Wort Concentration Research Articles

EVALUATION OF FERMENTATION PARAMETERS DURING HIGH-GRAVITY BEER PRODUCTION

A large number of advantages are obtained from the use of highly concentrated worts during the production of beer in a process referred to as "high-gravity". However, problems related to slow or stuck fermentations, which cause the lower productivity and possibility of contamination, are encountered. This study examines the influence of factors pH, percentage of corn syrup, initial wort concentration and fermentation temperature on the fermentation parameters, namely productivity, wort attenuation and the yield coefficient for sugar-to-ethanol conversion. The results show that productivity increased when the higher temperature, the higher wort concentration and the lower syrup percentage were used, while wort attenuation increased when lower wort concentration and no syrup were used. The yield coefficient for sugar-to-ethanol conversion was not influenced by any of the factors studied.

Changes in the yeast metabolism at very high-gravity wort fermentation.

The rate of ethanol production increased with increasing wort gravity up to the initial wort concentration of 24%, reaching the maximum ethanol concentration of 6.2%, but its attenuation reached only 49%. The intracellular trehalose accumulation was proportional to the initial wort gravity, at 24 or 30% wort fermentation increased 3 or 4.5 times, respectively, compared to 12% wort fermentation. Trehalose accumulation began after exhaustion of glucose, ceased after uptake of approximately 65% reducing saccharides, despite of increasing ethanol or remaining saccharide concentration in the environment.

High-gravity brewing utilizing factorial design

A number of factors can influence the behavior of yeast during fermentation. Some of these factors (initial wort concentration, initial pH and percentage of corn syrup in the composition of the wort) were studied in order to determine their influence on the productivity of fermentation. Fermentations were carried out at 25oC utilizing a 23 factorial design of these factors. The results showed that the percentage of corn syrup had no influence on process productivity, whereas initial pH and especially initial wort concentration did. It can be concluded that using pH and initial wort concentration values higher than those utilized in this work (5.5 and 20oP, respectively) will result in a higher productivity.

Removal of Volatiles from Very-High-Gravity Beer Fermentations by Gas (CO2) Stripping

The use of periodic forced gas (CO2) stripping of ethanol and fusel oils from active very-high-gravity (1.080) beer fermentations has been shown to be a possible technique for both keeping ethanol levels low and manipulating the overall volatile balance of the beverage. Volatiles carried over in the gas stream were recovered by condensation (−8°C) and their extraction was shown to be related to medium concentration, gas flow rate, and fermentation temperature. The rate at which ethanol, isobutanol, isoamyl alcohol, and propanol were removed reflected their condensate-stripped wort concentration ratio and was linked to their respective volatiles. A rise in fermentation temperature from 17 to 22°C increased the volume stripping rate by over 100% and the relative quantity of ethanol removed by 30%. At the same fermentation temperature, raising the gas flow rate four times resulted in a threefold rise in the total volume extracted, but the ethanol concentration ratios remained similar.