13,591
edits
Changes
Hops
,added data from Kishimoto et al. (2021)
Other compounds have been associated with the oxidation of beta acids and are extracted during wort boiling. These are described as giving a long-lasting, lingering bitterness on the palate. They include hydroxytricyclo-lupulone, dehydrotricyklolupulone, and hydroperoxytricyklolupulone <ref>[http://www.sciencedirect.com/science/article/pii/S0308814609001770 Structure determination and sensory evaluation of novel bitter compounds formed from β-acids of hop (Humulus lupulus L.) upon wort boiling. Gesa Haseleu, Daniel Intelmann, Thomas Hofmann. 2009.]</ref>.
====IBU====
The overall effect of oxidized compounds in aged hops has been shown by Val Peacock, a former scientist at Anheuser-Busch. Peacock stored hops at four different temperatures for 18 months. His data showed that although the alpha acid content in the hops and the iso-alpha acid content in the beers brewed with them decreased the older the hops were stored, the measured IBU of the different beers was about the same. This is because the oxidized acids in hops show up in the same spectrum as iso-alpha acids when using the ASBC method of measuring IBUs with a spectrophotometer <ref name="Aron">[https://www.homebrewersassociation.org/how-to-brew/resources/conference-seminars Dr. Patricia Aron. "Bitterness and the IBU: What’s It All About?" HomebrewCon 2017 Presentation. ~34 mins in. Retrieved 09/05/2017.]</ref>. This data is shown below. Caleb Buck's experiment [[Hops#Aged_Hops_in_Lambic|seen below]] supports this. Although it has not been shown that oxidized alpha and/or beta acids can inhibit lactic acid bacteria, if they do, then this might help explain reports <ref>[https://homebrewingfun.blogspot.com/2019/11/one-gallon-spontaneous-fermentation.html Adam Kielich. "One Gallon Spontaneous Fermentation Beer Batch 5 Recipe and Brewday". Brain Sparging on Brewing. 11/16/2019.]</ref> of using aged hops that originally had a high alpha acid content retaining a strong inhibitory effect towards lactic acid bacteria.
| 70°F || 0.41% || 2.9 ppm || 11.0
|}
Kishimoto et al. (2021) reported similar results when making beers with forcibly aged hops. They aged Magnum hop pellets (14% AA) at 40°C and exposed to air for 3 days, 5 days, 7 days, 10 days 14 days, 21 days, 30 days, and 90 days. The hops aged for 14 days had 9.8% AA, 21 days had 4.4% AA, 30 days had 1.2% AA, and 90 days had 0% AA. The IBU (measured with a spectraphotometer using Method Beer-23A from the American Society of Brewing Chemists) for the different beers made with the aged hops was more or less the same despite how much alpha acids were left in the aged hops. However, beers brewed with the different aged hops reflected a rapid decrease in iso-alpha acids in the beers made with the aged hops. Percieved bitterness also decreased for the beers made with the aged hops, but not as much as the decrease in ppm of iso-alpha acids, again demonstrating the oxidized hop compounds carry some bitterness, but less bitterness than iso-alpha acids <ref name="Kishimoto_2021" />.
See also: