Think the reasons for the abnormally sour taste of beer can be divided into two categories:
One is abiotic acidity: that is, the acidity produced by non-biological fermentation, such as the acidity produced by water quality, water quality regulator, and malt;
One is biological sourness: that is, it is infected with acid-producing bacteria such as lactic acid bacteria or acetic acid bacteria.
Let’s analyze the reasons in detail and what precautions should be taken during the brewing process:
When brewing beer, water with different hardness and ion content should be selected according to the characteristics of beer. If making wheat wine, the calcium and magnesium ions of non-carbonate hardness in the water should not be too high because calcium sulfate, magnesium sulfate, and dipotassium hydrogen phosphate react to generate acidic potassium dihydrogen phosphate, which increases the acidity of the mash and wort.
A simple way to distinguish carbonate hardness and non-carbonate hardness is by observing how they form scale when boiled. If there is a lot of scale, it indicates higher bicarbonate hardness, whereas non-carbonate hardness may be higher.
In addition, pure water is not recommended for brewing wheat beer because it has a low pH.
Water quality has a great influence on the flavor of beer, so it is recommended to have the water quality tested and analyzed by a professional organization before brewing to formulate the corresponding saccharification process.
Water quality adjustment
When adjusting water for saccharification, the amount of calcium sulfate or magnesium chloride added should be determined according to the water quality indicators. Incorrect or excessive use will increase the acidity of the wort.
The acidity of malt is generally expressed by pH value. The pH value of basic malt (such as light Australian wheat) is generally around 5.9. Wheat malt has a lower pH and higher acidity compared to light Australian wheat. Therefore, wheat beer has a slightly sour taste compared to pilsner pale beer.
If the selected malt has higher acidity, it will inevitably affect the taste of the beer. Therefore, when buying malt, it is important to clarify the requirements for the indicators, the type of beer to be made, and the appropriate malt to choose.
If the beer brewing system is contaminated with bacteria such as lactic acid bacteria or acetic acid bacteria, it is difficult to completely remove them. It is similar to the new coronavirus, where you don’t know where it hides. Therefore, each time the beer brewing equipment is cleaned and disinfected, one should not have the mentality of “I will completely kill it next time”. Here is an analysis of the links that are more likely to contaminate bacteria such as lactic acid bacteria:
Cooling of mashed wort sheet and subsequent pipeline
After each mash sheet is used, if it cannot be thoroughly cleaned and disinfected, the cooled wort residue becomes a suitable environment for bacteria such as lactic acid bacteria to grow due to its rich nutrients. If necessary, the mash sheet needs to be disassembled for cleaning and descaling.
The sanitary condition of the yeast determines whether it can be propagated. Before connecting the cold wort to the yeast, a microscopic examination should be conducted to check the hygiene of the yeast. If there are bacteria such as bacilli present, it should not be passed.
Beer filling has the highest hygiene requirements in the brewing process. It belongs to the clean operation area. Attention should be paid to sterilization and disinfection of the space, containers, and contact surfaces. What is often overlooked is the packaging container used, such as cans, which many people think do not provide a nutrient medium for bacteria to grow. However, after conducting microbial smear tests, it is found that if stored in a poor environment for a long time, contamination can still occur. This is especially important when making fresh beer.
According to long-term production experience and sanitation testing results, personnel are one of the main sources of lactic acid bacteria contamination. Especially after April every year, when the weather gets warmer, if operators do not regularly wash their hands and disinfect (normally at least once an hour, and wash hands and disinfect anytime they touch unclean surfaces), a large number of lactic acid bacteria will grow and be introduced into the beer, especially through manual operations in the brewery.
There are many reasons for the sourness of beer, which need to be systematically analyzed from various aspects such as manpower, equipment, materials, methods, environment, and measurements. Comprehensive prevention and control measures should be adopted.
The quality of beer follows the principle of “three parts craftsmanship, seven parts hygiene”. When hygiene is done well, the taste is pure. As brewers, we should prioritize practicing good hygiene.