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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 69 sotolon and phenyl acetaldehyde. 9 The addition of pure glutathione to fin- ished wine, however, is not legally per- mitted. There are several yeast-derived products available that could increase a wine's glutathione level. These yeast- derived products are rich in glutathione and the precursors for glutathione pro- duction including cysteine and N-acetyl- cysteine. The potential to enhance the final wine depends on the original gluta- thione content and composition of the wine after primary fermentation and handling of the wine from a redox per- spective. Addition of these products as nutri- tional aids during the first third of pri- mary fermentation are legal and assist the yeast internal redox balance and enhances the final glutathione content of wines and, as a result, increases the sta- bility of the volatile thiols and thus the longevity of a wine. Autolyzed yeast nutritional aids are allowed by TTB Reg- ulation 27 CFR 24.246 —Materials autho- rized for the treatment of wine and juice. Conclusions Winemaking consists of a series of steps. Each step requires a calculated decision by the winemaker. A good winemaker makes informed decisions and takes the neces- sary precautions to protect and possibly enhance the quality delivered to him/her from the vineyard. Various winemaking practices influence white wine aroma. In the pursuit of quality aromatic white wines, decisions regarding the extraction of positive flavor-aroma character from the incoming grapes must be balanced with the possibility of over extraction and obtaining undesirable components. Greater extrac- tion of the must by several mechanisms— including proper enzyme selection and use, followed by removal of excess phenolics by selective juice fining, can allow for more positive flavor-aroma compounds. Enhancement of the flavor-aroma char- acter through proper yeast strain selec- tion, rehydration product addition and fermentation nutrition protocols can add significantly to the flavor-aroma profile of a white aromatic wine in both com- plexity and volume. The extraction and enhancement of w h i t e a ro m a t i c w i n e f l a v o r- a ro m a must be followed with a strategy for preservation of the gains accomplished t h ro u g h p ro p e r d e c i s i o n m a k i n g . Many processing decisions made by the winemaker will impact the delicate flavor-aroma compounds and oxida- tion is the true enemy of these critical molecules. Understanding oxidation-reduction reactions that can occur in wine and the treatments available to assist in anti-oxi- dation are keys to making expressive aro- matic white wines that will deliver their potential to the wine enthusiast upon consumption. 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Figure 6. A comparison of the glutathione con- tent and total reductive power of six different commercial products.