Alcoholic fermentation converts sugars into ethanol and carbon dioxide through the metabolic process of yeasts. The major reaction is glucose transforming into carbon dioxide and ethanol. Beer production involves malting grains such as barley to activate enzymes, mashing to extract soluble substances, boiling with hops, fermentation using bottom- or top-fermenting yeasts, conditioning, and packaging. Factors like temperature, oxygen supply and sugar content affect fermentation.

1. Alcoholic fermentation

2. Alcoholic fermentation:
Simple sugars yeasts
ethanol

3. Special flavors and aromas of beers arise
from minor biochemical reactions
Major Reaction: Glucose to Carbon
Dioxide and Ethanol

4. Ingredients
• Water
–Or “H₂O”
• Starch
–The most important ingredient
for providing character to a
beer
–Most common source is malted
grain

5. Ingredients
• Hops
–From the flower of the hop
vine
–Provide bitterness to balance
the sweetness of the malt
–Add floral, citrus, and herbal
aromas and flavours
• Clarifying Agent
–Used to precipitate any leftover
proteins after brewing
• Spices and fruits
• Preservative

6. Ingredients
• Yeast
–Responsible for fermentation
(metabolizing sugars from the
malt)
–Can influence the flavour of the
beer
–Antibiotic properties favour
brewers yeast over less
desirable microorganisms

7. Yeast
Saccharomyces spp.Saccharomyces spp.

8. Qualities of Yeasts
• Rapid and relevant carbohydrate
fermentation ability;
• Appropriate flocculation and sedimentation
characteristics
• Genetic stability
• Osmotolerance

9. Qualities of Yeasts
• Ethanol tolerance
• Ability to produce elevated concentration of
ethanol;
• High cell viability for recycling;
• Temperature tolerance.

10. Alcoholic fermentation is affected by:
• Oxygen supply
• Sugar content
• Alcohol content
• Temperature

11. Alcoholic fermentation processes

12. Other types of fermentations
CoASH
pyruvate acetyl-CoA + acetyl-P acetate
acetaldehyde
ethanol
NADH, H+
NAD+
ADP ATP
NADH, H+
NAD+
lactate

13. Production of beer

14. Kinds of beer
• Bottom fermented
• produced using Saccharomyces uvarum;
• also called Lager beer
• Examples: pilsner, Dortmund, Munich,
Weiss

15. Kinds of beer
• Top fermented
• produced using Saccharomyces cerevisiae
• Generally referred to as Ale, but other
products are poter, stout

16. Process of beer production
• The process goes through certain steps:
– Malting
–Mashing
–Boiling
–Fermentation
–Storage/treatment
–packaging

17. Malting

18. Malting
• Grain is soaked to expedite germination, then
dried and roasted in a kiln
• Malting is sprouting grains in a controlled
environment until a certain level of
modification is obtained and then the kernels
are dried and kilned until a specific color is
achieved.

19. Malting Process
• Collection of cereal
–Clean and steep in water
• Steeping
–Steep the barley in water at 10-15°C for two
to three days until water content is 45%
–Change water every 12hrs to remove
microorganisms that may grow within the
interval
–Drain the water and spread under cover to
germinate or sprout for six to ten days
–Gibberellic acid can be added to aid
sprouting reducing malting time

20. Malting Process
• Enzymes are active at this time.
• Under good conditions, signals (AG3 and
cytokinin) into the endosperm to stimulate
enzyme secretion from the coat.
• The enzymes are α - amylase and β -
amylase.
• The stimulate the break down of starch to
maltose hence malting

21. Malting Process
• Enzymes are active at this time.
• Proteases are also produced from the
alleurone to break down proteins.
• The embryo uses the metabolites for
sprouting

22. Malting Process
• Drying and Kilning
• After germination, the temperature is slowly
raised to 90 °F and held at this temperature
for 24 hours to allow enzymes to work
• The temperature is raised to 120 °F and held
for 12 hours to dry the malt
• The malt is kilned at the prescribed
temperature to achieve the correct color

23. Malting Process
• Cleaning of malt
– Using magnets, blowers, sieves
• Milling of malt
– To remove the husk and break starch into
fine grains for increased surface area
• Marshing of malt
– To extract the soluble and solubilise some
insoluble substances
– Adjunks should then be added

24. Malting Process
• Separation and filtration
– The mixture of marsh and adjunks is wort
– To remove the husk and insoluble
substances from soluble

25. Boiling wort with hops; to:
– Concentrate filtrate
– sterilised filtrate
– inactivate enzymes,
– develop colour,
– remove some volatile materials
– extract soluble substances from hops
– coagulate and precipitate proteins
– contribute antiseptic resins: humulone,
cohumulone, adhumulone.
• The boiled substance is trud

26. Malting Process
• Cooling
– The mixture is cooled so proteins are
precipitated
– The cooled mixture is sludge is filtered
– The filtrate is cold wort

27. Fermentation

28. Fermentation
• The wort is transferred to fermenter and
inoculated with yeast
• What may happen next depends on type of
fermentation

29. Adding yeast to the fermenter

30. Fermentation Tanks
After the yeast is added to the wort, fermentation
of the maltose to Ethanol occurs in these tanks.

31. Fermentation
• What may happen next depends on type of
fermentation
–Top
–Bottom

32. Top-fermentation
• Top fermenting yeast rises to the top of the
vessel during fermentation.
• Fermented at higher temperatures than lager
beer (15–23°C )
• Treatment
–Addition of sugar, caramel and little yeast
to use up the sugar added
–Carbonation and kept for 7 days
–Product is fined by precipitating insoluble
substances
• packaging

33. Bottom -fermentation
• The most commonly consumed
• Fermentation occurs at around 7-12°C using a
“bottom fermenting” yeast
• Then cooled at 0-4°C
• “Lagering phase”
• German meaning storage in silos for 6months
during which the following occur
–Carbonation because CO₂ is produced
–Removal of undesirable volatile substances
–Formation of desirable esters giving good
flavor

34. Bottom -fermentation
• Period can be shortened by
–Artificial carbonation
–Addition of active wort
–Warm lagering at 14 ⁰C
• Product is filtered and packaged

35. Packaging
• Oxygen entry is prevented
• CO₂ is prevented from escaping
• Pasteurization before or after packaging

36. Hazing: Major defect
• Causes
–Biological reasons
• Microorganisms (yeast and bacteria)
–Physico – chemical reasons
• Presence of Fe and Cu, proteins, polyphenols,
carbohydrates
–Use of old cereal
• Gives wild beer producing foam when opened
–Exposure to sun radiation
• Leads to formation of mercaptans (off flavour)

38. Alcoholic fermentation (yeast lacks Lactate DH)
2. alchohol
dehydrogenase
C-O-
C=O
CH3
O
Pyruvate
H-C-O-
H
H
NADH, H+
NAD+
1. Pyruvate
decarboxylase (TPP)
Mg2+
, thiamine
pyrophosphate
CO2
CH3
H-C=O
Acetaldehyde
Ethanol
CH3