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70 practical winery & vineyard February 2015 w i n e m a k i n g KHT crystal growth? In Figure 3 an il- lustration of the size differential between a hydrogen atom and a potassium atom shows that potassium is much larger. In the crystal structures imagine KHT mol- ecules aligned in an end to end fashion, all lying nice and compact and flat at the crystal surface. The potassium molecules would be sticking up above the profile of the tartrate layer due to the larger di- ameter; this would act like a series of positively charged bumps all along the crystalline molecular surface. The attraction between the negatively charged CMC and the positive charges on the KHT crystal surface acts like Vel- cro, with a multitude of ionic interactions driving an association that is effectively permanent — in fact wine treated with CMC can exhibit long-term stability. 14 In addition to the physical performance properties that the DP and DS lend to CMC, physical properties that allow for low effective usage rates (100 ppm) and stability to temperature extremes need to be considered in product development. Purity of the CMC is important in re- spect to elimination of degradation that results in heterogeneity of molecular size and negative impact on performance. Re- fining of CMC to remove excess sodium after the initial production is important because sodium can impact the organo- leptic qualities of a wine. In development of a CMC product for use in wine tartrate stability treatment, parameters such as product color, chemi- cal impacts and organoleptic influence need to be considered. Since CMC is recommended for white and rosé wines, there should be no increase in A420 of white wines. Some less pure CMC can have a yellow color that is transferred to the wine upon treatment. The purpose of CMC treatment is not to modify the wine chemistry but simply provide KHT stability. Measurements of SO 2 , total acidity, pH, volatile acidity, eth- anol, NTU and color should all remain unchanged, thus preserving the wine balance intended by the winemaker. Organoleptic impacts from CMC use should be undetectable. These potential impacts include color changes, modi- fication of flavor-aroma profile and im- pacts on body, weight or mouthfeel of the treated wines, all of which can affect the perception of the wines. In specific trial applications, comparison of available tartrate stabilization methods showed differences in chemical effects and or- ganoleptic impacts. Not all CMC is the same in regard to DP, DS and functionality. As indicated by the diverse uses for CMC in many differ- ent food applications, the physical prop- erties of CMC can be altered through structural differences created by spe- cific production processes or refinement steps. Proper attention to the production and purification of the CMC raw mate- rial, followed by appropriate product formulation and handling, should allevi- ate concerns. Ask your supplier for details. The many different properties and applications of CMC are explained in depth at: codexalimentarius.net/gs- faonline/additives/details.html?id=51 Figure 4. Plot of Kht solubility versus temperature showing solubility and hypersolubility curves with resultant partitioning of Kht crystallization. 12