Conditioning, Clarification, Stabilization
Clarification
At the completion of fermentation, the beer contains some yeast, colloidal particles of protein–polyphenol complexes, and other insoluble material that was driven out of solution by the low pH and the cold temperature during aging. If a brilliant, clear beer is desired, the clarification must remove these substances before beer packaging can be done. Four basic clarification techniques are used either separately or in combination: (1) sedimentation, (2) use of fining agents, (3) centrifugation, and (4) filtration, which is discussed in more detail in Chapter 15, Beer Filtration. Sedimentation and the use of fining agents can be employed during the conditioning phase.
Gravity Sedimentation
Gravity sedimentation is the simplest method for achieving clarity by chilling of fermented beer to about 0 degrees C (32°F) for long periods of time. However, despite its simplicity, caution is needed because yeast autolysis occurs readily, especially if the packed yeast mass begins to heat. With clarification by sedimentation, beer losses are relatively large and clean-up of tank bottoms is costly.
Fining Agents
Isinglass
Although good clarity can be obtained from simple sedimentation, better results can be obtained in less time by using fining agents such as isinglass. Isinglass has a positive charge at beer pH, which is attracted to negatively charged yeast cells, allowing them to form large particles that can be removed by sedimentation. Usually, isinglass is used to precipitate yeast from top-fermenting beer. Its effectiveness in settling ale yeast varies with the strain of yeast, and it is generally not recommended for precipitating lager yeast.
Influence of pH. Fining performance is pH dependent, with some isinglass types producing superior performance at lower beer pH values, while other types favor beers of higher pH. There appears to be a pH threshold, of approximately 3.4, below which fining activity is severely inhibited.
Yeast Count. Many brewers believe maintaining yeast counts within a reasonable range (0.5–3.0 x 106 cells/mL will provide satisfactory fining performance without the need to adjust fining regimes (Ward, 2020).
Level of Particulate Matter. An excess of positively charged colloidal material in the beer, such as positively charged calcium ions, may reduce the fining action of isinglass by reducing the charge on the yeast cell (Ryder et al.,2006).
Effect of Temperature. It is recommended that isinglass be added to the entire run of beer after primary fermentation and at the time of cooling or during transfer (Thompson, 1984). Beers should be dosed at their coldest temperature in the entire supply chain, which is most likely to be in the brewery at some point after the end of fermentation and before packaging.
Preparation. Preparation of isinglass is dependent on the physical form used as starting material. If the isinglass is in its raw form, it needs to be “cut” using acids. There is some evidence that organic acids provide a better product than inorganic, with tartaric acid being the most preferable acid (Ryder et al.,2006).
Dosage Rate. The optimum dosing rate is determined by adding isinglass at different rates to beer samples. As the isinglass dose rate increases, so does the clarity of the beer, until the optimum fining dosage rate is reached. This is the point that gives the brightest beer in the least time, with the minimum generation of bottoms.
Auxiliary Finings
The negatively charged auxiliary finings come in two main types—acidified silicates and acidified polysaccharides. The negative charge enables the auxiliary finings to react with positively charged proteins. The silicates are strong protein reactants and have a significant fining action of their own in beer. Indeed, silicate auxiliaries can be used to reduce yeast and/or fine particle levels in beers where the level is too high to allow normal fining. Auxiliary finings are often used in conjunction with isinglass finings for improved clarity (Leather, 1994).
Dosing Procedures for Fining Agents
The optimal method of adding finings is to proportionally inject it at a point of high turbulence, preferably against the direction of the beer flow. Dosing all of the finings into part of the beer, and then adding the rest of the beer on top will result in under fining one portion of the beer, and over fining the other portion, resulting in poor clarity, and excessive volumes of bottoms.
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