Pitching Rate in High Gravity Brewing

The changes in the proton efflux rate (PER) during fermentation of normal gravity (NG), high gravity (HG) and very high gravity (VHG) wort by a lager yeast (Saccharomyces pastorianus) were monitored using an optimized PER test method. The values of the proton efflux rate in S. pastorianus decreased with increasing initial wort gravity. Moreover, the difference in the proton efflux rate values at the beginning of the fermentation was lower than at the end of fermentation from normal gravity to very high gravity brewing. These results demonstrated that the proton efflux rate in S. pastorianus was inhibited in the later stages of high gravity and very high gravity brewing. Furthermore, the changes of the proton efflux rate in S. pastorianus under the high ethanol concentration conditions appeared to depend on the concentration of ethanol in the fermentation liquid. A better negative correlation (P < 0.001, r = -0.95) between the ethanol concentration at >4% (w/v) and the proton efflux rate was found. The changes of the proton efflux rate in the cells treated with exogenous ethanol confirmed that higher concentrations of ethanol could significantly inhibit proton efflux in S. pastorianus. This study offers a possible way to monitor and explain the performance of yeast in the complex environment of high gravity and very high gravity brewing.

Section: Wort Preparation and Fermentationmentioning

confidence: 97%

The Dynamic Changes of Proton Efflux Rate in Saccharomyces pastorianus Strains During High Gravity or Very High Gravity Brewing

Zhang

Zhao

Wan

et al. 2011

“…The slowest fermentation rate was with spontaneous fermentation without inoculation. Several workers 12,17,20,32 have stated that increasing the inoculum level resulted in a faster fermentation rate with brewer's and wine yeast strains.…”

Section: Effect Of Inoculum Level On the Course Of Fermentationmentioning

confidence: 99%

“…Although there are various studies on the effects of pitching levels of brewer's yeasts on beer fermentation 12,30,32 , information concerning the effects of the pitching level of the wine yeast S. cerevisiae on wine fermentation is scarce. Mateo et al 20 found that inoculum levels affected wine fermentation and volatiles.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Inoculum Level on Fermentation and Flavour Compounds of White Wines Made from cv. Emir

Erten

Tangüler

Cabaroğlu

et al. 2006

In this study, the influence of the addition of a commercial wine yeast (Saccharomyces cerevisiae) at inocula of 1 × 104 to 1 × 107 cells/ml in Emir must was investigated with a focus on yeast growth, fermentation rate, ethyl alcohol and flavour compound formation. Spontaneous fermentation without inoculation was also performed. Higher peak counts were observed with higher amounts of S. cerevisiae yeast. Addition of various amounts of yeast led to the earlier disappearance of non‐Saccharomyces yeasts. The fermentation rate was improved with higher amounts of yeast, but ethanol production was not affected. Concentrations of higher alcohols increased with increasing inoculum levels, especially inoculum sizes of 1 × 106 cells/ml and 1 × 107 cells/ml. The amount of ethyl acetate was reduced with increased inoculum levels.

“…An ideal brewing yeast should exhibit constant flocculation characteristics during consecutive rounds of fermenting, cropping, storing and repitching. Improved and reproducible flocculation is currently important because many breweries are using increasingly high-gravity worts, which are believed to be associated with sub-optimal yeast sedimentation 92 . The present review targets practical aspects of yeast flocculation that are relevant to brewer's yeast strains under industrial brewery conditions.…”

Section: Introductionmentioning

confidence: 99%

125th Anniversary Review: Yeast Flocculation and Sedimentation in Brewing

Vidgren

Londesborough

2011

Flocculation is prerequisite for bulk sedimentation of yeast during brewery fermentation. Although single yeast cells gradually sediment in green beer, this sedimentation rate is too slow without formation of large yeast flocs. The present review concerns the major determinants of yeast flocculation and sedimentation in brewery fermentations. Flocculation characteristics of yeast are strongly strain-dependent and largely defined by which FLO genes are functional in each strain. In addition to the genetic background, several environmental factors affect flocculation. These can be, somewhat arbitrarily, classified as physiological factors, such as the calcium availability, pH, temperature and ethanol and oxygen concentrations in the medium or physical factors, such as cell surface hydrophobicity, cell surface charge and the presence of appropriate hydrodynamic conditions for the formation of large flocs. Once yeast flocs are formed, their size, shape and density and the properties of the surrounding medium affect the rate at which the flocs sediment. Higher gravity worts usually result in green beers with higher viscosity and density, which both retard sedimentation. Moreover, environmental factors during yeast handling before fermentation, e.g., propagation, storage and cropping, influence the flocculation potential of yeast in subsequent fermentation. Premature yeast flocculation (PYF) and the role of PYF factors are discussed. In conclusion, some potential options available to adjust yeast flocculation are described.