Ch.13: Wine, Beer, and Distilled Spirits

Chapter 13 of the book "On Food and Cooking: The Science and Lore of the Kitchen" by Harold McGee (1984) The Nature of Alcohol Beer Distilled Spirits Vinegar

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1. [Wine, Beer, and Distilled Spirits] Which microorganisms produce the alcohol in wine, beer and spirits?

   Yeasts, which convert the sugars of fruit or grain into alcohol. During fermentation yeasts also make dozens of new aroma compounds. McGee: "Yeasts are also prodigious flavor chemists."

2. [Wine, Beer, and Distilled Spirits] How does alcohol itself contribute to the flavor of wine or beer?

   It smells only faintly, so it forms a mild background for the grape or grain aromas.

3. [Wine, Beer, and Distilled Spirits] What is the basic difference between the raw material of wine and that of beer?

   Grapes are sweet and fragrant, ready to ferment; grains are dry, with no sugar or aroma. Grapes can be fermented only in the few days a year when they are ripe. Brewers make grains fermentable and aromatic by sprouting them or growing molds on them, then cooking them, at any time of year.

4. [Wine, Beer, and Distilled Spirits] What is a distilled spirit, compared with the wine or beer it is made from?

   A concentrate of the wine's or beer's alcohol and aromas.

5. [The Nature of Alcohol] Many living cells produce alcohol as a by-product of breaking down sugar for energy. What do most cells then do with this alcohol?

   They break the alcohol down further and use its energy too.

6. [The Nature of Alcohol] Which organisms release the alcohol they make into their surroundings, instead of breaking it down?

   Certain yeasts. This is why yeasts, and not other cells, are used to make wine and beer.

7. [The Nature of Alcohol] Why do yeasts excrete alcohol into their surroundings?

   To protect themselves against competing microbes: alcohol is toxic to living cells. The same defensive role as the lactic acid in cheese and pickles or the strong aromas of herbs and spices.

8. [The Nature of Alcohol] What are yeasts?

   Single-celled microscopic fungi. About 160 species are known. Brewer's yeast, electron micrograph. Each cell is about 0.005 mm across.

9. [The Nature of Alcohol] How does a yeast cell such as brewer's yeast, Saccharomyces cerevisiae, reproduce?

   By budding: a daughter cell grows out of the mother cell and then separates from it. One cell in this electron micrograph is budding; each earlier budding left a scar on the mother cell.

10. [The Nature of Alcohol] Are all yeasts useful to the cook?

    No: some spoil fruits and vegetables, and some cause human disease. Example: Candida albicans causes yeast infections.

11. [The Nature of Alcohol] Most yeasts used for bread, wine and beer belong to the genus Saccharomyces, "sugar fungus".

    Brewer's, baker's and the main wine yeast are all Saccharomyces cerevisiae.

12. [The Nature of Alcohol] Why do people deliberately grow yeasts in foods and drinks?

    Yeasts keep other microbes out, and what they make mostly tastes and smells good. Lactic acid bacteria are used to sour milk for the same two reasons.

13. [The Nature of Alcohol] Which ability of yeasts is essential to their production of alcohol?

    They can survive on very little oxygen. With plenty of oxygen, a cell burns its fuel completely to carbon dioxide and water. Without oxygen, the fuel is only partly broken down, and the leftover is alcohol.

14. [The Nature of Alcohol] What is the overall equation of alcoholic fermentation of glucose (energy production without oxygen)?

    C6H12O6→2 CH3CH2OH+2 CO2+energy\boldsymbol{\mathrm{C_6H_{12}O_6} \to 2\,\mathrm{CH_3CH_2OH} + 2\,\mathrm{CO_2}} + \text{energy}C6​H12​O6​→2CH3​CH2​OH+2CO2​+energy Glucose →\to→ 2 ethanol + 2 carbon dioxide + energy.Example: by molar masses, 180 g glucose gives 2⋅46=922 \cdot 46 = 922⋅46=92 g ethanol and 2⋅44=882 \cdot 44 = 882⋅44=88 g carbon dioxide, so about half the sugar's weight becomes alcohol.

