Changes in Brewer's Yeast during Storage and the Effect of These Changes on Subsequent Fermentation Performance

Abstract

A slurry of brewer's yeast in beer was stored in two, 200-bbl cylindroconical vessels at 1.6° C. One was maintained full, while 34% of the yeast was removed from the other vessel after 24 hr. The yeast was stored in both vessels for a total of 80 hr. Samples were removed at intervals and analyzed for glycogen, trehalose, and viability. Aliquots of each yeast sample were pitched into 2 L of wort. Yeast glycogen and trehalose declined only slightly in the full vessel, but in the other vessel, glycogen declined significantly after removal of a portion of the yeast. Viability of the yeast stored by either method remained between 90 and 96%. Fermentations of the yeast stored by either method showed no relationship between yeast fermentation performance and glycogen or trehalose content. The fermentation performance of yeast stored under these industrial conditions was independent of glycogen or trehalose content and several reasons for this are discussed.

Storage of Pitching Yeast in Brewery

“…During the storage its vitality is affected mainly by temperature (McCaig and Bendiak, 1985b; O'Connor-Cox, 1998a; Somani et al, 2012), the starvation period (Martens et al, 1986), oxidative stress (Boulton, 1991; Maemura et al, 2007;McCaig and Bendiak, 1985a;Skladování násadních kvasnic v pivovaru al., 1998;McCaig a Bendiak, 1985a;Sall et al, 1988), mícháním (McCaig a Bendiak, 1985a). Uvedené stresové faktory nepůsobí odděleně -jejich účinky se kumulují (Gibson et al, 2007).…”

“…Obsah glykogenu přesahuje 40 % sušiny buňky a je ovlivňován podmínkami kvašení a skladování a také závisí na vlastním kmenu kvasinek (O'Connor-Cox et al, 1996). Jako zdroj energie je glykogen využíván při biosyntese lipidů, sterolů a vyšších mastných kyselin, zejména v lag fázi v následující fermentaci (Bolat, 2008;Sall et al, 1988). K akumulaci glykogenu v buňkách dochází ve střední až pozdní fázi kvašení.…”

“…Cílem tohoto kroku je rychlé ochlazení kvasnic na teplotu, při které se metabolismus zpomalí na minimum. Nejvhodnější systém pro rychlé chlazení je in-line chladič, kterým jsou kvasnice ochlazeny na teplotu 2-4 °C Sall et al, 1988), and by stirring (McCaig and Bendiak, 1985a). These stress factors do not affect the yeast separately -their effects are cumulated (Gibson et al, 2007).…”

“…Glycogen content exceeds 40% of cell dry weight and it is affected by the fermentation and storage conditions and also depends on the yeast strain (O'Connor-Cox et al, 1996). Glycogen is used as the source of energy for the biosynthesis of lipids, sterols and higher fatty acids, especially during the lag phase in the following fermentation (Bolat, 2008;Sall et al, 1988). Glycogen accumulation in cells occurs in the middle to late fermentation phase.…”

Disc Stack Centrifuge Operating Parameters and Their Impact on Yeast Physiology

“…The use of yeast cell glycogen content as a sensitive parameter to evaluate physiological status and fermentation performance has been well documented by many brewing scientists 1,11,24,25,30,37 . Glycogen serves as a reserve carbohydrate and promotes the synthesis of lipids during aerobic conditions, stimulating cell membrane structural integrity 25 .…”