Evaluating the physiology and fermentation performance of the lager yeast during very high gravity brewing with increased temperature

Very high gravity brewing can achieve effective energy saving and significant emission reduction, and thereby has been progressively applied in beer industries. However, the yeast cells encountered multiple environmental stresses during very high gravity brewing, resulting in the sluggish fermentation. To overcome this issue, a practical strategy, that is increasing the fermentation temperature, has been used. However, to which extent the temperature could be increased and whether the higher temperature would influence the viability and vitality of the cells that would be re-used for the next run of fermentation remains unclear. In this study, we compare the fermentation performance of three lager yeast under different temperatures (11 degrees C, 15 degrees C, 18 degrees C). Yeast cell growth and fermentation rate analysis show that a higher temperature can indeed increase the fermentation rates. However, the taste value and volatile compounds analysis indicated that different temperatures have also changed the flavor fingerprint dramatically. Meanwhile, lower cell viability and flocculation ability could be caused by the higher temperature. Hence, increasing the fermentation temperature in a reasonable range is an available method for coping sluggish problem in very high gravity brewing.