By Grady Hull Assistant Brewmaster New Belgium Brewing Company, Fort Collins, CO USA Olive Oil Addition to Yeast as an Alternative to Wort Aeration MBAA-Rocky Mountain District Meeting September 15, 2007

Yeast requires oxygen to synthesize the fatty acids needed for cell membrane health But…. In the presence of oxygen these same fatty acids and other compounds can be oxidized to form stale flavors Brewing Dilemma

We do everything we can to prevent even the slightest amount oxygen ingress throughout the process But…. We saturate the wort with either air or pure oxygen at the start of fermentation

How much damage does this dissolved oxygen do? Factors that influence reaction times: Yeast takes up oxygen very quickly so reaction time is short The D.O. concentration is high; often close to saturation The reaction temperature is moderate; typically between 8 and 24 degrees C. Turbulence is obviously very high during knockout

Alternative Solutions Yeast Aeration Risk of glycogen and trehalose exhaustion due to increased metabolic activity Different yeast strains react differently so the amount of oxygen, contact time and success in general dependent on strain Increased yeast handling equipment required

Alternative Solutions Addition of Unsaturated Fatty Acids –Successful laboratory trials have been conducted using linoleic acid –Yeast has been shown to take the UFA’s up into the spheroplasts during cold storage –Yeast remains in dormant phase so glycogen stores remain

Why did we choose full scale testing with olive oil? The lower cost and availability of olive oil make it more practical for production than linoleic Oleic acid is the same 18 carbon monounsaturated fatty acid naturally produced by yeast Full scale testing necessary to give a true picture of cellar performance

The Questions We Were Trying to Answer Is it possible to achieve a normal fermentation, with normal flavor attributes using olive oil as an alternative to wort aeration? Will the resulting beer have a significantly improved resistance to oxidative staling?

Full Scale Test Procedure Four batches of Fat Tire were made using olive oil addition to yeast as an alternative to wort aeration. The batch sizes were 360 hl, 720 hl, 2100 hl and 2100 hl. The last 2 batches were bottled and sold without blending –Roughly 1.4 million bottles of Fat Tire were brewed and sold without wort aeration

Amount of Olive Oil Needed The amount of olive oil needed was increased over the four trials –In the 360 hl batch the olive oil was added to the yeast at a rate of 1 mg / 67 billion cells pitched –In the 720 hl trial the concentration was increased to 1 mg / 50 billion cells –In the 2100 hl trials the concentration was increased again to 1 mg / 25 billion cells

Trial One Results

Trial Two Results

Trial Three Results

Trial Four Results

Results Normal production wort fermentations can be carried out using yeast treated with olive oil instead of wort aeration This procedural change effected ester and fusel oil production, fermentation speed, and overall flavor perception Attenuation, pH, and foam were not affected.

Results Ester production was increased in all tests, although this increase was not deemed to be out of specification for the brand by the flavor profile analysis panel. The rate of attenuation in all trials was slower than the control samples but the fermentations were complete and all final gravities were similar to controls.

In the last round of testing the olive oil test batch was judged by the panel to be significantly less oxidized than the control after a period of warm storage. This method of treating the yeast with olive oil during storage instead of aerating the wort did improve the overall flavor stability of the beer without compromising flavor quality. Results

Suggestions for Future Work Continue with the addition of olive oil to storage yeast but to experiment more with addition amounts and contact time Other types of unsaturated fatty acids such as linoleic acid could be used in place of olive oil.

Suggestions for Future Work Fermentation parameters such as temperature and pressure could also be manipulated to compensate for differences in fermentation. The addition of olive oil during yeast storage, combined with wort aeration, could be used to test improvements in fermentation performance.

Thank-you for your kind attention