Breakdown of hop bitter substances during storage of beer
Bitter acids do not remain stable in beer. They break down, depending on time, temperature and incident light. Enquiries from breweries provided grounds for investigating the decrease in 25 commercial beers once again. Within a month of filling, the beers were subjected to ageing for eight months at 22 °C while protected from light. The only differentiation related to hopping according to the indication on the label. These beers were hopped either with pellets, extract or both products.
Together with bitterness units in accordance with Analytica-EBC 9.8, the a-acids and iso-a-acids were measured using HPLC (EBC-Proceedings Maastricht 1997, page 223-231).
Table 1 gives the absolute measured values.2% relative for iso-a-acids and 13.8% relative for bitterness units.
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