Factors affecting invertase activity during beer brewing, lagering and in the finished product
2007
Srogl, J.,Vyzkumny Ustav Pivovarsky a Sladarsky, Prague (Czech Republic) | Vernerova, H.,Plzensky Prazdroj, Plzen (Czech Republic) | Matasova, L.,Zapadoceska Univ., Plzen (Czech Republic). Katedra Chemie | Sigler, K.,Akademie Ved, Prague (Czech Republic). Mikrobiologicky Ustav
The article concerns the effect of temperature, yeast washing and different brewing technologies (classical process, cylindro-conical tanks (CCT) technology) on invertase activity during main fermentation, secondary fermentation and in finished beer. During secondary fermentation in the classical process at 1,0-4.5 deg C, as well as in the bright beer tanks, invertase activity (3.4-3.5 microkat/L) does not perceptibly change. It increases (up to 5.4 microkat/L) when the secondary fermentation proceeds at 22-24 deg C, with a concomitant increase in the level of free alpha-amino nitrogen as an indicator of cell lysis. As found in the CCT process, washed yeast releases into the finished unpasteurized beer less invertase than unwashed one and is thus obviously in a better physiological state. Beer produced with washed yeast was also evaluated as being sensorially superior. The amount of released invertase also increases with repeated yeast pitching. The activity of invertase in beer during secondary fermentation is constant throughout and the cells do not lyse during this process. When using CCT technology, the activity of invertase in filtered beer is similar to that found during the classical brewing process but exhibits a higher variability, obviously as a result of a less intensive blending of individual beer lots.
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