Craft Beer Production: Ingredients, Brewing, and Fermentation

Posted on Jan 14, 2025 in Chemistry

Ingredients

  • Water: Essential for all stages of brewing.
  • Malt: Typically barley, steeped, germinated, and dried to provide sugars.
  • Adjuncts: Maize grits, corn syrup, rice, beet, or cane sugar. These can lighten the beer’s flavor or color.
  • Hops: Provide bitterness, aroma, and inhibit bacterial growth.
  • Yeast: Converts sugar into CO2, alcohol, and flavors.

Brewing Process

  1. Brewhouse

    • Raw Material Preparation: Malt is milled, keeping husks intact if desired. The kernel is milled to small, uniform particles, minimizing flour.
    • Mashing: Water and malt are agitated in the mash kettle. Mash out occurs when starch converts to sugar and proteins break down.
    • Malt Filtration: The mash is transferred, the wort is moved to the kettle, and sparging occurs to separate the wort from the spent grains.
    • Wort Kettle: Enzymes are destroyed, the wort is sterilized, hops are extracted, the wort is colored and concentrated, and undesirable aromas are removed.
    • Whirlpool and Wort Cooling: Trub is separated from the wort, and the wort is cooled to fermentation temperature (18-24°C for ale, 10-18°C for lager).

  2. Fermentation

    • Oxygenation and yeast injection.
    • Growth phase and cooling for maturation.
    • Ale Beers: Top-fermenting yeast, warmer fermentation (18-24°C).
    • Lager Beers: Bottom-fermenting yeast, cooler fermentation (10-18°C).
    • Yeast products: alcohol, CO2, diacetyl.

  3. Maturation/Aging

    • Cooling in the fermenter, centrifuging, maturation at 4°C, and aging in tanks (0 to -2°C).

  4. Filtration

    • Removes yeast cells to increase shelf life.
    • Uses various filters: sheet, candle, screen, leaf, chamber, and membrane.
    • Factors affecting filterability: malt quality, wort viscosity, and pH.

Malt Production

  1. Barley Precleaner: Separates impurities like weed seeds and broken barley.
  2. Malt Cleaning: Removes rootlets.
  3. Pilsner Malt Composition: Water 8.8%, Protein 30.0%, Fat 2.0%, Ash 6.0%, Fiber 8.6%, Non-nitrogenous extract 44.6%.
  4. Malt Polishing: Cleans malt from small particles before dispatch.
  5. Malt Evaluation: Hand, mechanical, and chemical-technological methods.

Mashing In

Mixing grist with water at a specific temperature. The grist-to-water ratio is crucial for first wort running. The mash is 5-6% stronger than the beer’s original gravity. For pale beer, use 3-5 hl of water/100 kg grist; for dark beers, 3-4 hl water/100 kg malt. The volume of grist mashed is 0.7-1 hl/100 kg malt grist.

During mashing, malt content is brought into solution, and enzymes extract it. Enzymes break chemical bonds in substrates. Starch degradation occurs in three stages: gelatinization, liquefaction, and saccharification.

Mashing can be:

  • Infusion: Simple, using one vessel. The mash is heated slowly to the rest temperature.
  • Decoction: Uses two vessels. 1/3 of the mash is boiled, then mixed back with the rest.

Rest Temperatures During Mashing:

  • 45-48°C: Protein and beta-glucanase rest.
  • 62-65°C: Maltose production rest.
  • 70-72°C: Saccharification rest.
  • 75-78°C: Final mash temperature.

Lautering/Filtration

Separates the solid phase (spent grains) from the liquid phase (wort). The spent grains act as a filter. This process occurs in the lauter tun in two stages:

  1. Pumping mash to the lauter tun.
  2. Sedimentation of the solid phase.
  3. Circulation of haze wort until clear.
  4. Running off.
  5. Cutting of the layer of spent grains when necessary.
  6. Sparging with hot water.
  7. Mixing sparge water with spent grains.

Sparging leaches remaining sugar from spent grains using hot water (75-78°C) until the extract content is below 1%.

Operating Sequence of Mash Filter:

  1. Filling the filter.
  2. Filtering the mash, running off the first wort.
  3. First compression.
  4. Sparging.
  5. Final compression.
  6. Spent grain discharge.

Fermentation Cellar Yield

Measures volume and extract content upon arrival in the fermentation cellar. Cold wort volume is calculated using: V1 = V0 x CF, where V1 is the volume after cooling, V0 is the volume before cooling, and CF is the contraction factor (0.96).

Pitching

Adding yeast to the cold, aerated wort to start fermentation. Insufficient aeration can cause defective fermentation, longer fermentation times, cessation of extract removal, and beer quality problems.

Degree of Attenuation

The extent of conversion to alcohol. Calculated as: Vs = (Eo – Ef) x 100 / Eo, where Vs is the fermented extract, Eo is the original extract, and Ef is the final extract.

Fermentation of Wort

Yeast obtains energy through respiration (aerobic) or fermentation (anaerobic). During fermentation, yeast converts sugar to alcohol and CO2. Saccharomyces cerevisiae is used for top-fermenting beers, and Saccharomyces carlsbergensis for bottom-fermenting beers.

Fermentation Steps

  1. The fermenting wort is covered by a white layer of fine bubbles.
  2. The fine bubble foam becomes deeper with brown caps.
  3. High krausen: Fermentation is most intensive, with higher crests and coarser bubbles.
  4. Krausen collapsing: Fermentation slows, and the crests collapse.
  5. Collapsed foam: The foam forms a loose, dirty brown layer, removed before pumping to a larger tank.

Fermentation in CCT: 10°C to 4°C. Maturation (lager process) in CCT: -1°C to 2.5°C.

Running Off of the First Wort

First wort should run off quickly. It passes through the spent grains and is filtered. The spent grains cause a suction effect, compressing the layer of spent grains. The operation of rakes is controlled by the pressure difference.

Sparging

After running off the first wort, spent grains are leached with hot water (78°C). Sparging can be continuous (quicker but lower yield) or in separate sparges. Continuous sparging offers clear lautering, less husk leaching, less oxygen uptake, shorter process time, and better flavor stability.

Spent Grains Removal

After the last sparging, the rakes are set at right angles, or a pushing beam is lowered to push spent grains out of the lauter tun.

Lauter Tun Process Time

  • Water supply: 5 mins
  • Filling: 10 mins
  • Drawing off and pumping off of cloudy wort: 5 mins
  • First wort: 40 mins
  • Sparging water: 40 mins
  • Emptying: 3 mins
  • Removal of spent grains: 10 mins
  • Rinsing of false bottom: 2 mins
  • Emptying: 5 mins
  • Total time: 120 mins