Impact of Pasteurisation on Terpenes, Terpenoids, Aldehydes and Esters in Hoppy Ales on Ageing

Pasteurisation is a common technique to achieve microbial stability of beer. In dry hopped beer, pasteurisation is the ultimate measure to assure product quality and consumer safety. To gain insights into the effects of pasteurisation on the chemistry of hoppy ales the time related changes of aldehydes, terpenes, terpenoids and esters in an unpasteurised and pasteurised session India Pale Ale (SIPA), two IPAs, and a double IPA (DIPA) were monitored. The ales were stored at 4 °C and 20 °C for 52 wk to evaluate chemical differences between the two treatments. It was found that pasteurisation led to an immediate increase of staling aldehydes (i.e., furfural and 2-methylpropanal), a decrease of fermentation esters (e.g. ethyl octanoate) and hop related esters (e.g. 2-methylbutyl isobutyrate) in fresh beer, while terpenes and terpenoids were hardly affected. When the beers were stored, unpasteurised ales were chemically less stable compared to the pasteurised ones. Differences between pasteurised and unpasteurised ales were dependent on storage temperature. The results of this study highlight that pasteurisation is favourable when aiming to achieve an increased shelf life of up to 12 months, as the negative influence of the heat impact is compensated after 1 month of storage at ambient (20 °C) temperature.