VWT 272 Class 14. Quiz 12. Number of quizzes taken 16 Min 3 Max 30 Mean 21.1 Median 21 Mode 23

Transcription

1 VWT 272 Class 14 Quiz 12 Number of quizzes taken 16 Min 3 Max 30 Mean 21.1 Median 21 Mode 23

2 Lecture 14 Phenolics: The Dark Art of Winemaking Whether at Naishapur or Babylon, Whether the Cup with sweet or bitter run, The Wine of Life keeps oozing drop by drop, The Leaves of Life keep falling one by one. Omar Khayyam ( )

3 Plan of Study Phenolics Grape Flavonoids Non-Flavonoids Copigmentation Phenolics Wood Non-Flavoniods Phenolics and Wine Ageing Color stability Volatile Phenols

4 An (Economics) Joke Alfred Marshal ( ) British Founder of Neoclassical Economics Professor of Political Economy at Cambridge University

5 Phenolic Compounds Phenol Not found in grapes Not found in wine

6 Phenolic Compounds - Source Produced by plants Grapes Seeds 70 % to 85 % of grape phenolics Pulp?? % Teinturier» Rubired & Alacante Bouschet Skins 15 % to 30 % of grape phenolics Increase as berry matures Varies with» Vintage» Increasing Sunlight» Increasing Temperature (?) Defense mechanism Sun screen

7 Phenolic Compounds - Types Produced by Grapes Flavonoid Phenolics Anthocyanins From the Greek anthos (flower) + kyanos (blue) Flavorless & odorless Increase after véraison Major source of (initial) color in wine Hue is dependant on ph» Low = RED High = BLUE Visual density is dependant on concentration» Low = LIGHT High = DARK

8 Phenolic Compounds - Types Produced by Grapes Flavonoid Phenolics Anthocyanins (continued) In grape skins 5 types found in grapes & wines» Malvidin-3-glucoside (red) Grenache ~90% Sangiovese ~50%

9 Phenolic Compounds - Types Produced by Grapes Flavonoid Phenolics Anthocyanins (continued) Cold Soak??? In fermentation extraction from must» Increases with time» Increases with temperature» Increases with alcohol concentration Range from 200 to 2000 mg/l Not stable Copigmentation with flavonols Adsorb to yeast cell walls Precipitate with tartaric acid salts

10 Phenolic Compounds - Types Produced by Grapes Flavonoid Phenolics Catechins/Epicatechins Flavan-3-ol Chocolate and tea From grape seeds Bitter White wine average 25 mg/l Red wine average 75 mg/l» Max ~ 800 mg/l Possible strong antioxidant

11 Phenolic Compounds - Types Produced by Grapes Flavonoid Phenolics Condensed Tannins From the Old German tanna (oak or fir) Polyphenol/Proanthocyanidins Increase in grape prior to véraison Most abundant type of phenol found in wine» 50 to 1500 mg/l Binds to and precipitates proteins» Tan leather the binding up of proteins in the skins of animals to make them less flexible and microbially unappealing Astringent» Binds to saliva proteins causing a decrease of slipperiness

12 Phenolic Compounds - Types Produced by Grapes Flavonoid Phenolics Condensed Tannins Polymer is not pure or stable Grape Skin Tannins - 3 to 83 units» Larger = astringent Grape Seed Tannins 2 to 16 units» Smaller = bitter Grape Seed tannins are more astringent than Skin tannins of equivalent size < 50% of tannins are extracted from the must Skin tannins extract early in fermentation Seed tannins extraction rate increases with time Maceration favors the increase of skin tannins

13 Phenolic Compounds - Types Produced by Grapes Flavonoid Phenolics Flavonols Found in the skin of the grape» quercetin-3-glucoside Increase as berry matures Produced in white and red grapes Sunscreen for grapes formation stimulated by UV light During fermentation glucose is lost glycosylated» Low solubility in wine Important in copigmentation Colorless but increase color intensity in young red wines

