Pre-extraction treatment of various aroma and bitter hops by pulsed electric fields results in an increased bitterness, but an almost constant aroma composition

Abstract

The effect of pulsed electric field (PEF) treatment strongly depends on specific product properties, e.g. the phenotype of the processed plant species. However, for food products it is crucial that quality parameters are maintained and that processing is reproducible. In the present study, PEF treatment was used for improving the extraction of hop compounds for beer production. Considering the fact that the flavor and aroma of a beer develops during the boiling process and is highly dependent on the hops used, PEF was applied as a pre-extraction procedure treating concentrated hop suspensions to improve the extractability of aroma compounds. A total of eight aroma and bitter hops were studied to consider putative variety-specific effects of PEF. Investigations of the bitterness and flavor (sensorial/instrumental) also showed putative and hop-dependent influences of the PEF treatment: Significant increases in the bittering units of between 48% (cv. ‘Polaris’) and 285% (cv. ‘Huell Melon’) were observed in three concentrated and PEF-treated hop extracts. A change of olfactory attributes was not perceived. Similarly, SPME-GC-MS was only able to determine negligible changes in 21 volatile aroma compounds, including four off-flavors. However, some larger increases in heptanoic and octanoic acid were observed in the PEF-treated cultivar ‘Huell Melon.’ The findings of the present study indicate that PEF can be successfully applied as a pre-extraction technique for treating hop components, suggesting its potential use in breweries for increasing the bittering units without negatively influencing the overall flavor, or for lowering costs by reducing the required quantities of expensive hops.