Proper control of the various steps to make a quality beer
By Michael Trommer
In order to keep the high standard of the beer, physicochemical control is essential. Various items in the beer production must be controlled:
– accurate analysis of primitive extract, apparent extract, alcohol content, degree of fermentation (complete fermentation), pH value, among others;
– determination of diacetyl content, bitterness value, dissolved oxygen, and colloidal stability, via forcing tests and other analyses.
It is known that the apparent measurement of the beer extract is not correct, because the alcohol present in the product can alter the final result.
In order to obtain the real measurement of the original extract (or primitive extract), the alcohol must be removed via distillation. This evaporated volume is then replaced with water before measuring the extract. This determination can be performed through refraction or distillation.
In this method, the beer color is assessed subjectively by using a spectrophotometer, rather than with the naked eye.
The pH value influences the stages of enzymatic decomposition in the wort and determines protein solubility and wort color during boil.
Beers with high pH are always beers in which few nitrogen compounds coagulated, were precipitated, and got removed from the medium through wort boil. For that reason, their protein stability is usually reduced. The optimum pH value is 5.2 to 5.6 during mashing and 4.0 to 4.3 in the finished beer.
Determination of oxygen in the beer
It is a great challenge to avoid air/oxygen pickup in the stages of filtration and filling of the finished beer. There are many methods to measure the oxygen.
In efficient filling systems, it is possible to obtain 0.10 mg O2/l. Most beer filling systems have an air pickup value of 0.5 mg O2/l.
Determination of diacetyl content in the beer
In most breweries, diacetyl is controlled in the fermentation stage. The cold phase must only be started when the diacetyl content reaches 0.10 mg/kg. The lower the value, the better. Nowadays, this control is performed in a gas chromatograph most of the time.
Determination of foam stability
The most important criterion is foam stability (head retention). The most used method for that analysis is the NIBEM.
Determination of bitterness (IBU)
Determining the bitterness of the beer is an important parameter. It is performed using a spectrophotometer.
The concentration of carbon dioxide content dissolved in the beer is also an important item of quality control:
- Low fermentation beers: the concentration must be between 0.40 and 0.60%;
- High fermentation beers: the concentration must be between 0.40 and 1.00%.
Determination of turbidity
Another very important analysis is the determination of turbidity. Certain methods are capable of providing results (about whether or not the beer will become turbid in a short period of time) in only a few days. The most important method is the forcing test, which goes as follows:
There are alternative methods, but the principle is always the same.
Biological control of the process
It is possible to find foreign microorganisms along the wort and beer path until obtaining the finished beer.
When these microorganisms propagate in the beer, they leave a fine sediment on the bottom, before making the beer cloudy. After that, the metabolic process of the foreign microorganisms affects the taste of the beer, making it unpleasant or undrinkable.
Not all microorganisms that somehow propagate in the wort or beer are harmful. It is possible to determine the health risk level as follows:
1- Microorganism flora that is non-harmful to the beer and humans;
2- Microorganism flora that is potentially harmful to the beer and humans;
3- Microorganism flora that is necessarily harmful to the beer.
A non-harmful flora consists of mold spores and many bacteria and yeasts. They cannot propagate in the beer.
A potentially harmful flora can only propagate in the beer if the latter presents appropriate characteristics for such contamination, such as:
Those bacteria are:
Some of those bacteria, such as Lactobacillus lactis, produce lactic acid. Pectinatus cerevisiiphilus and Megasphaera cerevisiae develop a strong smell of sewage.
The necessarily harmful flora propagates in oxygen-free beers with a low pH level. Over time, it also propagates in the bottled beer.
This group includes the following bacteria:
Microbiological control of the process
The role of microbiological control is to collect and analyze previously established points of the process to determine in which of them the wort and the beer are being contaminated.
It is important to take samples only from significant points. A data collection plan must be devised.
With special focus on maintaining sterility, the samples must be collected and then placed on Petri dishes containing nutrients for propagation of the microorganisms. In an incubator, the dishes with the sample material are maintained at 37°C – at this temperature, the contaminant spores propagate and form visible cells colonies. Under a microscope, the type of contaminant can be recognized from the colony formation.
Out of every batch of beer, one sample (transparent bottle) is taken and placed in a stability chamber at 26°C. This sample must not present sediment nor turbidity during the shelf life of this batch.
Microbiological control is of utmost importance in detecting any contamination before it can affect the shelf life of the product.
With these physico-chemical analyses, it is possible to achieve constancy of product quality. In order to provide this quality in all senses, it is ideal to perform microbiological control and standardize the entire process.
Automation is a very strong ally, which, along with standardization, prevents flaws in the process that may affect the finished beer.
In order to ensure constant quality, it is necessary to work using preventive and predictive maintenance.
By applying these points in the brewing process, we can raise a toast to a product with guaranteed quality.
KUNZE, Wolfgang. Technologie Brauer und Mälzer. Berlin, Germany: VLB.
ANGER, H.-M.. Brautechnische Analysenmethoden. Freising, Germany: Self-published by MEBAK.