Podcast
Questions and Answers
The main ingredients for brewing beer include water, grains, hops, and ______.
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 ______.
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 ______.
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.
Calcium Chloride is used to deliver a fuller body and a ______ finish to beer.
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Dark beers, such as stouts, are typically brewed with ______ malt.
Dark beers, such as stouts, are typically brewed with ______ malt.
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During the boil, hops are added to impart ______ to the beer.
During the boil, hops are added to impart ______ to the beer.
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Yeast used in brewing can be classified into two types: ale yeast for top fermentation and ______ yeast for bottom fermentation.
Yeast used in brewing can be classified into two types: ale yeast for top fermentation and ______ yeast for bottom fermentation.
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Adjuncts like rice, maize, and corn are added to beer to enhance flavor and ______.
Adjuncts like rice, maize, and corn are added to beer to enhance flavor and ______.
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Flavor is imparted by ______ and yeast secondary metabolites.
Flavor is imparted by ______ and yeast secondary metabolites.
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The process of crushing and grinding malt to release fermentable sugars is called ______.
The process of crushing and grinding malt to release fermentable sugars is called ______.
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During the malting process, enzymes break down starch into sugars, particularly ______ and maltotriose.
During the malting process, enzymes break down starch into sugars, particularly ______ and maltotriose.
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The temperature range for α-amylase activity is typically between ______ °C.
The temperature range for α-amylase activity is typically between ______ °C.
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In the lautering process, mash is separated towards wort and residual ______.
In the lautering process, mash is separated towards wort and residual ______.
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Boiling the wort helps to extract hop flavor and ______ proteins.
Boiling the wort helps to extract hop flavor and ______ proteins.
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The fermentation process is initiated by adding ______ to the cooled wort.
The fermentation process is initiated by adding ______ to the cooled wort.
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Sodium bisulfite is used to treat yeast cultures for ______.
Sodium bisulfite is used to treat yeast cultures for ______.
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During fermentation, yeast convert sugar into ______, CO2 and glycerol.
During fermentation, yeast convert sugar into ______, CO2 and glycerol.
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S.Cerevisiae is known as ______ fermenting yeast used for making ales.
S.Cerevisiae is known as ______ fermenting yeast used for making ales.
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Beer is stored at 0°C for several weeks to precipitate ______, yeast, resin and other undesirable substances.
Beer is stored at 0°C for several weeks to precipitate ______, yeast, resin and other undesirable substances.
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The beer becomes clear after unwanted substances like ______ and proteins have settled.
The beer becomes clear after unwanted substances like ______ and proteins have settled.
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The wort is boiled in the ______ kettle where hops and adjuncts are added.
The wort is boiled in the ______ kettle where hops and adjuncts are added.
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Bitterness in beer comes from α-acids extracted from the ______ during the boil process.
Bitterness in beer comes from α-acids extracted from the ______ during the boil process.
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After fermentation, beer is placed in a ______ for maturation.
After fermentation, beer is placed in a ______ for maturation.
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The colour of beer can be measured using a ______.
The colour of beer can be measured using a ______.
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Industrial microbiology has two aspects: production of microbial products and environmental roles of microbes via ______.
Industrial microbiology has two aspects: production of microbial products and environmental roles of microbes via ______.
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Fermentation is a part of the ______ pathway, which is crucial for regenerating living cells.
Fermentation is a part of the ______ pathway, which is crucial for regenerating living cells.
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In the absence of O2, pyruvate is metabolized to ethanol and ______ during alcohol fermentation.
In the absence of O2, pyruvate is metabolized to ethanol and ______ during alcohol fermentation.
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Wild yeast can be found on and inside the husks and ______ of plants.
Wild yeast can be found on and inside the husks and ______ of plants.
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The process of converting starches into simple sugars during brewing is known as ______.
The process of converting starches into simple sugars during brewing is known as ______.
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Ales are typically fermented at ______ temperatures compared to lagers.
Ales are typically fermented at ______ temperatures compared to lagers.
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During fermentation, nutrients are oxidized by glycolysis and released electrons reduce NAD+ to ______.
During fermentation, nutrients are oxidized by glycolysis and released electrons reduce NAD+ to ______.
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Brewing yeast can directly digest starch; the more complex the sugar, the less likely the yeast can use ______.
Brewing yeast can directly digest starch; the more complex the sugar, the less likely the yeast can use ______.
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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:
-
- Milling: Malt is mashed in tuns for 2 hours to activate enzymes.
-
- Lauter Tuns: Malt grains are processed, and wort is held.
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- Wort Kettle: Wort is boiled, and hops and adjuncts are added.
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- Whirlpool Kettle: Wort is rapidly spun to settle hops at the bottom. It is held for 20-30 minutes for hop flavor.
-
- 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.
