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48 W i n e s & V i n e s A P R i L 2 0 1 4 can be run by technicians trained to fol- low the procedures carefully. Malic acid The original, simple way to test for the completion of malolactic fermentation (ML) in a wine has been paper chromatog- raphy. There are many problems with this method of testing. First, most users of this test do not change the chromatography solutions often enough—once a week is recommended. Second, while the sensitiv- ity of the test is about 100ppm, completion of ML is defined as less than 30ppm. The most common way to assure that ML is complete is with an enzymatic test. Megazyme uses the same instrument used for glucose/fructose to measure malic acid, and this test follows the same proce- dures as with the glucose/fructose test. Megazyme's instrument is not a spectrom- eter. The company takes advantage of an enzymatic "trick" of taking the traditional end point that is measured at 340nm wavelength and converting it to one that measures in the visible light range of 520nm. This effect makes the instrument performing the analysis much less expen- sive to produce with nearly the same accuracy of a traditional spectrometer. The Randox Monza type of instrument provides a more precise analysis than either of the previous two procedures and is more useful for a wider variety of tests. Volatile acidity The traditional method of analyzing vola- tile acidity (VA) uses the cash still. This device extracts the volatile acids in wine using steam distillation. In addition to acetic acid and ethyl acetate, the main non-target acids this procedure also detects include CO 2 , SO 2 and sorbic acid. Lactic acid, proprionic acid and a few others also can contribute to the total volatile acid number. To the extent that all of these acids are present, techniques must be used to account for them so an artificially high value isn't reported for VA, especially if the VA level is approach- ing the legal limit. The cash still is a rather crude method for determining VA. Whereas one can account for the major contributors to the HoytShepston_Monthly09 10/31/08 4:44 PM Saracina Vineyards conducts wine analysis in this laboratory space. W I N E M A K I N G