Quality Control and Common Problems in Beer Brewing

Beer is produced from natural raw materials through a series of physical, chemical and biological logical processes. There are a lot of variables in raw materials and at each stage of the brewing process, so breweries must use sound judgment and appropriate techniques to ensure that beer is produced to specification and without failure. However, this is not always foolproof, and a range of problems can arise when brewing beer. When a problem is discovered, it is necessary to clarify the original meaning of the problem, so that the problem can be corrected and prevented in advance.

To avoid problems with the final finished beer, every raw material and every stage of the brewing process needs to be measured and recorded. It is necessary to invest in some basic testing equipment in order to detect problems in time. The most basic is a microscope and a pH meter for daily monitoring of the product and the brewing process. It is also possible to send wort and beer to an external laboratory for testing, but with the expansion of the brewery, it is relatively more cost-effective to set up its own laboratory in the factory.

Commonly Used Detection Tools

Spectrophotometers are used to measure color and bitterness; turbidimeters are used to determine haze; quality is ensured by monitoring oxygen and carbon dioxide levels in packaged beer; only media, petri dishes, and plastic inoculating loops are required to operate some basic Microbial Detection. A pressure cooker can be used as its autoclave. Although the optimal environment for cultivation is a small incubator at 25°C/77°F, usually cultures can also be incubated at room temperature. The ATP test can be used to quickly and non-specifically show the presence of microorganisms. The tank walls can be wiped and rinsed with water tested to determine the level of ATP (which only contains what is found in all living cells). The final result can be used to determine, for example, whether a container is ready for use or needs further cleaning.

With the help of the right monitoring program, potential problems can be detected in the production process in time and remedied before filling.

Quality Control Of Raw Materials Is The First Link In Beer Brewing

Brewing water is one of the final sources of off-flavor and turbidity. Excess mineral content can adversely affect mashing, boiling and fermentation processes. The minerals themselves, as well as any contaminants in the water, can also be present directly in the bottled beer, adversely affecting the taste. The mineral content of the water should be tested at least annually and every time the source of the water supply is changed. Most breweries send water samples to outside labs for testing, but a simple inspection of useful information can be done by the brewery itself.

The pH of the brewing water can well show the changes in its mineral composition, suggesting that if the water source changes, the treatment during brewing should be adjusted. Chemicals used in water treatment, especially those containing chlorine groups, can very easily cause problems with beer, but their strong odor also makes them easy to detect in water.

Each batch of malt should be evaluated as it arrives and the analysis checked against the specifications required for each malt type. The extract and moisture content will determine how the recipe can be adjusted so that the wort has the same initial gravity. High protein content may present potential turbidity issues. The special colour of a particular malt species may mean that special treatment is required to ensure that the beer exhibits the correct colour. Visually inspect the malt for the presence of worms, foreign bodies or mold. Malt used in primary brewing is generally less likely to expire, but it should also be ensured that the correct batch is used. For special varieties of malt that are rarely used, the expiration date should be checked before each use. The inspection of other adjuvants (malt, carbohydrate sources other than barley) should be arranged with reference to the particular variety of malt.

Hops are also inspected upon arrival, adjusted if necessary to ensure consistent bitterness from the alpha acid content, and inspected for damage to the packaging and exposure to air. If the packaging is damaged, it needs to be checked visually and by smell for changes in quality. Because the hops are oxidized when exposed to air, they produce a cheese-like taste. Therefore, the opening date should also be recorded when using, and the use of hops that have been opened for too long should be avoided.

Dry yeast is also checked upon arrival and the batch number is recorded. If the packaging is soft, it is damaged and should be rejected or the supplier should be contacted. Wet yeast storage conditions (<4°C/39°F) require real-time monitoring. Yeast bottling should be less than a week old and use a microscope to check its viability and cell count before putting it into the fermenter.

The turbidity of the produced beer is the most common problem in the beer brewing process. While this turbidity is acceptable for some beer varieties, for most consumers, turbidity is always associated with hygiene issues.

The haze phenomenon in beer is caused by particles in suspension and colloidal state. These particles can be divided into microbial (i.e. caused by bacteria or yeast) and non-microbial. There are many types of non-microorganisms, but the most common cause of beer turbidity is protein-polyphenol complexes. Polyphenolic proteins are the major constituents of residues, hot flocs, cold flocs, refrigerated turbidity and some permanent hazes. Polyphenols can bind to proteins through covalent and non-covalent interactions, and when these complexes form particles large enough to precipitate, they cause turbidity.

