Brewing with syrups.

Pfisterer, E.A., Garrison, I.F. and McKee, R.A.

Abstract
Even in breweries with cereal cookers, the addition of syrup adjunct to the kettle is becoming more and more attractive since it provides sufficient increase in brewhouse capacity at a lower cost than a major expansion. Unfortunately, because of the high glucose content in these syrups, not all yeast strains may adapt equally well to the resultant change in the fermentable carbohydrate spectrum. Depending upon the malt/adjunct ratio, the glucose concentration can increase up to 300% in the syrup adjunct wort as compared to a control wort. A production ale yeast appeared to be sensitive to the elevated glucose levels in these worts and seemed to exhibit a repression of the maltose uptake system (catabolite repression); this resulted in 'hanging fermentations' with unacceptably high amounts of yeast fermentable extract in the beers at dropping. Although it was possible to end ferment the syrup adjunct worts by changing brewing and fermentation conditions, a more convenient alternative arose when a high maltose and low glucose syrup became available in Canada. By using a maltose releasing enzyme rather than glucoamylase after the acid conversion of starch, a distribution of fermentable carbohydrates is achieved in the syrup which almost matches the pattern found in the wort. The addition of the high maltose syrup to the kettle did not affect the fermentation performance of our ale yeast.
Keywords: adjunct beer brewers yeast brewing composition fermentation mashing syrup