In the brewing industry it is very important to take care of several parameters such as flavor, aromas, color, CO2, pH, turbidity, among others to maintain the quality and be within the taste of consumers, in this case we will talk about turbidity an important parameter to take care of the development. The turbidity is formed by particles in suspension, which reflect light. Among these particles, highlight the yeast cells, proteins and tannins (polyphenols), which are the main culprits of the problems of clarity. To measure the turbidity we only need a turbidity meter, that is, a special device that measures the intensity of light reflected in the particles of a beer sample, at a 90 degree angle and, in general, according to the color scale EBC. Even the highest quality meters have their limitations, mainly due to the “false turbidity” (pseudo-haze in English), a turbidity that the meter can detect perfectly, but that is not perceptible to the human eye. This phenomenon, then, happens when the small particles do reflect the light, but they do not affect the clarity of the finished beer. From this premise, one could also say that turbidity describes the visible particles, while lapseudo-haze measures the difference between the turbidity detected by the meter and that which the human being can appreciate. Although this may seem foolish, the truth is that the false turbidity is quite an affront to the commercial breweries, determined to control the stability and turbidity of their products.
The main causes of turbidity
Any brewer who wants to exercise an exhaustive control of the clarity of his beer must inevitably look at proteins and polyphenols, mainly from malt and hops. Also, a secondary concern is the yeast in suspension, which also contributes to turbidity, especially when it comes to young beers.
Although there are other reasons why a beer can be cloudy (musts with calcium deficiency, dead bacteria, yeast in poor condition, etc.), the main responsible for the turbidity are proteins, polyphenols and yeast.
Problems of clarity in beer derived from yeast
Yeast cells are much larger than polyphenols (between 0.005 and 0.01 mm), so they can directly cause problems of clarity, especially when it comes to young beers. The majority of yeast particles, at the end of fermentation, flocculate and precipitate towards the bottom of the fermentor, thus creating a kind of sediment. However, there are always some diluted cells in the beer. These could cause turbidity weeks or even months later, even when the beer has already been bottled or boiled.
One of the ways to greatly reduce the turbidity generated by yeast is to choose the correct culture of brewer’s yeast. Depending on the strain, the flocculation ratio is different. In this way, the yeasts with a high flocculation, as the name says, will flocculate quickly and will originate more crystalline beers. In contrast, strains with low flocculation will trigger attenuated and cloudy beers.
However, if we have used a low flocculation strain and later we want to eliminate the yeast, there are some techniques or substances that can help us. Also the cold, to a large extent, promotes the flocculation of the yeast. For this reason, many breweries age and / or store their products at a temperature around 0ºC.
Finally, some processes can be executed to eliminate yeast, such as filtration or pasteurization. Here the debate is open, because these practices (especially pasteurization) are directly related to the production of industrial beer, and are badly seen in the craft beer sector.
Therefore it is necessary to have online measurement to ensure the quality and clarity of the beer according to its type.