5/17/2017 UC DAVIS VITICULTURE AND ENOLOGY FLORAL AND FRUITY TAINTS ANITA OBERHOLSTER MAY 18, 2017 Wine Flavor 101: Recognizing Non-Microbial Taints UC DAVIS VITICULTURE AND ENOLOGY Outline • Origin • Formation • Characteristics • Influences 1 5/17/2017 UC DAVIS VITICULTURE AND ENOLOGY Introduction • Floral/Fruity taints • Responsible compounds present in many varietals • Become a taint/problem when: • Too dominant in the aroma profile: loss of complexity • Present in high enough concentration to obtain a different negative aroma characteristic • Expressed in varietal where normally below threshold of detection/not acceptable to consumer UC DAVIS VITICULTURE AND ENOLOGY Origin • Grape-derived – can provide varietal distinction • Monoterpenes • Phenylpropanoids 2 5/17/2017 UC DAVIS VITICULTURE AND ENOLOGY Monoterpenes • Formed through 2 potential biochemical pathways (MVA or MEP) • Important contributors to aroma of Muscat varieties • Muscat of Alexandria, Muscat de Frontignan • Aromatic non-Muscat varieties • Gewürztraminer, Riesling • High corr floral aroma and high [linalool] and [-terpineol] UC DAVIS VITICULTURE AND ENOLOGY Monoterpenes • High conc of linalool and -terpineol = floral, citrus, rose, lilac aromas • Odor thresholds (μg/L) is 50 for linalool and 78 for -terpineol linalool -terpineol 3 5/17/2017 UC DAVIS VITICULTURE AND ENOLOGY Monoterpenes • (Z)-rose-oxide important aroma in Gewürztraminer = lychee aroma, although generally described as green vegetable, floral, geranium, camphoreous with spicy nuance • Odor threshold (μg/L) is 0.2 (Z)-rose oxide UC DAVIS VITICULTURE AND ENOLOGY Monoterpenoid • Citronellol = floral, leathery, waxy, rose citrus • Odor thresholds (μg/L) is 18 Citronellol 4 5/17/2017 UC DAVIS VITICULTURE AND ENOLOGY Monoterpenoid • Geraniol = sweet, floral, fruity, rose , waxy, citrus • Odor thresholds (μg/L) is 130 Geraniol UC DAVIS VITICULTURE AND ENOLOGY Monoterpenes in white wines 5 5/17/2017 UC DAVIS VITICULTURE AND ENOLOGY Monoterpenes • Red varieties not phenotypically characterised by high levels of terpenes • Low levels of linalool, citronellol, neorl and geranyl/neryl acetone in Cab Sauv grapes (<1.5 ug/kg) UC DAVIS VITICULTURE AND ENOLOGY Formation of terpenes • Grape Biosynthesise through isoprene/terpene metabolism • Monoterpenes also subject to pH and temp transformation in juice and wine • For ex. under acidic conditions geraniol and linalool degrade to linalool oxides and - terpineol • More prevalent at high temp as during storage and transport – result in aged characters 6 5/17/2017 UC DAVIS VITICULTURE AND ENOLOGY Formation of terpenes • Monoterpenes can also result from non- grape materials • E.g., 1,8-cineole (eucalyptol) • Synthesize in Cab Sauv berries after set • Also originate from eucalyptus trees in and around vineyards • Eucalyptus and minty aromas • Consumer rejection threshold 27.2 μg/L UC DAVIS VITICULTURE AND ENOLOGY Formation of terpenes • 1,8-cineole (eucalyptol) • Synthesize in Cab Sauv berries after set 7 5/17/2017 UC DAVIS VITICULTURE AND ENOLOGY Environmental influences • Exposure to sunlight favors accumulation of monoterpenes • Can be factor of temp and light exposure on enzyme activity within the fruit • Both canopy management and water stress can manipulate fruit light interception • Crop thinning has shown to ↑glycosylated terpenes UC DAVIS VITICULTURE AND ENOLOGY Environmental influences • Grape maturity • Increase in monoterpenes with sugar accumulation • Consistent with up-regulation of genes involved in early stages of terpene synthesis during maturation 8 5/17/2017 UC DAVIS VITICULTURE AND ENOLOGY Environmental influences • Fungal infections • E.g. B. cinerea causing gray bunch rot can transform monoterpenes • Novel polyfunctional thiol cysteine conjugates were identified in botrytis-infected Sauv blanc, Semillon – contribute to unique flavour of botrytized sweet wines UC DAVIS VITICULTURE AND ENOLOGY Sesquiterpenes • Rotundone • Characteristic pepper aroma in Vitis vinifera cv. Shiraz 9 5/17/2017 UC DAVIS VITICULTURE AND ENOLOGY Phenylpropanoids • Not much known about biosynthetic pathways leading to formation in grapes • Methyl anthranilate • Responsible for ‘foxy’ aroma and flavor in Concord grapes (Vitis labrusca) • May also contribute to Pinot noir aroma • Used as main grape flavor compound in food • May also be present in wine through external sources • Oak (Quercus sp.) barrels used for fermentation and aging • Smoke event in the vineyard UC DAVIS VITICULTURE AND ENOLOGY Phenylpropanoids • Methyl anthranilate is also an ester • Few esters formed in grapes • Esters characteristic of fruity floral aromas • Enzymatic esterification in the grape • Esters in wine have mainly two origins • Enzymatic esterification during fermentation • Chemical esterification during long-term storage • Some esters are synthesized by yeast from grape precursors • Can be variety depended 10 5/17/2017 UC DAVIS VITICULTURE AND ENOLOGY Phenylpropanoids - esters • For example in Pinot noir characteristic aromas • Plum, strawberry, raspberry, blackcurrant and blackberry influenced by 4 esters Ethyl anthranilate Methyl anthranilate (sweet‐fruity, grape‐like odor) UC DAVIS VITICULTURE AND ENOLOGY Phenylpropanoids - esters • For example in Pinot noir characteristic aromas • Plum, strawberry, raspberry, blackcurrant and blackberry influenced by 4 esters Ethyl cinnamate 2,3‐dihydrocinnamate (cinnamonlike, sweet‐balsamic, sweet‐fruity, plum, cherry) 11 5/17/2017 UC DAVIS VITICULTURE AND ENOLOGY Phenylpropanoids - esters • Another related compound is Ethyl Phenylpropionate • Hyacinth, rose, honey, fruit rum aroma Ethyl Phenylpropionate (ethyl 2,3-dihydrocinnamate) UC DAVIS VITICULTURE AND ENOLOGY Ester • Methyl Benzoate • Orange, floral, chemical with a phenolic and cherry pit note Methyl benzoate 12 5/17/2017 UC DAVIS VITICULTURE AND ENOLOGY To conclude • Floral and fruity taints • Floral and fruity aromas mostly increase with ripeness and sun exposure • Mostly present in grape skins • At low conc contribute positively to wine aroma • High conc can make wine one-dimensional • Very high conc seen as a taint by some • If vineyard block known to be problematic • Adjust canopy management and picking time • Adjust skin contact time and fermentation temp during winemaking 13.