Brewer's Corner - March 2010

We’re almost there. After successful wort boiling, the assimilation of various aspects of hop character and hot break removal we are ready for the final steps before primary fermentation. The wort in the whirlpool is still very hot. It is much too hot to pump to the fermenter for fear of killing our all important yeast. In order to protect our precious wort from contamination it is vital for a rapid chilling en route to the fermenter to secure vigorous yeast fermentation as quickly as possible. This is critical to the microbial stability of the beer. Enter the heat exchanger.

In line between the whirlpool and the fermentation vessel we have a heat exchanger in place. It works much like the radiator in your car but instead of using air as a cooling media we use chilled water. The heat exchanger consists of a series of heat exchange plates. These plates separate the wort path from the chilled water path. Hot wort enters on one side of the plate as the chilled water courses through the other. An exchange of heat occurs between the hot wort and the 5 degree Celsius water. Hot water is evacuated from the chiller and collected to the hot liquor tank for later use. What was once hot wort has now been chilled to the desired fermentation temperature.

Besides the necessary cooling to ensure we do not poach our yeast another miracle of brewing occurs at this time. The rapid chilling of the wort also precipitates what’s called cold break. This is basically the continuation of what we began in the wort boil as hot break. The cooler temperatures enhance the further precipitation of protein and protein- polyphenols. Lack of cold break can enhance ester production by the yeast as well as the formation of fusel alcohols. The presence of fusel alcohols are always a defect and are characterized by a solvent- like heat or alcohol taste in the finished beer. This is not to be confused with the alcohol taste from a strong beer. The key phrase “solvent- like” is critical to understanding and tasting this. A strong ester profile may or may not be a defect depending upon the style of beer being brewed. As the beer enters the fermenter the cold break settles and can be removed after primary fermentation. Some amount of cold break in the wort is considered important to enhance cell growth due to the presence of sterols, a vital element in the production of cell walls.

One last element to wort chilling is the injection of oxygen into the wort stream. Oxygen is important at only this step and its dissolution should be avoided at all other points in the brewing process. The yeast as it moves through its fermentation stages begins with aerobic fermentation. At this point the yeast metabolizes the O2. Oxygenation levels going to the fermenter may influence cell growth by providing fatty acids for sterol production which is as mentioned, important for cell wall growth. Ester and phenol formation are also greatly influenced by oxygenation levels.

There you have it dear readers, the final steps up to when the little fungi take over and render our wort to that most delicious of beverages. Beer… guaranteed to conquer any thirst and assure that for a brief moment, we are all bullet- proof.

Joe Schiraldi

VP Brewing Operations