15. [The Nature of Alcohol] Besides alcohol and carbon dioxide, which flavor compounds do yeasts add to grape juice or grain mash?

    Succinic acid A savory-tasting acid. Higher alcohols Longer-chain alcohols, made from the amino acids in the liquid. Esters Alcohols combined with acids; fruity-smelling. Example: ethyl esters smell of apple and pear. Sulfur compounds Aromas reminiscent of cooked vegetables, coffee and toast.

16. [The Nature of Alcohol] What happens to a yeast cell that dies in wine or beer?

    The cell's own enzymes digest it, and its contents are released into the liquid. Those contents go on producing flavor. This is the basis of aging wine on the yeast sediment, as in Champagne.

17. [The Nature of Alcohol] Why can a fruit juice or cereal mash have more nutritional value after yeast fermentation than before?

    Growing yeast cells synthesize proteins and B vitamins.

18. [The Nature of Alcohol] What were the first microorganisms ever isolated in pure culture?

    Beer and wine yeasts. They were isolated around 1880 at the Carlsberg Brewery's laboratory in Copenhagen. The question of how fermentation works drew Liebig and Pasteur and helped found microbiology.

19. [The Nature of Alcohol] Where does the word enzyme come from?

    From Greek for "in yeast", where sugar is transformed into alcohol. Enzymes are the proteins that living cells use to transform other molecules.

20. [The Nature of Alcohol] In chemistry, "alcohol" names a whole family of molecules. Which member is the alcohol of everyday speech?

    Ethyl alcohol, also called ethanol.

21. [The Nature of Alcohol] What are higher alcohols?

    Alcohols with a longer carbon chain than ethanol. Yeasts make them in small amounts, and distillation concentrates them in spirits.

22. [The Nature of Alcohol] Ethanol is CH3CH2OH\mathrm{CH_3CH_2OH}CH3​CH2​OH . Why does it mix both with water and with fatty substances?

    The CH3\mathrm{CH_3}CH3​ end resembles fats and oils; the OH\mathrm{OH}OH end is two-thirds of a water molecule. Ethanol next to a fatty acid and a water molecule.

23. [The Nature of Alcohol] Ethanol mixes with both water and fats. What can it therefore do to plant and animal cells?

    It passes easily through their membranes and pulls out aroma molecules and pigments. The pigments are carotenoids. So in cooking, alcohol is a third solvent besides water and oil.

24. [The Nature of Alcohol] What texture do higher alcohols give whiskies and other spirits?

    An oily, viscous texture. Their fat-like end is longer than ethanol's, so they behave more like fats.

25. [The Nature of Alcohol] Why are higher alcohols more irritating and stronger narcotics than ethanol?

    Being more fat-like, they accumulate in the membranes of our cells.

26. [The Nature of Alcohol] What is the boiling point of ethanol?

    78°C (176°F), well below that of water.

27. [The Nature of Alcohol] Which process depends on alcohol boiling at a lower temperature than water?

    Distillation, which turns wine or beer into a much stronger alcoholic liquid.

28. [The Nature of Alcohol] When brandy is flamed on a dish, why doesn't the food scorch?

    The heat of the flame goes into evaporating the spirit's water.

29. [The Nature of Alcohol] What is the freezing point of ethanol?

    −114°C (−173°F), far below that of water.

30. [The Nature of Alcohol] How can an alcoholic drink be made stronger in winter cold or in a freezer?

    By freezing part of its water into ice and removing it; the alcohol stays liquid. Ethanol freezes only at −114°C.

31. [The Nature of Alcohol] How heavy is a volume of ethanol compared with the same volume of water?

    80% as heavy, so water with alcohol in it weighs less per volume than plain water.

32. [The Nature of Alcohol] Which kind of cocktail relies partly on alcohol being lighter than water?

    Layered cocktails: liquids of different density stay in separate layers in the glass.

33. [The Nature of Alcohol] What does pure alcohol taste like?

