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64 p r a c t i c a l w i n e r y & v i n e ya r d a U G U S t 2 0 1 4 nones. This will result in latent reactive phenolics capable of capturing and removing aromas and potentially caus- ing the wine to have an orange tinge or undergo pinking. The best option to eliminate phenolic compounds is the use of a specialized fining agent on the juice. This prevents formation of quinones during settling, while also pre- serving glutathione content in the must. 11 Glutathione reacts rapidly and needs to be exposed inside the yeast cell to enzyme glutathione reductase to be reactivated. Oxidation of glutathione is rapid in the presence of oxygen and oxygen-reactive compounds in non-reductive environ- ments outside the cell. Glutathione and glutathione precursor-containing prepa- rations are added to ferments to be taken up by yeast and kept internally in a proper redox state until autolysis and release for protective effect. Juice fining products include casein, PVPP and occasionally isinglass (fish fining agent). In recent years, concerns about aller- gen-free and organic products have led sup- pliers to develop alternative fining agents, and plant proteins were subsequently rec- ognized as the most viable option. The first plant-protein fining agents to be evaluated were extracted from wheat or peas. Due to allergy issues, wheat pro- teins did not provide an adequate solu- tion due to the presence of glutens, while the first pea proteins used presented an unacceptable odor, taste and sometimes susceptibility to oxidation. Enological demands have led suppliers to improve the quality of the pea protein products and potato proteins that have been evalu- ated and shown to be effective in all wine- fining applications including flotation. There are many choices for pea-based vegetal protein fining agents, both pure protein and blended products. Laffort has developed a proprietary protein fining agent extracted from potatoes, which is available under the trade name Vegecoll. 6 Depending on the final destination of the wine, animal protein-free, allergen- free and organic options exist, with all of them suitable for treatment of juice before fermentation. Yeast selection The choice of yeast strain can significantly influence the final aroma profile of white W I N E M A K I N G Figure 1. Formation of volatile phenols via the decarboxylation of hydroxycinnamic acids. 12 http://www.angelfire.com/ca5/RandDGlass Zambelli T/500 Wine or Must Pump Stainless steel pump head Stainless steel pump head, stainless steel faceplates with flexible impeller. Unit has variable speed motor capable of forward and backward operation. Also has 3" triclamp fittings and a stainless steel cart and a stainless steel cart. Pump speed (rpm) to 700, flow (gpm) to 200. Contact Us Today! 575 Third St., Bldg. A, Napa, CA 94559 Tel: (707) 255-6372; Fax: (707) 255-6462 www.napafermentation.com; wineyes@aol.com Napa Fermentation Supplies Napa Fermentation Supplies