In the brewing process of beer equipment, the invasion of foreign microorganisms is inevitable. These microorganisms grow and reproduce using the wort or nutrients in beer, which can lead to difficulties or abnormalities in subsequent production, precipitation of the finished beer, and even variations in flavor and taste due to their metabolites.
Beer Saccharification stage:
Susceptible bacteria species: thermophilic Lactobacillus
Note: At the beginning of saccharification, when the mash temperature is less than or equal to 50°C, dyeing is easy but beneficial for reducing the mash pH. Above 50°C, lactobacillus does not easily grow.
The wort is cooled before inoculation:
Susceptible bacteria species: coliform, wild yeast, lactobacillus, micrococcus, bacillus subtilis, mold, actinomycetes, Flavobacterium mutans, etc.
Note: It can still grow at 40°C, so it is important to prevent unclean water from mixing into the wort. These bacteria can multiply millions of times within 7 hours. They often lurk in gaps, threads, and debris, entering the wort through the flow or from reused yeast.
When contaminated by yeast, they compete with yeast for reproduction and cease growth before fermentation is complete. Acetobacter and lactobacillus grow slowly in contaminated wort. Dead corners in the thin plate system, poor hygiene, incomplete sterilization, and contamination of the sterile air system can also contribute to bacterial growth.
Fermentation stage:
Susceptible bacteria species: Lactobacillus, Acetobacter, wild yeast, football bacteria, Flavobacterium mutans.
Description: Common system hygiene brushing and inadequate sterilization during yeast inoculation process. Polluted yeast grows and reproduces abundantly during fermentation. Open fermentation favors the growth of acetic acid bacteria, while closed fermentation favors the growth of lactic acid bacteria.
Beer storage stage:
Susceptible bacteria species: Acetobacter, Lactobacillus, Zymomonas, Coliform
Description: Inadequate cleaning and sterilization of fermentation tanks, wine storage tanks, brite tanks, and beer filter systems during beer serving. Bacteria breed quickly when there is air in the upper part of the beer or wine, and they grow under anaerobic conditions.
Beer Packaging stage:
Susceptible bacteria species: Acetobacter, Lactobacillus, football bacteria, Zymomonas, Coliform, mold
Description: During the packaging process, the packaging and conveying system, filling machine’s beer tank, empty bottles, and empty barrels become heavily contaminated. Not all microorganisms entering the brewing process are harmful to beer. They can be divided into two categories based on their harm: harmless symbiotic bacteria/harmful bacteria.
Harmless symbiotic bacteria include mold spores and many aerobic bacteria that cannot grow in beer, as the beer environment suffocates them. However, the presence of these microorganisms indicates the potential presence of harmful microorganisms.
The so-called relatively harmless microorganisms for beer are those that do not cause turbidity and haze in beer brewing, such as certain good spore bacteria.
Harmful bacteria refer to human pathogens (like coliform bacteria) or microorganisms that grow and multiply under specific conditions, causing abnormal beer production processes, rancidity, staleness, viscosity, precipitation, and cloudiness. Examples of harmful bacteria species include wild yeast, Lactobacillus, Streptococcus, Pectinobacter, Megacoccus, and Enterobacteriaceae.
