Enzymes for Brewers (V: Kinetics II, Temperature)


A graph of the Arrhenius equation (not to be confused with an Arrhenius plot).

This is another installment in the Enzymes for Brewers series. 

The rate of an enzymatic reaction increases with temperature. This is because the molecules in solution are traveling at a higher speed, lowering the average time it takes for them to collide. Back in 1889, the Dutch chemist Svante Arrhenius derived a simple equation that showed the effect of temperature on the rate of any chemical reaction. Basically, his equation predicts that the rate of any chemical reaction will increase exponentially with temperature. Experiments have shown that his equation is remarkably accurate for a wide range of chemical reactions.

In chemistry, a rough rule of thumb is that, for every 10 °C increase in temperature, the rate of a reaction doubles. This is only an approximation, and the exact rate of increase depends on a rate constant specific to each reaction. (A rate constant is just a number that describes how fast the reaction proceeds. It has to be measured for each specific reaction.) However, for a surprisingly wide number of “simple” chemical reactions, this rule of thumb is “close enough” for most practical purposes. If the reaction is actually a net reaction of a series of chemical reactions, or a cascading reaction, this approximation can be way off.

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What Measurements to Record on Brewday: I


Whether on paper or on a computer or tablet, a brewing notebook is a repository of your accumulated brewing knowledge.

Learning how to brew better beer involves learning not only the abstract concepts, but the practical details of how things work in your brewery. One of the best ways to find out how your system works and have a repository of this information is to keep a brewing notebook. A brewing notebook is not just a place to store all your recipes — if you take detailed notes on your brewdays, it will contain a wealth of information. This information will allow you to check on information from prior beers. In addition, and perhaps more importantly, it can help you plan your future brew days and make future brewdays run more smoothly. In general, there should be a point to every measurement you record. On the other hand, measuring and recording various things during your brewday doesn’t take long and may be useful later. Here are some of the things you can record in your brewing notebook and how they can help you.

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