Type of Resources
In the brewing industry, there are four main ingredients that are required to produce beer: water, yeast, barley, and hops. Hops are used in many different stages of brewing. The key reason for their use is the conversion of humulone (a-acids) during the boiling process to cis- and trans-iso-humulone (iso-a-acid). These compounds are the main contributors to the bitterness in beer. Humulone undergoes an acyloin condensation to form a 5-membered ring. Magnesium ion concentration and the pH of the solution are important mediators of this reaction. We envisioned exploration of this mechanism using UV-vis spectroscopy and polarimetry to determine the binding constant of metals to the humulone. The results, coupled with computational analysis, indicated that Mg2+ binds to the anion of humulone resulting in structural changes that promote the rearrangement.