    Slightly sweet, and at high strength pungent and "hot". The heat is an irritation felt by touch, not taste. Alcohol also has its own aroma, purest in vodka or unflavored grain alcohol. Its slight sweetness reflects a resemblance to sugar molecules.

34. [The Nature of Alcohol] How does alcohol concentration affect the release of other aroma molecules from a food or drink?

    Strong alcohol holds aromas back; about 1% or less helps them escape. So a little wine or vodka in a dish can intensify aroma, if the amount is small or most of it is cooked off. The aromas helped most are fruity esters.

35. [The Nature of Alcohol] What causes the tears or legs on the inside of a glass of strong wine or spirits?

    Alcohol evaporates from the film on the glass, and the watery rest pulls together into drops. Alcohol weakens the attraction between water molecules, so the more watery film clings more strongly to itself and the glass, creeps up and falls back as drops. More alcohol, warmth and wide shallow glasses give more pronounced tears.

36. [The Nature of Alcohol] How does alcohol kill living cells?

    It enters cell membranes and disrupts their proteins until the membrane fails. This happens at high enough concentration.

37. [The Nature of Alcohol] About what alcohol concentration can wine yeasts tolerate?

    About 20%. Most other microbes are killed by much less.

38. [The Nature of Alcohol] Why do distilled spirits, sherry and port not spoil after opening, while table wine and beer do?

    Their alcohol level is high enough to poison microbes. Acid or sugar in the liquid makes alcohol even more effective.

39. [The Nature of Alcohol] Alcohol is a depressant narcotic. Why does it make people more animated at first?

    It first depresses the higher brain functions that normally inhibit our behavior. More alcohol then impairs memory, concentration, thinking, coordination, speech and vision.

40. [The Nature of Alcohol] Why can a large person drink more than a small one with the same degree of intoxication?

    A larger body has more fluid to dilute the alcohol, so the concentration in its cells is lower. Absorbed alcohol is distributed by the blood to all body fluids and diffuses into all cells.

41. [The Nature of Alcohol] What blood-alcohol concentrations give impaired coordination, falling-over drunkenness, and danger of death?

    0.02 to 0.03%: impaired coordination; 0.15%: falling-over drunk; 0.4%: can be fatal.

42. [The Nature of Alcohol] Why is alcohol considered a relatively weak drug?

    Noticeable effects take grams of pure alcohol, not milligrams. Habitual heavy drinking is still addictive and destructive; alcohol and its first metabolite, acetaldehyde, damage many organs.

43. [The Nature of Alcohol] How many calories does a gram of alcohol provide, compared with sugar and fat?

    About 7 kcal/g, between sugar (4) and fat (9). In the American diet, about 5% of all calories come from alcohol.

44. [The Nature of Alcohol] What is the first-pass metabolism of alcohol?

    The breakdown of part of the alcohol in the stomach, before it reaches the small intestine and the blood. The rest is broken down in the liver.

45. [The Nature of Alcohol] What share of the alcohol they drink do men and women break down in the stomach?

    About 30% in men, only about 10% in women. So blood alcohol rises more slowly in men, and they can drink more before feeling the effects.

46. [The Nature of Alcohol] How much alcohol can the body break down per hour?

    About 10 to 15 g, i.e. one standard drink every 60 to 90 minutes.

47. [The Nature of Alcohol] How long after drinking does the alcohol level in the blood reach its peak?

    30 to 60 minutes.

48. [The Nature of Alcohol] How does eating, especially fatty food, change the rise in blood alcohol after a drink?

    The rise is slower, and the peak is about half as high as on an empty stomach. Food keeps the alcohol longer in the stomach, so the stomach's enzymes break down more of it.

49. [The Nature of Alcohol] How does aspirin change the rise in blood alcohol after a drink?

    Blood alcohol rises faster. Aspirin interferes with the breakdown of alcohol in the stomach.

50. [The Nature of Alcohol] Do the bubbles of sparkling wine and beer change how fast blood alcohol rises?

    Yes, carbon dioxide bubbles make it rise faster. How they do so was unknown in 2004.

