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Microbiology > Semester 2- Alcohol -role of microorganisms > Flashcards

Semester 2- Alcohol -role of microorganisms Flashcards

1
Q

Brewing

A

manufacture of alcoholic beverages from malted grains

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2
Q

two main types of brewery yeast strains

A
  • top fermenting (ales)

- bottom fermenting (lagers)

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3
Q

beer yeasts

A

-ability to produce fermentation, flocculate, desired products (aroma and flavour)

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4
Q

starter culture

A

-from previous batches or pure strains

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5
Q

Malting

A

Barley –> Malt

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6
Q

Malt

A

contains various enzymes amylases (starch–>maltose) and proteases essential for the brewing process

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7
Q

Dried malt

A

enzymes stable

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8
Q

Mashing

A

Malt–>grist–>wort

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9
Q

Fermentation :ALE

A
  • batch fermentation in large open vats
  • top fermenting yeast
  • strains of Saccharomyces cerevisiae
  • 5-6 days
  • aerated
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10
Q

Fermentation: LAGER

A
  • produced by closed batch fermentation
  • use of bottom feeding yeasts
  • strains of Saccharomyces carlsbergensis
  • 8-14 days
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11
Q

Maturation

A
  • storage, finishing, distribution

- lager stored at -1, ale at 4-8

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12
Q

Chemistry

A

Maltose–>glucose–>pyruvate–>acteladehyde + CO2–>ethanol

Maturation = esters

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13
Q

Spoilage

A

certain bacteria and yeasts cause spoilage of beer due to :

  • low pH
  • alcohol content
  • hop extracts
  • low storage temps
  • anaerobic conditions
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14
Q

Examples of spoilage organisms:

A
  • lactobacillus (acidity)
  • Acetobacter )souring)
  • Wild yeast (EG S.pasteurianus)
  • Pediococcus cervisiae (diacetyl)
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15
Q

Spoilage prevented by:

A
  • aseptic and hygiene precautions
  • regular cleaning and sterilisation of equipment
  • use of pure strains
  • pasteurisation
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16
Q

Wine Production:

A
  • grapes harvested (early autumn)
  • crushed to give must (juice)
  • contact with skins (Red wine)
  • Sterilisation with SO2
  • Addition of yeast (Saccharomyces ellipsoideus)
  • Fermentation of must
  • Ageing, racking, clarification, filtration
  • bottling
17
Q

Wine Production II

A
  • some wines undergo a secondary (malolactic) fermentation
  • convert malic (bitter) to lactic acid (smoother)
  • catalysed by acid-tolerant lactic acid bacteria (Lactobacillus, Pediococcus, Oenococcus)
  • add starter cultures then store wine in barrels
  • bacteria that stick to insides of barrels (used for any further rounds of malolactic fermentation)
18
Q

Distilled Spirits: Whisky

A
  • omission of boiling of wort
  • omission of hops
  • drying of malt in peat-fired kilns for distinct flavour
19
Q

Brandy (cognac)

A

distillate of wine

20
Q

Rum

A

-distillate of fermented molasses

21
Q

Vodka

A

-distillate of fermented potatoes or grain

Microbiology (19 decks)

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