Industrial Microbiology and Fermentation

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Questions and Answers

The main ingredients for brewing beer include water, grains, hops, and ______.

yeast

Soft water is best suited for brewing pale lagers with a good hop ______.

character

The hardness of water is determined by the amount of dissolved calcium and ______.

magnesium

Calcium Chloride is used to deliver a fuller body and a ______ finish to beer.

sweeter Signup and view all the answers

Dark beers, such as stouts, are typically brewed with ______ malt.

dark roasted Signup and view all the answers

During the boil, hops are added to impart ______ to the beer.

bitterness Signup and view all the answers

Yeast used in brewing can be classified into two types: ale yeast for top fermentation and ______ yeast for bottom fermentation.

lager Signup and view all the answers

Adjuncts like rice, maize, and corn are added to beer to enhance flavor and ______.

sweetness Signup and view all the answers

Flavor is imparted by ______ and yeast secondary metabolites.

hops Signup and view all the answers

The process of crushing and grinding malt to release fermentable sugars is called ______.

milling Signup and view all the answers

During the malting process, enzymes break down starch into sugars, particularly ______ and maltotriose.

maltose Signup and view all the answers

The temperature range for α-amylase activity is typically between ______ °C.

60-75 Signup and view all the answers

In the lautering process, mash is separated towards wort and residual ______.

grain Signup and view all the answers

Boiling the wort helps to extract hop flavor and ______ proteins.

coagulate Signup and view all the answers

The fermentation process is initiated by adding ______ to the cooled wort.

yeast Signup and view all the answers

Sodium bisulfite is used to treat yeast cultures for ______.

inoculation Signup and view all the answers

During fermentation, yeast convert sugar into ______, CO2 and glycerol.

ethanol Signup and view all the answers

S.Cerevisiae is known as ______ fermenting yeast used for making ales.

top Signup and view all the answers

Beer is stored at 0°C for several weeks to precipitate ______, yeast, resin and other undesirable substances.

protein Signup and view all the answers

The beer becomes clear after unwanted substances like ______ and proteins have settled.

yeast Signup and view all the answers

The wort is boiled in the ______ kettle where hops and adjuncts are added.

wort Signup and view all the answers

Bitterness in beer comes from α-acids extracted from the ______ during the boil process.

hops Signup and view all the answers

After fermentation, beer is placed in a ______ for maturation.

quiller Signup and view all the answers

The colour of beer can be measured using a ______.

spectrophotometer Signup and view all the answers

Industrial microbiology has two aspects: production of microbial products and environmental roles of microbes via ______.

bioremediation Signup and view all the answers

Fermentation is a part of the ______ pathway, which is crucial for regenerating living cells.

glycolysis Signup and view all the answers

In the absence of O2, pyruvate is metabolized to ethanol and ______ during alcohol fermentation.

carbon dioxide Signup and view all the answers

Wild yeast can be found on and inside the husks and ______ of plants.

flowers Signup and view all the answers

The process of converting starches into simple sugars during brewing is known as ______.

mashing Signup and view all the answers

Ales are typically fermented at ______ temperatures compared to lagers.

hotter Signup and view all the answers

During fermentation, nutrients are oxidized by glycolysis and released electrons reduce NAD+ to ______.

NADH Signup and view all the answers

Brewing yeast can directly digest starch; the more complex the sugar, the less likely the yeast can use ______.

them Signup and view all the answers

Study Notes

Industrial Microbiology

Uses metabolic reactions to produce metabolites for products
Focuses on microbial product production and environmental roles like biomediation and biodegradation.
Microbes are efficient at producing large arrays of compounds, but in small amounts needed for their growth.

Fermentation

Breakdown and re-assembly of biochemicals by organisms under aerobic or anaerobic conditions
Essential part of the glycolysis pathway, vital for cell regeneration
Nutrients are oxidized by glycolysis, and released electrons reduce NAD+ to NADH

Fermentation Products

Waste products produced in the absence of oxygen (O2)
Needed to regenerate NAD+ in the absence of O2.
Pyruvate, produced during glycolysis, is metabolized into ethanol and carbon dioxide in alcoholic fermentation:
- C6H12O6 → 2C2H5OH + 2CO2 + 2ATP

Alcoholic Fermentation

Done by specific yeasts used in making alcoholic beverages.
Other types of fermentation:
- Distillation of alcoholic beverages (like Pistarea drinks)
- Fermentation of grapes for wine
- Fermentation of malted grains for beer

Yeast

Unicellular fungi that reproduce asexually by fission
Do not undergo true sexual reproduction
Common in nature, found on/inside plants (husks and flowers)
Causing decay of ripe fruits due to sugar consumption
Ethanol production by fermentative yeasts may have evolved to inhibit bacteria competing for resources in ripe fruits.