51. [The Nature of Alcohol] Do people who drink one or two drinks a day die less often of heart disease?

    Studies up to 2004 said yes: fewer deaths from heart disease and stroke. Higher consumption goes with more deaths from cancer and accidents. Later, larger studies have questioned whether moderate drinking has any net benefit.

52. [The Nature of Alcohol] How does alcohol itself lower the risk of heart disease?

    It raises "good" HDL cholesterol and reduces the blood's tendency to clot.

53. [The Nature of Alcohol] Which health benefit do red wine and dark beer offer beyond the alcohol?

    They supply antioxidant phenolic compounds. Wine phenolics also widen arteries and make red blood cells less sticky; resveratrol inhibits cyclooxygenase, an enzyme linked to inflammation, arthritis and some cancers.

54. [The Nature of Alcohol] Why do we feel ill the morning after drinking too much (a hangover)?

    Partly withdrawal: the body got used to the alcohol overnight, and now it is gone. Example: sensitivity to light and sound may be the nervous system still compensating for the alcohol's depressant effect.

55. [The Nature of Alcohol] Why does a morning drink ("hair of the dog") seem to cure a hangover?

    It restores the alcohol the body had adjusted to and slightly numbs it, but only postpones recovery.

56. [The Nature of Alcohol] Why can drinking water help against a hangover?

    Alcohol dehydrates the body, and the dehydration causes dry mouth and headache.

57. [The Nature of Alcohol] Why can coffee or tea ease a hangover headache?

    Alcohol widens the blood vessels of the head, and caffeine narrows them.

58. [The Nature of Alcohol] What flavors do wine, beer and spirits add to cooked dishes?

    Acidity, sweetness, savoriness and aroma. The savoriness comes from glutamic and succinic acids. Alcohol also acts as a solvent and a reactive ingredient. Problems for the cook: astringency of red wine, bitterness of beer, and alcohol's own harshness in hot food.

59. [The Nature of Alcohol] How much of the added alcohol remains after a long-simmered stew, a briefly cooked dish, and a flambé?

    Stew: about 5%. Brief cooking: 10 to 50%. Flambé: up to 75%. No cooking method removes alcohol completely.

60. [The Nature of Alcohol] Which flavor compounds does oak heartwood contain?

    Tannins The main defensive compounds, against boring insects. Eugenol Clove-like aroma. Vanillin Vanilla aroma. Oak lactones The characteristic "oaky" aroma; relatives of coconut and peach aromas. 90 to 95% of heartwood solids are insoluble cell-wall molecules (cellulose, hemicellulose, lignin); strong alcohol partly extracts lignin, and heating during barrel making turns all of them into new aromas.

61. [The Nature of Alcohol] Which oak is used mostly for wine barrels, and which for spirit barrels?

    European oak for wine; American oak, mainly white oak (Quercus alba), for spirits.

62. [The Nature of Alcohol] How does American oak differ from European oak in the flavor it gives?

    American oak gives less tannin and more oak lactones and vanillin.

63. [The Nature of Alcohol] How do the insides of European barrels and American whiskey barrels get heat-treated?

    European barrels are toasted for minutes; whiskey barrels are charred by a flame for seconds. Toasting: 150 to 200°C (300 to 400°F) for 5 to 20 minutes, shorter for wine barrels, longer for spirit barrels. Charring: an open gas flame for 15 to 45 seconds.

64. [The Nature of Alcohol] What four things happen to an alcoholic liquid stored in a new barrel?

    Extraction The liquid dissolves tannins, oak, clove and vanilla aromas, sugars, browning products and smoky compounds from the heated wood. Absorption In charred whiskey barrels, the carbon surface absorbs some substances, like activated charcoal, and speeds maturation. Oxygen uptake Pores and gaps in the wood let in a limited amount of oxygen. Slow reactions Liquid, wood components and oxygen react toward a stable, balanced flavor.

65. [The Nature of Alcohol] How can a winemaker limit the oak flavor of new barrels?

    Use new barrels for a shorter time, or use old barrels. Used barrels have already lost much of their extractable flavor.

