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Food Fermentation > Brewing > Flashcards

Brewing Flashcards

1
Q

What are the four main ingredients necessary for brewing?

A
  1. Malted barley
  2. Water
  3. Hops
  4. Yeast
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2
Q

What are the two types of barley and what is their difference?

A

6-row barley (America beer) -> high protein
2-row barley (German beer)-> low protein, more fermentable sugars

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3
Q

What are the steps in brewing?

A
  1. Malting
  2. Milling
  3. Mashing
  4. Lautering
  5. Boiling
  6. Cooling
  7. Fermenting
  8. Maturation
  9. Filtering
  10. Packaging
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4
Q

What is the purpose of malting?

A

To release starch by degrading endosperm cell wall and activate enzymes (proteases and starch degrading)

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5
Q

What are the three steps of malting? And what is their role?

A
  1. Steeping -> soaking grain for germination
  2. Germination -> formation of root and enzymes
  3. Kilning -> stop germination by drying malt
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6
Q

What is the name of the pathway activated during germination? and when does it get activated?

A

Gibberellic acid (GA) pathway and is activate at moisture 27%. It uptakes O2 and releases CO2 and heat.

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7
Q

What does the GA pathway do?

A

Promotes enzyme production for cell wall, starch and protein degredation.

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8
Q

Which enzyme is responsible for the degredation of the cell wall?

A

B-glucanase more specifically lichenase and endo-beta-glucanase.

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9
Q

What is the difference between licheanase and endo-beta-glucanase?

A

That lichenase can cleave B 1-4 and 1-3 linkage while endo-beta-glucanase only 1-4 linkages

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10
Q

Can B-glucanase degrade starch?

A

No, starch is alpha -1-4 linakges

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11
Q

How can one visualize B-glucan degradation?

A

By calcofluor staining + UV light

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12
Q

What are the two type of starch and which enzyme are resposible for starch break down?

A

Amylose and amylopectin.
alpha-amylose cleaves backbone while B-amylose cleave dimer of maltose from non reducing ends.
other debranching enzyme are responsible for the branches.

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13
Q

Is the optimum temperature of starch or protein enzyme higher?

A

Starch enzymes have higher optimum temp.

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14
Q

What are the two steps in kilning and what is their role?

A

First step is at 50C to reduce H2O to 10-12% this allows enzymes to be more stable but still active.
Second step is at 80 C to reduce H20 to 5%. Enzyme are inactivate and maillard and caramellization reaction occur which give flavor.

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15
Q

If temp higher than 80 C are used in the second step of kilning what are the consequences?

A

Produce darker malt.

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16
Q

Milling is the second step of brewing. What is its purpose?

A

To increase surface area which will provide optimal conditions during mashing.

17
Q

What is the purpose of mashing?

A

To form an extract with desirable sugar and protein profile.

18
Q

What is a product added to mashing?

A

Water, its quality is important.

19
Q

What are the two methods of mashing? and what are their main difference?

A
  1. Infusion
    In infusion water is mixed with malt (1) and temperature is increased to four stages. (2) temp is 52C where protein enzyme are optimal for protein degradation. (3) temps is 68C for starch degrading enzymes and (4) enzyme inactivation.
  2. Decoction
    Adjuncts are added to malt which are boiled on a separate vessel. This lead to increase of temperature and further decrease. This allows to go through all 4 stages.
20
Q

What are adjuncts and what happens if u add more of it?

A

Adjuncts are starch material which include rice and maize. The more u add the more starch is added leading to more malty flavor and alcohol.

21
Q

After mashing lautering is required. What is its purpose?

A
  1. Removal of suspended matter (spent grain) from dissolve matter (wort)
  2. Removal of microorganisms
22
Q

The wort is obtained after lautering to which hops are added. The solution is then boiled. Why?

A

To sterilize the wort, increase color, reduce pH and isomerize the hop to obtain bitterness.

23
Q

With boiling alpha acid which are not soluble and not bitter are transformed into iso alpha acid which are soluble and bitter. What are advantage and disadvantages of this compounds?

A

Advantages:
- Antimicrobial -> prevents LAB growth
- bitterness
- stabilize foams
Disadvantages
- sensitive to light and can then produce stinky aroma -> prevented with brown glass

24
Q

What is the purpose of cooling?

A

To reduce temperature to fermentation temperatures

25
Q

What is the purpose of fermentation?

A

To convert fermentable sugars to ethanol

26
Q

How is lambic beer produce?

A

Is a belgian beer which relies on spontaneous fermentation of an open vessel maintained in a cool environment.

27
Q

How can one analyze alcohol in the beer?

A
  1. HPLC
  2. Hydrometer (ratio of density sample/density water
28
Q

What aromas are produced through fermentation?

A
  1. Higher alcohols
  2. Higher esters
  3. Organic sulfur compound
  4. Acetolate -> become diacetly after yeast conversion and gives buttery flavor
29
Q

What are the main higher alcohols?

A
  1. 1-propanol
  2. 2-propanol
  3. butanol
  4. amyl alcohol
30
Q

Why do we leave beer to mature?

A

Because off flavors are reduced and nice flavors are improved.

31
Q

What are the substance which improve foam in beer?

A
  1. Protein
  2. Bitter substances
32
Q

What protein is responsible for improving foam in beer?

A

LTP1 which after boiling unfolds and becomes better foaming agent

33
Q

Are lipids beneficial to foam?

A

No, they are detrimental

34
Q

What is the purpose of filtering?

A

To make a bright beer and stable.

35
Q

What are disadvantages of alcohol free beer?

A

Loss of flavor and shorter shelf life

36
Q

What are the two methods to obtain alcohol free beer?

A
  1. Vaccum evaporation
  2. limit ethanol conc. by using high yeast cell conc.

Food Fermentation (12 decks)

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