specifically designed for this test in con- sultation with enologists. Flexible spherical joints and interchangeable flasks facilitate simple operation and minimize breakage. We manufacture a full line of wine laboratory equipment, and also provide Glassware Design Engineering, Custom Fabrication, and Repair Services. CALL, FAX OR WRITE FOR OUR CATALOG OF WINE APPARATUS. 707-766-8950 redwoodrefrig.com 140 Wines & Vines JAnUARY 2012 Research & Development Glass Products & Equipment, Inc. 1808 Harmon Street • Berkeley, CA • 510-547-6464 • Fax 510-547-3620 E-mail: RD1967@aol.com • Web site: http://go.to/RandD Suppliers of Lab Glassware to the Wine Industry since 1967 edwood efrigeration The RD80 Volatile Acid Still is an improvement on the Cash Still for determination of volatile acids in wine. It features an aspirator pump to remove the spent sample, which speeds testing, saves water, avoids repair bills, and prevents cross contamination of samples.