66. [The Nature of Alcohol] Barrel-fermented wines have a roasted-coffee, roasted-meat note. Where does it come from?

    Yeast enzymes act on compounds in the toasted oak and produce furfurylthiol, a sulfur compound.

67. [The Nature of Alcohol] How do cheaper wines and brandies get oak flavor without barrels?

    Oak chips, staves or sawdust are put in steel tanks. French brandies may use boisés: extracts of wood chips boiled in water.

68. [Wine] Why are grapes especially suited to making wine?

    Tartaric acid Few microbes can metabolize it, and it favors yeasts. Enough sugar The alcohol that yeasts make from it suppresses nearly all other microbes. A productive, adaptable vine It grows in a wide range of soils and climates. Color and flavor Striking colors and a variety of flavors. About 70% of the world's grape crop, its largest fruit crop, is made into wine.

69. [Wine] How old is winemaking?

    At least 8,000 years: wine residues from about 6000 BCE were found in a pot in western Iran. The earliest evidence known in 2004. The first wines were red; the Egyptians made white wine from a color mutant.

70. [Wine] When wooden casks replaced sealed clay jars, why did well-aged wines disappear for over a thousand years?

    Casks let air in, so wine overoxidized within a few years. The ancient Egyptians and Romans had aged wine for years in airtight clay jars (amphoras). Long aging returned only in the 17th and 18th centuries with glass bottles and cork stoppers.

71. [Wine] Why did wine bottles have to become slim before wine could be aged in them for years?

    A slim bottle can lie on its side, so the wine keeps the cork wet and tight. A dry cork shrinks and lets air in. The earlier short, stout bottles only carried wine from barrel to table.

72. [Wine] What allowed the English to make sparkling Champagne in the 17th century?

    Gas-tight cork stoppers and glass bottles strong enough to hold the pressure. The glass was strong because it was made with coal fires instead of wood fires.

73. [Wine] What role does oxygen play in making and aging wine?

    Some oxygen in the barrel matures young wine; keeping it out in the bottle preserves mature wine. Pasteur, 1866: "it is oxygen which makes wine; it is by its influence that wine ages".

74. [Wine] How do industrial wines imitate traditional ones?

    They adjust the wine's makeup by separation technology and fake aging with oak chips and bubbled oxygen. Water, sugar, acid and alcohol are adjusted; the oak chips and oxygen go into steel tanks.McGee: "Industrial wines are marvels of reverse engineering."

75. [Wine] What are the five groups of grape components that matter for wine?

    Sugars 20 to 30% at harvest, mainly glucose and fructose; the yeasts' food. Acids Mainly tartaric, some malic: they hinder unwanted microbes during fermentation and are major flavor components. Tannins and other phenolics Astringency, and with it body. Pigments Red grapes: anthocyanins, mainly in the skins. "White" grapes: yellowish flavonols. Aroma compounds Many bound to sugars and odorless in the fruit, freed by fruit and yeast enzymes during winemaking.

76. [Wine] About how many varieties of the Eurasian wine grape Vitis vinifera exist?

    About 15,000.

77. [Wine] What is a clone of a grape variety?

    Genetically identical vines grown from cuttings of a single plant. A variety consists of many slightly different clones.Example: Pinot Noir exists in several hundred clones.

78. [Wine] Which grape varieties are called noble?

    Those whose wines can develop great complexity over many years in the bottle. Example: Cabernet Sauvignon, Pinot Noir, Chardonnay, Nebbiolo, Sangiovese, Riesling.

79. [Wine] How does an abundance of each of these affect wine grapes: water, soil nitrogen, sun and warmth?

    Much water Watery fruit. Much soil nitrogen Too many leaves, which shade the fruit and give it odd flavors. Much sun and warmth Plenty of sugar but less acid and aroma, so a strong but flat wine.

80. [Wine] Which growing conditions give the best wine grapes?

    Barely enough water, minerals, light and heat, so the grapes ripen fully but slowly.

81. [Wine] Why does the vintage (year of harvest) of a wine matter?

