Presentation on theme: "Wine Flavor Chemistry Flavor is the psychological interpretation of the physiological response to a physical stimulus Milton Bailey, University of Missouri,"— Presentation transcript:
Wine Flavor Chemistry Flavor is the psychological interpretation of the physiological response to a physical stimulus Milton Bailey, University of Missouri, 1986
2 -methoxy 3 isobutyl pyrazine (2 ppt) Identified in Bell Peppers (1969) Sensitive to light (1986) Method for quantifying : (2003) WHAT CAUSES VEGY FLAVOR in WINE?
Compounds released in white wines 4-mercapto-4-methylpentan-2-one (4MMP) (also in Scheurebe) 0.8 ng/l*; range 0-40 -- box tree, broom flower; cat pee; conifer 4-mercapto-4-methylpentan-2-ol (4MMPOH) 55 ng/l*; range 0-150 -- citrus zest; grapefruit 3-mercapto-3-methylbutan-1-ol (3MMB) 1,500 ng/l*; range 30-150 – cooked leeks 3-mercaptohexan-1-ol (3MH) 60 ng/l*; range 200-5,000 – grapefruit; passion fruit; passion fruit skin 3-mercaptohexylacetate (3MHA) (also in Merlot, Cabernet sauvignon) 4.2 ng/l*; range 0-500 – box tree; passion fruit; sweet sweaty Aqueous 12% alcohol solution with 5g/l tartaric acid; pH 3.5 25 J, triangle; 50% correct increases during fermentation as these potent thiols released from their S-cysteine conjugate precursors Markers for great Sauvignon blanc
Thiols in other varieties 4MMP and A3MH (3-mercaptohexylacetate [box tree]): Impact on aromas of Colombard and Muscat d’Alsace wines As well as on young wines from Petit manseng* 3MH Contributes passion fruit and grapefruit to Gewurtztraminer, Riesling, Petit manseng and botrytized Semillon * White variety, South West France – may be Albarino: floral fruity flavors, a distinct lemon and fruit salad flavor & high acidity increasing popularity in Languedoc & California Tominaga et al. (2000) AJEV 51(2):178-182
Production, location and extraction of S-Cysteine Conjugates Moderate water stress favor S-cysteine conjugate (P-thiol) formation; severe prolonged stress limits production Location of P-thiolsdiffer as f(volatile thiol) P-4MMP and P-4MMPOH -- 80% in juice P-3MH – 50:50 between juice and skin Upto 19 hours skin contact Some ↑ in P-4MMP and P-4MMPOH (20% + 30%) 50% ↑ in P-3MH (even more extracted if skin contact at 18C vs 10C) Peyrot des Gachons, Catherine: Aroma Potential of Sauvignon blanc grapes, PhD Dissertation Bordeaux
Transformation of p-thiols into varietal aromas Transformation % low (1 month after fermentation) – due to yeast lyases 1.4% for P-4MMP; 3% for P-4MMPOH; 4.2% for P-3MH Not much transformed? Or Lost? Or metabolized or unstable? – do not yet know Do know that P-thiol disappearance is correlated with thiol appearance Peyrot des Gachons, Catherine: Aroma Potential of Sauvignon blanc grapes, PhD Dissertation Bordeaux
Norisoprenoids/norterpenoids from carotenes Beta-damascenone Shiraz stalky, earthy, cigar, and tobacco aromas black pepper aroma by GCO not id’d Cabernet Sauvignon and Merlot dried fig, tobacco and chocolate aromas Zinfandel Preliminary studies: Not much contribution Glycosides in Red varieties
floral apple honey honey chocolate chocolate dried fig dried fig tobacco tobacco Base wine Napa Cabernet juice glycoside hydrolysate 0 1 2 3 4 Juice glycoside hydrolysate n=14 judges x 2 reps
Trellising or leaf removal increases light < 2-methoxy 3 isobutyl pyrazine > norisoprenoids Maturity How to assess pH, TA, °B? Grape Must Evaluation (evaluate in < 1 hour) Rinse and Crush grapes, add 20 ppm SO2 Homogenize skins/juice versus juice Grape Berry Evaluation Vineyard Variables:
Temperature: Cool: retain more volatiles Warmer: more esters but lose more (fruity) low MW Yeast strain:? Biggest issue is H2S production “Natural” versus inoculation Skin Contact Time/Cap Management Increase K, pH, phenols, anthocyanins Centrifuging? FERMENTATION
Terpene glycosides hydrolyze, but terpenes interconvert to less fruity forms Vitaspirane and 1,1,6 trimethyl 1,2 dihydronaphthalene increase Esters hydrolyze slowly: Acetate esters & higher MW faster. Acids esterify; pH ; Tannins polymerize Oxidation reactions AGING
Extraction of volatiles: vanillin, eugenol, oak lactone Extraction: phenols, acids, lignins, CHO Oak Aging
Oak aging continued VARIABLES: Source oak (Am Vanillin; Fr Phenols, extract) Sawn vs split Air vs kiln drying Air Vanillin; Kiln HMF Air drying in cool vs hot area Hot Vanillin,Oak lactone Hot vanilla, caramel, buttery Steamed or bent over fire Degree toasting Furfural, Vanillin
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