Alcoholic beverage (II)

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Alcoholic beverage (II)
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Wine Making

• Sulfur Dioxide Treatment
• Use wine starter cultures versus spontaneous
  (natural) fermentation
• Inactivate indigenous microflora
• Minimize competition and interference
• Heat-treatment detrimental to juice and wine
• Sulfite-treated, most commonly SO2 gas or
  potassium bisulfite
• Inhibit wild yeast as well as acetic
  acid-producing microbes, malolactic bacteria, and
  various fungi
• Control deleterious chemical reactions
• Oxidation and browning

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Microbial Ecology

• Yeast primarily associated with grape surface
  Kloeckera apiculata
• S. cerevisiae introduced into the must durng
  handling and crushing, most likely from the
  equipment
• Succession
• Must as selective environment
• Low pH
• Presence of organic acids
• High sugar conc and high osmotic pressure
• CO2 anaerobic, restrict growth of aerobic
  organisms
• Ethanol
• Sulfite

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Microbial Ecology

• Saccharomyces less than 10 of the initial yeast
  population
• K. apiculata dominant
• Produce 6 ethanol from glucose and fructose
• Low ethanol tolerance, inhibited by 3-4 ethanol

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Separation and Pressing

• Juice separated from seeds, skins, and pulp
  (pomace) using screens by gravitational forces
• 75 free run juice, more juice recovered by
  various processes (pressed juice)
• Clarification
• Settling, decantation, filtration or
  centrifugation

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Fermentation

• Limited fermentation before addition of starter
  culture
• Culture added to the must
• after pressing and clarification for white wine
  making
• Before seed and skin removal for red wine (during
  maceration)
• Traditional fermentation in open barrels, closed
  stainless steel tanks now more common

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Fermentation

• Temperature
• 7-20C for white wine
• 20-30C for red wine
• Low temp loss less ethanol and volatile flavors
  due to evaporation
• Produce more flavor compounds, ethanol and less
  sugar left
• Wine fermentation generates heat, too much may
  affect wine fermentation (stuck)
• Typically fermentation takes 3-5 days at 10-15C
• Adjustments, blending, clarification
• Aging

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Malolactic Fermentation

• As important as the yeast fermentation to wine
  quality
• Acidity 3.3-3.6 for red wine, white wine slightly
  more acidic
• High level organic acids, excess acidity serious
  flavor defect
• Malic acid important to influence acidity
• Decomposition into lactic acid via malolactic
  fermentation (fig 10-4)
• Several LAB, particularly Oenococcus oeni
  (previously Leuconostoc), some Lactobacillus

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Types of Wine

• Sweet wines
• noble rot by Botrytis cinerea
• Dehydration of grapes
• 9-13 ethanol, as much as 10 unfermented sugar
• Fortified wines
• Added distilled spirits (containing as much as
  95 ethanol) to raise ethanol conc to 15

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Sparkling wines

• Foam readily due to the presence of high
  concentration of dissolved CO2
• 4.05-5.06 Pa (4-5 atm) at 20C (general), 2.03 Pa
  (2 atm) (US)
• Methods of production
• Champagne process (bottle fermentation, remove by
  disgorging)
• Transfer profess (bottle fermentation, transfer
  to a tank, and removal of the yeast by
  filtration)
• Bulk fermentation
• Carbonation

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Champagne Process
Dry white wine
Sucrose 25g/l, pure culture yeast
Secondary fermentation
9-12C, closed bottle Several months
Rest for months-years
Yeast is collected and frozen in the neck of the
bottles
Disgorge
Lost volume replaced by a sucrose solution
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Other processes

• Transfer process
• Bottle fermentation
• Yeast removed by transferring wine to a tank with
  nitrogen pressure
• Add dosage, filtered and bottle filled with
  nitrogen or CO2 counterpressure
• Bulk fermentation
• Mass production, fermentation carried in
  pressured vessel
• Filtration and bottling
• Carbonation
• No secondary fermentation

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Vinegar
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Vinegar

• Can be make from almost any fruits, grains, mash
  (alcohol-containing), beer and wine
• Contains at least 4 g of acetic acid per 100 ml
  (20C)
• pH 2-3.5

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Chemistry
Acetic acid
Sugar
Alcohol
Acetic acid
Lactic acid
Acidic acid bacteria Acetobacter Gluconobacter, G
luconoacetobacter, Acidomonas
Lactic acid bacteria, yeasts
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Vinegar Fermentation

• Oxidative fermentation, ethanol oxidized with air
  to acetic acid and water
• By Acetobacter spp.

C2H5OH O2
CH3COOH H2O
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Varieties

• Wine vinegar
• From grape wine
• Cider vinegar
• From apple cider
• Malt vinegar
• Barley malt or cereals, with starch converted by
  the malt
• Rice vinegar
• Saccharification of rice starch, followed by
  alcoholic and acetous fermentation
• Sugar vinegar, whey vinegar, fruit vinegar, etc.

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Nutrients and water requirements

• Usually dont need additional nutrients
• Ammonium phosphate sometimes is added to apple
  cider and some grape wines
• Water free from chlorine
• Additional nutrients required to make distilled
  vinegar

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Behavior of Acetobacter in vinegar fermentation

• Lack of oxygen
• Significant cell damage 10-100, depend on the
  duration
• Lack of ethanol
• Cause sever damage to the cells
• Changes in temperature
• Temperature circulation too quick, cause cell
  damage
• Over-oxidation
• Undesirable oxidation to CO2
• automation
• Growth rate, etc.

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Conditions for vinegar fermentation

• Step 1 alcoholic fermentation
• Organism(s) involved
• Fermentation condition
• Step 2 acetification
• Organism(s) involved
• Fermentation condition