Today in 1967, US Patent 3298835 A was issued, an invention of Murray Peter John Andrew, Clarke Brian James, Hildebrand Robert Peter, and Harold Frank Vincent, and assigned to Carlton & United Breweries, for their “Process for Production of a Hop Concentrate.” Essentially it’s a “process for the production of a hop concentrate wherein the flavour imparting constituents of hops are increased by extracting and then converting inactive constituents to active flavour imparting constituents.” There’s no Abstract, but this is from the description:

The process of this invention involves the utilization of those constituents which are regarded as relatively inactive or which do not normally impart the desired flavour characteristics to brewed beverages and which are not converted to any substantial degree to active flavour-imparting constituents during treatment by existing. processes. In the process of our co-pending application the relatively inactive hop constituents of a-acids known as humulones are converted to the more active iso-humulones by the process of isomerization. It is an object of the present invention to provide an improved process for the production of a hop concentrate for brewing purposes, whereby the lupulones content of the p-acids of hops may be utilized in addition to the humulone content of the a-acids, thereby increasing the flavouring or bittering characteristics of the hop concentrate final product for the production of a brewed beverage.