Control of natural conditioning in beer.

Carroll, T.C.N. and Wenn, R.V.

Abstract
When a beer is naturally conditioned the exact amount of fermentable sugar present at the beginning of the conditioning period is extremely important in determining the amount of carbon dioxide which will be produced. Guinness stout is normally primed with a repitched wort and so the assessment of fermentable sugar is particularly difficult. The traditional method involved measurement of the specific gravity of the beer after primary fermentation and also after fermentation to the attenuation limit. An hplc technique has now been applied to measure the residual fermentable sugars in the bulk beer as well as in the fresh gyle. Unfortunately, the separation procedure is such that some non-fermentable sugars such as isomaltose and cellobiose could be included with fermentable sugars and so produce an overestimate of fermentability. This problem has been overcome not by improving the resolution of the hplc but by making an allowance for the non-fermentable 'background' sugars. The concentration of these compounds was determined by applying the hplc technique to a fully attenuated beer. The new method has proved to be very satisfactory in a test involving approximately 80 beer samples. 87% of the samples were found to be within 0.4o using the new and the traditional method.
Keywords: beer conditioning fermentability fermentation HPLC