C5 Alcoholic Beverages

Question 1

What is the alcohol content of beer?

Answer 1

3-8%

Question 2

What are the types of beer available?

Answer 2

• Ales (Top fermented)
• Lager (Bottom fermented)
• Stout (Dark colored, top fermented beer)

Question 3

Differentiate between top and bottom fermentation.

Answer 3

Top fermentation: short-period fermentation where yeast rises at the top.

Bottom fermentation: A slow alcoholic fermentation where yeast cells collect at the bottom of the fermenting liquid. Takes place at low temperatures.

Question 4

Describe the raw materials needed for beer fermentation.

Answer 4

Yeast: For production of ethanol and carbon dioxide. Digest wort sugars and proteins

Malt: Barley malt, main source of nutrient for fermentation.

Hops: Addition to contribute to flavor, aroma, and body of beer.

Adjuncts: Additional ingredients (un-malted grains) added to supplement the main mash ingredients

Water: Stability and flavor of beer depends on water quality (i.e., pH and mineral contents)

Question 5

Describe the process of brewing.

Answer 5

1. Malting:
   Grains are partially germinated to form malt by soaking/steeping in water. Germination is halted by kilning.
2. Mashing and wort preparation:
   Milling is done prior to mashing. Milled ingredients are mixed with hot water and mashed until a liquid extract is separated from residual solid (Wort). The wort is then boiled.
3. Yeast fermentation:
   Yeast is added to ferment the wort via top/bottom fermentation.
4. Post-fermentation:
   Lagering for lager beer, cask and bottle conditioning of ales by adding priming sugar for secondary fermentation.
   Addition of papain and storage and ambient temperatures controls hazing.
   Addition of glucose oxidase prevents oxidation.

Question 6

What is kilning?

Answer 6

A process where germinated grains are heated in an oven at mild temperature.
Purpose:
- Stop embryo growth
- Stop enzyme activity
- Develops flavor and color

Question 7

What happens during the milling process?

Answer 7

• Protein hydrolysis
• B-glucan hydrolysis
• Starch hydrolysis

Question 8

Why is the wort boiled before fermentation?

Answer 8

• Inactivate enzymes
• Inactivate bacteria
• Provide bitterness and additional flavor/color compounds
• Concentration of wort
• Precipitate unwanted proteins
• Remove volatile compounds

Question 9

What are the conditions provided by beer that make the environment unsuitable for MO growth?

Answer 9

• Low pH
• Little to no oxygen
• Antimicrobial activity from hops constituents
• Low levels of carbon sources
• High concentration of ethanol

Question 10

What are the factors affecting the beer quality and the fermentation process?

Answer 10

• Amount of yeast for inoculation
• Yeast viability and quality
• Dissolved oxygen
• Concentration of soluble nitrogen and fermentable carbohydrate in wort
• Temperature

Question 11

What are the products of yeast fermentation?

Answer 11

• Ethanol
• CO2
• Glycerol
• Organic acids

Question 12

What are some microbiological problems observed in beer?

Answer 12

Microbial infections causes:
- Off flavos
- Sliminess
- Turbidity

Common contamination MOs increase LAB, AAB, yeasts coliforms.

Question 13

What are the special finishing process used to produce low alcohol beer?

Answer 13

• Vacuum Evaporation
• Reverse osmosis
• Dialysis
• Restricting ethanol production during fermentation

Question 14

What causes protein haze and how to remove haze?

Answer 14

• Proteins, polyphenols and metal ions
• Fixed by addition of papain, prolonged storage at ambient temperatures.