Alcohol Timeline

Developed from fruit-based drinks to mead and beer (honey)

Yeast Usage

Different yeasts have different capabilities, based on sugar complexity
Yeast uses more monosaccharides than trisaccharides
Brewing yeast can directly digest starch
During beer brewing, starches in barley are broken down into simple sugars through a process called mashing.

Beer Flavor

Combination of changes at the molecular level in raw materials:
- Grain
- Hops
- Yeast
- Malt
- Brewing Stages

Beer Ranges

Alcohol by Volume (ABV) ranges from 3.1% to 30.1%
Beers are classified as Ales or Lagers based on fermentation temperature:
- Ales: Fermented at higher temperatures
- Lagers: Fermented at lower temperatures
- Specific yeast strains are used for each type.

Ale Styles

Characterized as:
- Chocotastey
- Amber
- Complex
- Pale Ales
- Stout

Lager Styles

Characterized as:
- Crisp
- Smooth
- Popular
- Pilsner
- Marzen

Raw Materials

Main ingredients: Water, grains (primarily malted barley), hops, and yeast
Beers contain 3-8% (v/v) ethanol.

Water

Essential for brewing
Water makes up 90-95% of beer
Added to malt during mashing for enzyme activity
Mineral content in water is important during mashing
pH impacts enzyme activity
Regional water analysis influences beer flavor
Water type varies depending on the beer being brewed.

Water Hardness

Amount of dissolved calcium and magnesium in water
Higher mineral content makes water hard
Water softening reduces the concentration of calcium and magnesium
Soft water typically has a higher sodium chloride (NaCl) concentration, resulting in less calcium.

Common Salts in Brewing:

Calcium Sulfate (Gypsum): Used for a drier, clean finish, like in Pilsner Lagers. Increases hop bitterness, ideal for IPAs.
Calcium Chloride: Contributes to a fuller body and sweeter finish.
Magnesium Sulfate (Epsom Salt): Increases sulfate and magnesium content, essential for yeast metabolism. Promotes healthy yeast growth and fermentation.

Water Hardness and Beer Styles

Hard water is optimal for dark beers and stouts. The dark roasted malt contributes to higher pH, leading to a lower reduction in alkalinity.
Soft water is suitable for pale lagers with a prominent hop character. Brewing with hard water would result in a harsh and stringent taste.

Malts

Malted grains used in brewing
Includes barley, rice, sorghum, wheat, oats, malt, etc.
Source of starch (sugar) = Maltose
Contributes to flavor, sweetness, and color of the beer

Hops

Added during the boiling process
Belong to the Humulus lupulus family, specifically Cannabis sativa
Hop addition influences different aspects of the beer:
- Beginning of boil: Contributes bitterness
- End of boil: Contributes flavor and aroma
- Produces pungent and aromatic character
- Contains tannins, aiding in protein coagulation
- Contains d-resin and β-lean for flavor and mold prevention
- Contains pectin, which contributes to foam

Adjuncts

Additional ingredients besides the main raw materials
Includes rice, maize (corn), oats, wheat, barley
Also includes chocolate, nuts, spices, and extra sugars
Unfermented sugars like lactose are sometimes added to milk stouts.

Yeast

Two types are used in beer brewing:
- Ale yeast (Top fermenting) - Saccharomyces cerevisiae
- Lager yeast (Bottom fermenting) - Saccharomyces pastorianus
Primary metabolites produced during fermentation: Ethanol, CO2, and glycerol.

Flavor

Imparted by hops and secondary metabolites produced by yeast
Secondary metabolites can be good or bad:
- Bad: Aldehyde (green apple), Diacetyl (100 malt dix), DMS
- Good: Clove, Fruity (ester flavor)

Clarifying Agents

Include Irish moss, gelden, and polyclar.
Used to precipitate proteins and hop solids during the brewing process
Found in trace amounts in the finished beer.