14 Copigmentation vs.

15 Phenolic Compounds - Types Produced by Grapes Non-Flavonoid Phenolics Hydroxycinnamates Found in the pulp of the grape Colorless, flavorless, odorless caftaric acid» ester of Cafeic and Tartaric Acids Coumaric acid

16 Phenolic Compounds - Types Produced by Grapes Non-Flavonoid Phenolics Hydroxycinnamates (continued) Potent oxygen scavenger (remember week 6???) Then the bisulfite ion (HSO 3- ) binds with the acetaldehyde

17 Phenolic Compounds - Types Produced by Grapes Non-Flavonoid Phenolics Hydroxycinnamates (continued) Potent oxygen scavenger (remember week 6???) Benzoquinones polymerize into brown compound» Responsible for browning of white wines Precursor for volatile phenol made by Brettanomyces

18 Phenolic Compounds - Types Produced by Grapes Non-Flavonoid Phenolics Stilbenoids Found in the skin of grapes Phytoalexins produced by plant due to stress» fungal attack Resveratrol» Thought to have anti tumor properties» Thought to prevent heart disease Concentration in wine 1 to 3 mg/l Therapeutic dose 8 mg/kg of body weight 266 bottles of red wine for 150 lb person

19 Phenolic Compounds - Source Produced by Wood Wood Hydrolyzable Tannins in Oak 8% by weight (European Oak) 1% by wieght (American Oak) In radial rays Anti-fungal Anti-insect» Ant/termite Modified by» Seasoning» Toasting Vanillin Breakdown product of Lignin» Water, UV light, fungi More in American Oak than in European Oak

20 Phenolic Compounds - Types Produced by Wood Wood Non-Flavonoid Phenolics Gallic acid» Not astringent Hydrolyzable Tannins/Ellagitannins» Polymers of gallic acid and glucose Bitter/astringent» < 20 mg/l in oak aged wine

21 Phenolic Compounds - Types Produced by Wood Wood Non-Flavonoid Phenolics Vanillin» Phenolic aldehyde» White wine - Smokey/Cinnamon» Red wine Coffee/Dark Chocolate/Smokey» Reaches maximum amount in ~ 1 year of oak ageing ~ 300 μg/l

22 Phenolics and Wine Ageing White wine Polymerization of Benzoquinones Browing

23 Phenolics and Wine Ageing Red wine At pressing the grape based phenolics are at their highest concentration Anthocyanins are quickly bonded to other compounds Almost completely gone by 3 year of ageing Yeast derived pyruvic acid to make vitisin A Acetaldehyde to make vitisin B Vitisins are highly colored (orange/red) and stable Concentrations in the mg/l range

24 Red wine Phenolics and Wine Ageing Anthocyanins are quickly bonded to other compounds Pigmented Polymers/Pigmented Tannins/Condensed Anthocyanins Polymers of Anthocyanins & Condensed Tannins» Condensed tannins are polymers of Catechins/Epicatechins Less astringent than condensed tannins

25 Red wine Phenolics and Wine Ageing Anthocyanins are quickly bonded to other compounds Pigmented Polymers/Pigmented Tannins/Condensed Anthocyanins

26 Phenolics and Wine Ageing Volatile Phenols Produced by Brettanomyces 4-ethyl phenol & 4-ethyl guaiacol Horse blanket, barnyard, bandaid, creosote From Hydroxycinnamates Coumaric acid

27 Next Week Clean up the Syllabus! A. Select the appropriate enzyme to create a specific wine style B. Assess the effect of different bacteria and molds on wine style and quality C. Use basic microbiological techniques D. Evaluate the effect of different yeasts on wine style E. Demonstrate knowledge of the nutritional needs of yeasts F. Plan and implement a successful alcoholic fermentation G. Demonstrate knowledge of the use of Botrytis cinerea in winemaking H. Demonstrate knowledge of yeast autolysis in Methode Champenois winemaking I. Implement plans to prevent undesirable effects caused by micro-organisms J. Estimate the effect of oxygen and lees on wine style and quality K. Implement plans to create high quality wine with different amounts of phenols L. Assess the factors that affect red wine color M. Demonstrate knowledge of flavor compounds