Lecture: Biotechnology of Beer Brewing

Question-and-answer flashcards covering ingredients, biochemical steps, equipment, yeast physiology, process stages, by-products and modern variations such as low-alcohol brewing.

What four core ingredients are found in every traditional beer?

Water, hops, malt (malted barley) and yeast

Which 1516 German law restricts beer ingredients to only water, hops, malt and yeast?

The Reinheitsgebot (German Beer Purity Law)

Besides the four core ingredients, what are ‘adjuncts’ in brewing?

Extra fermentable sugars such as rice, corn or cane sugar added to the wort

Name two non-traditional additions sometimes used in Belgian beers.

Fruits and herbs

What gives beer its characteristic bitterness and many floral aromas?

Hop compounds extracted during the wort boil

Why are hops considered antimicrobial?

Hop acids inhibit the growth of many spoilage bacteria, extending beer’s shelf life

List three visible appearance features that distinguish beer.

Carbonation, a foaming head, and colour ranging from pale amber to very dark

Is cloudiness always a sign of spoiled beer?

No; protein haze or residual yeast can intentionally give certain beers a cloudy look

Which country currently drinks the most beer per capita?

The Czech Republic

Which country produces the largest total volume of beer?

China

Roughly how large is the global beer market in US dollars?

Over 700 billion dollars

What two main yeast categories are used in brewing?

Ale yeasts (top-fermenting) and lager yeasts (bottom-fermenting)

What is ‘wort’ in brewing terminology?

The sweet, hopped liquid derived from malt that is fermented into beer

Which three key enzyme groups originate from malted grain?

Amylases, proteases and β-glucanases

What does amylase do during mashing?

Converts starches into fermentable sugars such as glucose and maltose

What is the purpose of proteases in the mash?

Hydrolyse grain proteins into peptides and amino acids for yeast nutrition and haze reduction

Why are β-glucanases useful in brewing?

They break down cell-wall glucans, improving mash filterability and sugar yield

List the three stages of commercial malting.

Steeping, germination (3–5 days) and kilning

Why must dark and light malts be blended, not brewed with dark malt alone?

High-kiln temperatures that create dark malt inactivate many essential malt enzymes

What is the first mechanical step performed on malt inside the brewery?

Milling (cracking the husk to expose the starch)

What is ‘mashing’?

Mixing milled malt (and adjuncts) with water under a controlled temperature profile to activate malt enzymes

At which temperature range are proteases and β-glucanases most active during mashing?

Lower temperatures (around 45–55 °C)

At which temperature range are amylases most active?

Higher mash rests (60–70 °C)

What vessel separates sweet wort from spent grain solids?

A lauter tun (or mash filter)

Name three functions of the wort-boil kettle.

Sterilises wort, denatures unwanted proteins, and extracts hop bitterness/aroma compounds

When are bittering hops typically added during the boil?

Early in the boil

When are aroma hops usually added?

Late in the boil, to preserve volatile floral compounds

What is the ‘whirlpool’ used for?

Settling and concentrating hot trub solids in the centre, allowing clarified wort to be drawn off

Why is oxygen deliberately introduced only at the start of fermentation?

Yeast need a small amount of O₂ for sterol synthesis, but later oxygen causes beer oxidation and flavour staling

What traditional term describes adding yeast to the cooled wort?

Pitching the yeast

Describe the classic shape of a modern lager fermenter and its purpose.

Cylindro-conical; the cone collects flocculated yeast for easy harvest while CO₂ lift provides gentle circulation

Which sugars disappear first during fermentation: glucose, maltose or maltotriose?

Glucose (and other monosaccharides) are consumed first, followed by maltose, with maltotriose last and sometimes incomplete

What three valuable by-products leave the fermenter besides beer?

Food-grade CO₂, surplus yeast (for yeast extract/Vegemite), and spent grain (animal feed)

How does residual non-fermentable sugar affect finished beer?

It adds body, mouthfeel and calorie content

What two main downstream options prepare beer for sale?

Filtration/clarification and pasteurisation (either in-package or inline)

Why are many beers packaged in brown or green bottles?

To protect hop compounds from light-induced off-flavour reactions

Explain the difference between pasteurisation and sterilisation in brewing.

Pasteurisation reduces microbial load; sterilisation would eliminate all organisms (rarely done for beer)

What is ‘high-gravity’ brewing?

Fermenting a high-sugar wort to produce strong beer that is later diluted with carbonated water

Give two water-treatment steps commonly performed before brewing.

Adjust hardness with Ca²⁺/Mg²⁺ salts and UV filtration/sterilisation

Name four stresses a brewing yeast must tolerate.

Low pH, ethanol presence, limited oxygen after the start, and cool fermentation temperatures

What are two common physical processes for producing 0-alcohol or low-alcohol beer?

Vacuum distillation and reverse osmosis

State two biological strategies for brewing low-alcohol beer.

Using yeast strains that produce little ethanol or reducing fermentable sugar content in the wort

Why is CO₂ from fermentation labelled ‘food grade’?

It originates from a controlled food process, free from industrial contaminants, and can be reused for beverage dispensing

What practical reason led early Europeans to favour hopped beer?

Hop’s antibacterial effect extended beer’s shelf life compared with other herbal ales

In a mash temperature profile, what physical change is described as ‘gelatinisation’?

Starch granules swell and become soluble, making them accessible to amylase cleavage

Why is filtration of beer sometimes intentionally skipped (e.g., in some craft styles)?

To retain yeast haze and proteins, giving specific flavour and mouthfeel characteristics (e.g., hefeweizen)