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Aspects of internal recycling of recoverable yeast beer
Schneeberger, M., Back, W., Krottenthaler, M.

The influence of blending fresh and aged yeast beers to pitching wort and to green beer on various parameters of the final beer is demonstrated within this study. Most of these parameters are not or only slightly influenced by the addition of yeast beers, but especially sensory attributes like foam and flavour were negatively affected by higher blending ratios of aged yeast beer. Also a discrepancy between measurable and sensory perceived flavour stability was observed. Within this aspect, 2-furfural plays a key role as the formation of this compound is repressed in yeast beers. Further studies are necessary to clarify this aspect. In order to recover high quality yeast beer it is recommended to avoid long storage periods of surplus yeast suspensions, especially at high temperatures, before processing and to flash pasteurize the recovered yeast beers to inactivate yeast enzymes. Blending ratios of 5% v/v to pitching wort or to green beer should not be exceeded.

Descriptors: surplus yeast, yeast beer, recovery, separation, flavour stability, foam stability

BrewingScience - Monatsschrift fr Brauwissenschaft, 59 (September/October 2006), pp. 148-162