    The weather differs from year to year, so the same vineyard makes better wine in some years.

82. [Wine] The influence on a wine of the particular place where its grapes grew (soil, water, slope, orientation, microclimate) is called terroir.

    Example: a south-facing slope can get 50% more autumn sunlight than level ground, lengthening the season of flavor accumulation.

83. [Wine] What are the three stages of making a basic table wine?

    Crushing the grapes, fermenting the juice, and aging (maturing) the new wine.

84. [Wine] Which part of the grape holds most of its color, tannin, acid and aroma?

    The skin. Stems hold bitter resins; seeds hold tannins, oils and resins. So stems are removed and seeds kept unbroken during pressing. Cross-section of a grape: stem, skin, pulp and seeds.

85. [Wine] What is the free run juice of crushed grapes?

    The first juice that flows out, mostly from the middle of the pulp: clear, sweet and nearly tannin-free.

86. [Wine] How does pressing the grapes harder change the juice?

    It adds juice from under the skin and around the seeds, which has a more complex character. How hard the grapes are pressed strongly affects the final wine.

87. [Wine] The liquid from crushed grapes, about 70 to 85% water, 12 to 27% sugars and 1% acids, is called the must.

88. [Wine] How does the handling of the grape skins differ between white wine and red or rosé wine?

    White: skins removed before fermentation. Red and rosé: fermented with the skins. For white wine the skins come off after a few hours; red and rosé are fermented with them for part of the time. Longer contact and harder pressing give deeper color and more astringency.

89. [Wine] Why is sulfur dioxide added to the must before fermentation?

    It suppresses wild yeasts and bacteria, and prevents oxidation of flavor and pigment molecules. It increases sulfites in the wine, which some sensitive people react to. The practice is centuries old.

90. [Wine] Why do winemakers in cool climates, such as France, often add sugar to the must?

    Cool-climate grapes may not have enough sugar to give enough alcohol for a stable wine.

91. [Wine] Why do winemakers in hot climates, such as California, often add acid to the must?

    Grapes ripening in heat use up some of their acid, which would give a flat-tasting wine. The acid added is tartaric acid.

92. [Wine] Which yeasts start a wine fermentation when no starter culture is added?

    Wild yeasts that live on the grape skins. Genera Kloeckera, Candida, Pichia, Hansenula and others. These wild yeasts add flavor compounds to the finished wine.

93. [Wine] In a spontaneous wine fermentation, which yeast always replaces the wild yeasts in the end?

    The yeast Saccharomyces cerevisiae, because it tolerates more alcohol.

94. [Wine] During wine fermentation, what do yeasts contribute besides alcohol?

    New aromas, and release of the grape's own aromas from odorless bound forms. The new aromas are higher alcohols and esters, which the grape cannot supply. The grape aromas are bound to sugars and are freed by yeast and grape enzymes and the acid conditions.

95. [Wine] At what temperature, and for how long, are delicate white wines fermented?

    At about 16°C (60°F) for 4 to 6 weeks.

96. [Wine] At what temperature, and for how long, are red wines fermented?

    At 18 to 27°C (65 to 80°F): 4 to 14 days with the skins, then without them, 2 to 3 weeks in total. The warmth and skin contact extract pigments, tannins and flavor from the skins.

97. [Wine] How does fermentation temperature affect wine aroma?

    Lower temperature: slower, longer fermentation and more aroma molecules accumulate.

98. [Wine] What is a dry wine?

    A wine with no residual sugar: the yeasts have turned essentially all of it into alcohol. Sweet table wines are made by stopping fermentation early or, more often, by adding unfermented juice after the yeast is removed.

99. [Wine] What is the malolactic fermentation of wine?

    A bacterial fermentation after the yeast fermentation that turns malic acid into the milder lactic acid. The wine tastes less tart and gains aromas such as buttery diacetyl. The bacterium is Leuconostoc oenos. Some winemakers prevent it to keep the wine's sharpness.

100. [Wine] Letting yeast and grape particles settle and moving the cleared wine into a fresh container, leaving the sediment behind, repeated every few months, is called racking.