How To Spot Turbidity Early

In order to avoid as far as possible cloudy beer entering the market, early warning can be obtained by monitoring the production process.

During the boiling stage, thermal flocs are formed due to the coagulation of proteins and polyphenols. After boiling, the wort is sampled and placed overnight to observe how many thermal fractures are formed and how clear the wort is. In the same way, the wort after cooling before adding yeast is sampled to detect the cold flocs contained in it. The total number of flocs formed can be measured using the conical tube, and the flocs formed and wort clarity can be recorded numerically or descriptively. But the sample left in the sampling bottle can also provide useful information: after settling overnight, the large flocs in the wort are hot flocs, and the fine sediments are cold flocs.

If the filtration process of the beer goes wrong, it is inevitable that yeast will be found in the bottled beer. Taking a sample of the filtered beer and using a microscope and a hemocytometer can measure the yeast count and figure out if it causes turbidity. For barrel beer, the acceptable yeast count is 520,000 cells per milliliter. This standard also applies to bottled beer. If the beer concentration is higher, this number will be higher. It’s a good idea for breweries to keep a test barrel for each batch of beer in order to assess its turbidity and carbonation. For beer with a longer shelf life, it is recommended to use a turbidimeter for more complex and professional turbidity analysis.

How To Avoid Turbidity

The main source of abiotic particles is malt, but many other factors at different stages of the brewing process can trigger their formation.

This starts with the first step in the brewing process, as the mineral content of the brewing water is essential to prevent cloudiness. The calcium content in brewing water should be greater than 100mg/L, and the alkalinity of carbonate should be less than 50mg/L. Calcium has the effect of lowering the pH of the mash, while carbonates raise the pH. The optimal pH value of the wort should be kept at 5.2-5.3. If the pH value is too high, more polyphenols will be extracted from the malt during the mashing process, and the beer may be cloudy. For small breweries only, the most common way to remove carbonates is to add food-grade acid in a hot water tank, while calcium salts are mixed evenly into the ground malt before mashing and stirring. A word of caution: the choice of acid and salt is likely to affect the chloride/sulfate ratio in the beer, which in turn has an effect on flavor (sulfates add bitterness, chlorides add sweetness).

The protein component of non-biological particles comes from malt, and if the total nitrogen content in the raw material exceeds 1.65%, turbidity is more likely to occur. The protein content can be reduced by composing some extracts with a percentage of low-protein supplements such as sugar or rice. Or choose malt made from barley varieties that have had their polyphenol procyanidins removed.

Vigorous boiling promotes the formation of hot flocs, which can be removed like hop residue. The polysaccharides extracted from seaweed should be put into the wort after boiling as a clarifying agent, which can promote the formation of cold flocs and help to remove the polyphenolic proteins formed later. The addition of the clarifying agent is not arbitrary, and the use of too much or too little will have an adverse effect on the clarifying effect.

The polyphenols in hops are also extracted during the boiling process and produce non-biological particles, especially in beer varieties that require too much hops.

During the saccharification process, when the starch in the mash is not completely converted, the starch can also lead to turbidity. So the mashing process lasts at least an hour at a temperature of 63°-68°C (145.5-154.5°F), and a simple iodine test before wort filtration confirms that the starch has been converted sufficiently.

Other Sources Of Non-Biological Particle Formation Include

• If the β-glucan in malt is too high, you need to change the malt variety, or add β-glucanase to the mash.

• There is not enough calcium in the mash to allow it to settle early in the brewing process.

• Metal ion contamination from pipes, containers or water supplies.

The source of microbial particles may be yeast cells or bacterial/wild yeast infections that were not thoroughly isolated in suspension. Good flocculation can separate yeast from suspension.

Calcium is required for yeast flocculation, and both auxiliary clarifiers and isinglass clarifiers are helpful for beer clarification. Adding an auxiliary clarifier to the isinglass clarifier and using it before it (eg in a fermenter) can help the isinglass clarifier to work better. Isinglass clarifiers have a positive charge that attracts and precipitates negatively charged yeast cells.

If the beer is filtered prior to filling, it is best to place the beer in a cooled conditioning tank for a period of time before filtering to reduce particle counts and yeast counts. Make sure that the beer doesn’t come out with particles in the bottom of the tank. The less particles the beer contains before filtering, the longer the life of the filter and the higher the filtering efficiency.

In fact, polyphenolic proteins can be removed by precipitation at low temperature during winemaking. Cooling the beer to 0°C/32°F or lower prior to filtration will maximize the removal of cloudy particles, resulting in a clearer, more stable beer.