Net effect of wort osmotic pressure on fermentation course, yeast vitality, beer flavor, and haze

Abstract

The net effect of increased wort osmolarity on fermentation time, bottom yeast vitality and sedimentation, beer flavor compounds, and haze was determined in fermentations with 12 degrees all-malt wort supplemented with sorbitol to reach osmolarity equal to 16 degrees and 20 degrees. Three pitchings were performed in 12 degrees/12 degrees/12 degrees, 16 degrees/16 degrees/12 degrees, and 20 degrees/20 degrees/12 degrees worts. Fermentations in 16 degrees and 20 degrees worts decreased yeast vitality measured as acidification power (AP) by a maximum of 10%, lowered yeast proliferation, and increased fermentation time. Repitching aggravated these effects. The 3rd "back to normal" pitching into 12 degrees wort restored the yeast AP and reproductive abilities while the extended fermentation time remained. Yeast sedimentation in 16 degrees and 20 degrees worts was delayed but increased about two times at fermentation end relative to that in 12 degrees wort. Third "back-to-normal" pitching abolished the delay in sedimentation and reduced its extent, which became nearly equal in all variants. Beer brewed at increased osmolarity was characterized by increased levels of diacetyl and pentanedione and lower levels of dimethylsulfide and acetaldehyde. Esters and higher alcohols displayed small variations irrespective of wort osmolarity or repitching. Increased wort osmolarity had no appreciable effect on the haze of green beer and accelerated beer clarification during maturation. In all variants, chill haze increased with repitching.

Very high gravity (VHG) ethanolic brewing and fermentation: a research update

“…The beer brewed at increased wort osmolarity contained increased levels of diacetyl and pentanedione and lower levels of dimethyl sulWde and acetaldehyde. Esters and higher alcohols displayed small variations irrespective of wort osmolarity or repitching [64].…”

Stress responses in brewing yeast.

“…HGB or VHG (very high gravity) wort osmolarity is 1500-1800 mOsm/l, which may induce hyperosmotic stress that affects cell structures (vacuole, plasma membrane, cell wall), lowers yeast proliferation rate (lower suspended yeast counts), delays yeast sedimentation, and extends fermentation time by 15-90 % depending on yeast generation. In our experiments [52], beer brewed at increased wort osmolarity (16 o and 20 o ) had higher levels of diacetyl and pentanedione and lower levels of dimethylsulfide and acetaldehyde than beer brewed from normal 12 o wort. Esters and higher alcohols displayed small variations irrespective of wort osmolarity or repitching.…”

“…Při použití technologie HGB nebo VHG jsou kvasinky vystaveny osmolaritě 1500-1800 mOsm/l, která může indukovat hyperosmotický stres ovlivňující buněčné struktury (vakuolu, plazmatickou membránu, buněčnou stěnu), zpožďuje sedimentaci kvasinek a prodlužuje čas fermentace o 15-90 %, v závislosti na generaci kvasinek. V našich experimentech vykazovalo pivo připravené z mladin s vyšší osmolaritou (odpovídající 16 % a 20 % mladinám) vyšší hladiny diacetylu a pentandionu a nižší koncentrace dimethylsulfidu a acetaldehydu nežli pivo připravené z 12 % mladiny [52]. Odchylky v koncentraci esterů a vyšších alkoholů nesouvisely s osmolaritou mladiny nebo s počtem nasazení kvasinek.…”

The evaluation of production yeast strains from the Collection of the RIBM for HGB Technology.

“…Změnám metabolismu kvasinek při kvašení HGB mladin se věnuje kolektiv J. Pát-kové [5]. K. Sigler et al popisují čistý vliv osmotického tlaku mladiny na průběh fermentace, vitalitu kvasinek a aroma a zákal piva [6]. Vlivem vysokokoncentrovaných mladin na schopnost fermentace, produkci ethanolu a výživu kvasinek se ve své práci zabývá G. P. Casey et al [7].…”

“…For example Patricia L. Pratt et al described the influence of stress caused by osmotic pressure and ethanol on yeast viability and morphology [1].The scientific team of J. Patkova dealt with the metabolic changes in yeasts during the fermentation of high gravity worts [5]. K. Sigler et al described the single influence of osmotic pressure in the wort on fermentation process, yeast viability, flavour and beer turbidity [6]. The influence of high gravity wort on fermentation ability, ethanol production and yeast nutrition was studied by G. P. Casey et al [7].…”