Oxidized alpha acids are how much less bitter compared to iso-alpha acids?

Oxidized alpha acids, which are the products formed when alpha acids are subjected to oxidation, exhibit a significantly reduced bitterness when compared to iso-alpha acids, which are the primary compounds responsible for the bitterness in beer. When alpha acids are heated or oxidized, their bitterness can diminish significantly, leading to a perception of reduced bitterness in the finished product.

While iso-alpha acids contribute a strong bitterness, oxidized alpha acids can be approximately 66% less bitter, meaning that when they undergo oxidation, the bitterness they impart is substantially reduced. This reduction in perceived bitterness is relevant in brewing, especially when considering the impact of storage conditions, handling, and the age of hops, as it can affect the overall flavor profile of beer.

The other options reflect different percentages of bitterness reduction, but the understanding of the drastic decrease in bitterness caused by the oxidation process aligns with the accepted knowledge in brewing science, thus making the selection of 66% accurate.