Impact of the Long-Term Maintenance Method of Brewer's Yeast on Fermentation Course, Yeast Vitality and Beer Characteristics

Abstract

The effect of the long-term maintenance method used with a brewer's yeast on its technological properties was determined in laboratory fermentation trials with a 12°P all-malt wort. The trials were performed at a constant temperature and under conditions of constant substrate concentration. Two cultures of a bottom fermenting yeast, Saccharomyces pastorianus RIBM 95, were tested -one culture was maintained by subculturing on wort agar slopes at 4°C and the other culture underwent a three year storage in liquid nitrogen at minus 196°C. Parameters under investigation included yeast vitality measured as acidification power (AP), fermentation time needed to reach an alcohol level of 4%, the yeast cell count, sedimentation of the yeast during the fermentation, and the production of beer flavour compounds in green beer. The yeast culture stored for three years in liquid nitrogen displayed a higher count of suspended cells, required a shorter time to attenuate the wort to produce 4% alcohol and produced a 1.5 to 2.5-fold higher concentration of a number of flavour compounds. The long-term storage method did not affect the sedimentation ability and vitality of the yeast strain tested.

Cryopreservation: The secret of modern preservation of brewer’s yeasts – minireview

“…In the brewing environment, it constitutes a widely employed technique mostly using a slant agar (e.g. malt agar) and a storage temperatures of up to 4 °C (Matoulková and Sigler, 2011). This method is simple and cheap, because specialised equipment is not required.…”

“…That is why this method is recommended primarily for collections with a small number of cultures which are used constantly and for short periods of time i.e. less than 1 year (Matoulková and Sigler, 2011).…”

“…Various liquified gases are used to reach this extremely low temperature, for example nitrogen, argon or xenon. Nevertheless, liquid or vapour phase nitrogen, with its working temperature range between -160 °C to -196 °C, is used almost exclusively due to safety and financial reasons (Matoulková and Sigler, 2011;Bond, 2007).…”

“…-160 °C), the cooling process is terminated. Finally, the frozen cryotubes are placed in racks and containers in a Dewar vessel and submersed in liquid nitrogen (Matoulková and Sigler, 2011).…”

Improvement of Ethanol Tolerance by Inactive Protoplast Fusion in Saccharomyces cerevisiae

“…Glutathione (GSH) is considered to be useful for detoxification and delaying senescence [39]. Meanwhile, moderate sedimentation ability should be proper for beer fermentation [40]. erefore, CO 2 weight loss, SO 2 content, α-N assimilability, GSH content, and sedimentation were used for the comparison of fermentation properties between Q/L fusants and their parents.…”