Beer Fermentation Tank: The Complete Guide to Stainless steel Beer fermentation Tanks for Commercial Stainless Steel Beer Brewing Tanks

Beer Fermentation

Beer fermentation is a complex biochemical and material transformation process.

Primary Yeast Metabolites and Fermentation By-products

· Ethanol and carbon dioxide

· Higher alcohols, aldehydes, organic acids, esters, ketones and sulfur-containing compounds

These fermentation products determine the physicochemical properties of beer, including flavour, foam, colour and stability, and deliver the beer’s characteristic sensory profile.

Types of Fermentation

Based on the yeast strain used, beer fermentation is classified into top fermentation and bottom fermentation:

· Top-fermented beer: uses top-cropping yeast with a higher fermentation temperature of 16–22°C

· Bottom-fermented beer: uses bottom-cropping yeast with a lower fermentation temperature of 7–12°C

Fermentation Process

The overall fermentation process is broadly divided into three stages: 

(1) Yeast adaptation phase 

(2) Aerobic respiration phase 

(3) Anaerobic fermentation phase

Fermentation is a continuous process; the material transformations during primary fermentation and secondary fermentation form an interconnected system. 

During fermentation, yeast metabolism generates various by-products, some of which are subsequently degraded. The formation and partial breakdown of these by-products are tightly linked to yeast metabolism.

Ethanol Production via Glucose Fermentation

The biochemical mechanism of alcoholic fermentation from glucose is the fundamental theory for alcohol production and brewing. For beer brewing, ethanol and carbon dioxide are key beer components. In addition, the Embden–Meyerhof–Parnas (EMP) glycolytic pathway forms the basis for synthesising many flavour metabolites.

Carbohydrate Metabolism

Wort is nutrient-rich and provides a favourable habitat for yeast cells. Yeast assimilates nutrients from wort and excretes metabolites. Carbohydrates account for approximately 90% of the total wort extract. Glucose, fructose, sucrose, maltose, maltotriose and raffinose are fermentable sugars. They serve as the primary carbon source for brewer’s yeast and the core carbon substrate during fermentation.

DP9–DP12 dextrins, maltotetraose, maltopentaose through maltononaose present in wort are non-fermentable sugars, also referred to as non-sugars. In commercial production, the ratio of fermentable sugars to non-sugars is typically controlled at 7:3.

· Light refreshing beer: moderately higher proportion of fermentable sugars, high degree of fermentation and crisp taste

· Full-bodied beer: moderately higher proportion of non-sugars to enhance mouthfeel and body

Degree of Fermentation

The percentage reduction in beer extract is defined as the degree of fermentation. Residual sugar content and fermentation degree vary across beer styles. During beer fermentation, sugars are continuously consumed and the beer extract concentration declines accordingly. The concept of fermentation degree was introduced to precisely quantify the fermented fraction of wort extract, denoted by the symbol V. Fermented extract = Extract content of inoculated wort − Extract content of beer at the time of measurement

Apparent Degree of Fermentation (Vs)

During primary fermentation, extract concentration is measured with a refractometer / saccharimeter. The fermentation degree converted from this reading is the apparent degree of fermentation, which deviates from the real degree of fermentation. This deviation is proportional to the fermentation degree, and apparent extract measurement is straightforward, so breweries rely on apparent fermentation degree for process control.

· Apparent fermentation degree for pale beer: generally 68–75%

· Apparent fermentation degree for dark beer and strong beer: generally 64–73%

Real Degree of Fermentation (Vω)

First, all ethanol is distilled from the test beer sample; water is then added to restore the original volume before measuring the concentration. This value is the real extract concentration, and the fermentation degree calculated from it is the real degree of fermentation, representing the percentage of extract consumed during fermentation. Ethanol and CO₂ in the sample lower the liquid specific gravity, causing the measured apparent sugar reading to understate the true extract content. For this reason, the real fermentation degree is always lower than the apparent fermentation degree; the apparent value is normally around 20% higher. Simplified conversion formula: \(\boldsymbol{V_ω≈0.819V_S}\) The coefficient 0.819 is an empirical constant derived by Balling in 1870.

Terminal Degree of Fermentation (EV)

To establish a benchmark for fermentation performance, the proportion of fermentable substances within the total extract must be determined — this is the terminal degree of fermentation. From wort pitching through to packaging, extract loss proceeds unevenly: the rate of extract consumption in primary fermentation is far higher than in secondary fermentation.