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Diacetyl free strains prevent diacetyl formation

As we saw in the previous section on How dry hopping can lead to diacetyl, when dry hop enzymes convert non-fermentable sugars to fermentable sugars, an ordinary yeast will convert fermentable sugars into α-acetolactate during a secondary fermentation (i.e. hop creep). This can be a problem for brewers, as they have to choose between either waiting days or weeks for the beer to pass a forced diacetyl test, or packaging and shipping fresh beer at the risk of diacetyl forming after it leaves the brewery.

Thanks to some smart bioengineering, brewers can combat diacetyl formation before it even starts. The way it works is by putting a gene that encodes ALDC into the yeast genome, the ALDC enzyme consumes α-acetolactate before it leaves the cell. That is, when dry hops are added to the fermentor, and the yeast begins a secondary fermentation, the ALDC enzyme consumes α-acetolactate as it is produced, so that diacetyl never rises above flavor threshold. As such, you can rest assured that your beer will stay so fresh and so clean.

Figure 1.