The development and use of modified hop extracts in the art of brewing.

Todd, P.H., Held, R.W. and Guzinski, J.G.

Abstract
The history of the development of hop products containing chemically modified (rho, tetrahydro and hexahydro) iso alpha acids is outlined and the differences in molecular structure between normal iso alpha acids and their different chemically modified forms are briefly explained. The elucidation of the mechanism of off flavour formation in lightstruck beer led to the recognition of the fact that the chemically modified iso alpha acids are not affected by the reaction concerned. Beers bittered with hop products containing only chemically modified iso alpha acids can therefore be bottled in clear or light coloured glass without loss of flavour stability. The effects of the different chemically modified iso alpha acids on beer bitterness and foaming properties are discussed. As the non bitter hoppy flavour/aroma constituents, derived from the essential oil, are not present in chemically modified hop products to any significant extent, hop oil preparations have been developed for use in conjunction with modified bittering products. The potential applications of these products in the brewing industry are briefly described.
Keywords : beer bitterness chemistry flavour iso alpha acid isomerised hop extract lightstruck off flavour stability