Diacetyl Control: Using ALDC to brew the beer you intended

What is ALDC? Alpha acetolactate decarboxylase.

Benefits of ALDC:

·        Reduces Diacetyl production
·        Significantly reduces maturation times
·        More efficient vessel utilisation
·        Improves beer quality

Diacetyl is well known among brewers and beer drinkers – distinctive for its buttery aroma and flavour. It is both produced and removed naturally by ale and lager yeast strains alike during the course of a typical fermentation and many reliable house yeasts leave a little residual diacetyl in the finished beer. As such it is fairly common with many traditional and popular beer styles to contain some level of diacetyl in their flavour profile.

Murphy and Son has worked with a number of craft breweries in the USA and United Kingdom who wanted to produce modern, hoppy pale ales without any flavour of diacetyl, but that was brewed using their existing house ale strain of yeast. The concentration of diacetyl was initially monitored to see how it was being lowered by the breweries controlled fermentation and how effective the yeasts own ability to reabsorb and reduce the diacetyl during maturation was.

Murphy and Son analysed this beer for diacetyl levels in their laboratory in Nottingham, England. It was found that by applying ALDC to the wort at the same time as the yeast was added in a concentration of 3 to 4 grams per hectolitre, the flavour would be brought below threshold in the finished beer as desired (figure 1).

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ALDC is commonly used in lager production to lower maturation time, the rate-limiting step, by converting acetolactate (the precursor of diacetyl) to a flavourless end-product called acetoin. (figure 2 below).

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In this instance the ALDC was able to boost the diacetyl lowering effect of the yeast in the same way, culminating in the desired low concentrations of diacetyl in the finished beer and allowing the brewer to broaden the spectrum of beers produced without the need for another yeast.

As ale fermentations are much faster a little more ALDC was required than may be needed for lager, but at 3 to 4 grams per hectolitre of ALDC it was still found to be an economical solution to the brewer.

Murphy and Son Ltd sell ALDC in 1kg pack sizes!

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