13,591
edits
Changes
→Temperature and Aromatic and Sensory Compounds
====Temperature and Aromatic and Sensory Compounds====
Just as with other strains of ''Saccharomyces cerevisiae'' used in fermentation, the fermentation temperature can have a significant effect on the different aromatic and flavor compounds produced by kveik [https://nmbu.brage.unit.no/nmbu-xmlui/handle/11250/2681970?show=full Aasen's Master's thesis] looked at fermenting three different full culture kveiks, Gamlegrua, Gausemel and Ørjasæter, and US-05 as a control. She tested three different fermentation temperatures, 22°C, 30°C, and 37°C. In general, after 7 days of incubation time, all of the yeasts had higher levels of the esters ethyl acetate, isoamyl acetate,and ethyl hexanoate at the 22°C or 30°C, and nearly half the amounts of esters at 37°C. These were esters were also measured at day 2, and at that time they were much higher in the 37°C fermentation, suggesting that prolonged exposure to the warmer temperature may have dissipated these esters. Ethyl octanoate tended to have slightly higher amounts at 22°C or 30°C, but the differences between the different fermentation temperatures were smaller, and in the case of the Gausemel kveik there was no significant different at all for this ester <ref name="Aasen" />.
It has been anecdotally reported by brewers that high levels of off-flavors from higher alcohols are not produced at fermentation temperatures up to 35-40°C with kveik. In general, Aasen's Master's thesis reflected these anecdotal reports. The amount of the higher alcohol 2-methyl-1-propanol was nearly double at 30°C and 37°C versus 22°C for the control yeast strain, US-05. For the three kveik cultures that were tested, Gamlegrua, Gausemel, and Ørjasæter, the amount of this higher alcohol was only slightly elevated at the higher fermentation temperatures, but still remained under the lowest levels that US-05 produced when fermented at 22°C. The higher alcohol 1-propanol had a similar trend. At 30°C and 37°C, US-05 produced significantly more of this higher alcohol, while the three kveik cultures produced only slightly elevated or the same levels regardless of fermentation temperature. The levels of 1-propanol that were produced by the three kveik cultures at all three fermentation temperatures were, in general, around the same amount that US-05 produced at 22°C. Two other higher alcohols that were measured, 2-methyl-1-butanol and 3-methyl-1-butanol, were roughly the same for all three fermentation temperatures for all three of the kveik cultures and US-05, with 2-methyl-1-butanol tending to be slightly higher in the warmer fermentation temperatures for all of the kveik cultures and US-05. One of the higher alcohols tested, 2-hexanol, had nearly double or triple the levels when fermented at the cooler temperature of 22°C versus 30°C and 37°C, indicating that this particular higher alcohol follows an opposite trend than most higher alcohols produced by yeast. The levels were the same for all three of the kveik cultures and US-05 <ref name="Aasen" />.
====Other Sensory Data====