Brewing Process

1. Malting and Milling

Milling: Crushing or grinding malt to reduce size and release fermentable sugars
Malting: Converting barley into malt used for brewing. Prepares fermentable mashes from cereal grains.

Air Process of Malting:

The process of producing enzymes to break down starch into sugar
Quian's starches are transformed by soaking and germination
This process converts the adron into algae and cooks it, making it ready for fermentation.

Enzymes in Malting:

α-amylase: Breaks down amylopectin (long) branches of starches, creating long sugars. Optimal temperature: 67°C - 73°C.
β-amylase: Breaks α-1,4 glucosidic bonds, degrading long chains into simple sugars. Optimal temperature: 55°C - 66°C.

Malting Steps:

Grains are steeped for 1-3 days
Cooled in humid air for germination (3-4 days)
Dried in a kiln for up to 17 days
Rest period of 3 weeks allows the grains to mature into malt.

2. Mashing and Wort Preparation

Mashing: Mixing milled malt with water and heating for 2-3 hours in a mash tun. Enzymes digest starches and liberate sugars.
Most abundant sugars found in wort: Maltose, maltotriose, glucose, sucrose, isomaltose.
Other sugars identified: Isomaltose.

Lauterning

The process of separating the mash into wort and residual grain.
Residual grain is sparged with warm water to extract remaining sugars.

Wort Flavor:

Wort is flavored during the boiling process in a wort kettle.

Reasons for Wort Boiling:

Extraction of hop flavor and aroma
Coagulation of remaining protein and partial hydrolysis
Deactivation of enzymes active during mashing
Caramelization of sugars
Intensification of maillard reactions (reducing sugars and amino acids)
Sterilization and concentration of the wort.

3. Yeast Fermentation

Wort is cooled and yeast is added
Yeast cultures for inoculation are usually recovered from previous fermentation tanks using treatments like:
- Sodium bisulfite
- Tartaric acid
- Ammonium per sulfate
These treatments reduce pH and eliminate bacterial contamination.
Fermentation lasts for approximately 14 days.
During fermentation, yeast converts sugars into ethanol, CO2, and glycerol.
Secondary metabolites and diacetyl are also produced.
After 14 days, CO2 production ceases as the yeast cells become inactive.

Yeast Types in Beer Production

Saccharomyces cerevisiae (Top fermenting yeast) - Ales
Saccharomyces pastorianus (Bottom fermenting yeast) - Lagers.

4. Post Fermentation

Beer is stored at 0°C for several weeks
This process precipitates protein, yeast, resin, and other undesirable substances.
Resulting in a clear beer
Esters are also produced which contribute to flavor and aroma.

Post - Fermentation

After aging, the beer is carbonated with CO2
Then cooled, sanitized, and packaged into bottles.

SAB Process

The process of producing beer at South African Breweries (SAB).

Wort Production:

1. Milling: Malt is mashed in tuns for 2 hours to activate enzymes.
1. Lauter Tuns: Malt grains are processed, and wort is held.
1. Wort Kettle: Wort is boiled, and hops and adjuncts are added.
1. Whirlpool Kettle: Wort is rapidly spun to settle hops at the bottom. It is held for 20-30 minutes for hop flavor.
1. Separation: The wort is pumped out for separation.

Fermentation:

Wort is placed into large fermentation vessels with cooling jackets
Fermentation lasts 12 days at 14°C (Black Label: 15.8°C)

Maturation:

After fermentation, beer is transferred to a quiller.

Filtration:

Kieselguhr candle filters (diatomaceous earth) are used to clarify beer.
Removes any residual yeast and trub.

Bottling:

Beer is transferred to a bright beer tank.
Concentrated to the correct volume.
Carbonated before bottling and capping.

Beer Analysis

Colour

Measured using a spectrophotometer.
Standard Reference Method (SRM) measures color intensity.
SRM Formula: 12.7 x DX A430 (LoG)

International Bitterness Units (IBU)

Bitterness originates from α-acids extracted from hops during the boil.
IBU reflects the type of hops used and when they were added.
IBU Formula: 184 x A75nm x 47.

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Description

This quiz explores the critical concepts of industrial microbiology, focusing on microbial product production and fermentation processes. It covers the metabolic reactions involved in producing various compounds, especially under aerobic and anaerobic conditions. Test your knowledge on fermentation products and their significance in biochemistry.