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W i n e s & V i n e s A P R i L 2 0 1 4 47 It is important to measure fermentable nitrogen and not just add diammonium phosphate (DAP) proactively. Amounts exceeding 500 ppm can lead to the forma- tion of carcinogenic compounds such as carbamate in the wine. These compounds are regulated by many jurisdictions including Canada and the European Union for wines imported into those countries, and limits are also set by TTB for United States wine sales. Heat stability Heat stability is a test that is absolutely important. There are two ways to conduct this test: the right way and the other way. Too many winemakers gamble with phys- ics and hope that a wine will sell before there is a haze caused by unstable proteins. As an analogy, it isn't a case of whether an egg left at room temperature will have the albumin (egg white) solidify, but a case of when it will solidify. The same is true with unstable proteins in wine. One of the important devices for a win- ery laboratory is a nephelometer. This device measures turbidity of a liquid. You can spend a lot of money for a nephelom- eter, but the one sold by Hanna is a good value for the money. The test for unstable protein is simple. Filter a wine to 0.45µ and then place in boiling water for 10 minutes. A wine is heat stable if the beginning turbidity com- plies with the ending turbidity using a formula. The formula I use is X=T 2 -(T 1 /2) and the wine is stable when X is less than five. If the result is greater than five, the wine is not stable and bentonite must be added to correct the problem. The other way is to let your eye deter- mine heat stability. I have found through hard experience that the eye is not as good as a nephelometer. Cold stability Cold stability measures the degree to which tartaric acid is in supersaturation in the wine. As in heat stability, it is a sim- ple test but not as easy to conduct. The easiest test, and one that is fairly rigorous, is to freeze a sample in a regular freezer for precisely 12 hours. To the degree that there are no crystals at the bottom, the wine is cold stable. As with the heat sta- bility test indicated above, evaluating the test result using your eyes can lead to an erroneous conclusion. This method is highly subjective, especially at the mar- gins of cold stability. There are several ways to set up a rou- tine test environment that is much more accurate than looking for crystals with your eyes. The instrument of choice is a conductivity meter, which is a relatively inexpensive meter that evaluates cold sta- bility reasonably accurately. Procedurally, the steps that are required involve chilling a wine to 28 o F, dropping in cream of tartar and then measuring the fall in conductivity. If the fall is less than 5% of the initial reading, your wine is cold stable. To run this test, one needs to make a reservoir that can use the winery's existing glycol system and hold a liter of wine at 28 o F. Then add the cream of tar- tar. Keep the temperature within 0.5 o of at 28 o F during the test. This will make a good approximation of cold stability to about 95% + assurance that it has achieved cold stability. For greater accuracy (at a cost of about $12,000 to $15,000) you can get a system from Ameridia or Alpine Scientific that uses a commercial glycol unit and a com- puter formula to calculate the conductiv- ity drop to infinity. In 15 to 20 minutes, the program projects conductivity so that there is a virtual guarantee of cold stability. Glucose fructose Megazyme has developed a simple meter that can take the place of a spec- trometer to measure malic acid and glu- cose fructose. This hand-held device has a simplified pipetting method that is easier to use than a full-blown spectro- photometer. The same 20µl pipette is used for all the small additions. If you are stepping into more sophisticated analysis, this several hundred dollar instrument will allow these two enzy- matic analysis to be conducted. However, if a winery wants to expand the laboratory into a more self-sustaining unit, it would be wise to consider the Randox Monza or similar instrument since this test is just one of many that this type of instrument can analyze. While the steps for each of these instruments are slightly different, this type of instrument Highlights • Integrity of the packaged product is essential to maintaining a winery's reputation. • Wineries can perform low-cost versions of heat and cold stability tests on- site, although equipment offers more precise results. • A hand-held device is now available to measure malic acid and glucose fructose. Hanna Instruments' titrator measures the levels of acidity in wine samples. Randox Monza offers routine chemistry analysis such as glucose/fructose. The Stabilab by Oenodia is a tartaric precipi- tation analyzer. View VIdeo: This video from Yakima Valley Community College shows how to measure titratable acidity in wine or grape juice. W I N E M A K I N G