Pre-isomerised hop products - potential and practical use An up-to-date overview
The classical means (and only means allowed by the Purity Law) of bittering beer is by addition of hops or conventional hop products (pellets, extracts) to boiling wort. Iso-alpha-acids arise during boiling, these are the main bittering substances in beer. Should iso-alpha-acids be formed not in boiling wort but external to the brewery, one speaks of pre-isomerised hop products.
Iso-alpha-acids are formed from alpha-acids contained in hops (Fig. 1). Since 1947 when this transformation was explained chemically by Rigby, there have been efforts to have the reaction proceed under optimised conditions. When isomerising alpha-acids during wort boiling, losses of about 50% arise.e. a more cost-effective utilisation of hops. These are also classed as pre-isomerised hop products.g.
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