Production of novel varietal hop aromas by supercritical fluid extraction of hop pellets—Part 2: Preparation of single variety floral, citrus, and spicy hop oil essences by density programmed supercritical fluid extraction

Abstract

In this study on the production of novel varietal hop aromas by supercritical fluid extraction of hop pellets we aim at fractionated extraction of hop oil essences by density programmed supercritical fluid extraction (SFE) of hop pellets T90 using carbon dioxide. For that purpose, SFE is performed in two steps. In the first step, the most volatile compounds from hop essential oil are isolated by extracting pellets T90 applying a carbon dioxide density of 0.29g/mL (90atm, 50°C). Subsequent fractionation of the crude extract from this first SFE step via solid phase extraction (SPE) using octadecylsilica and ethanol/water mixtures, results in flavour-active single variety hop oil essence, highly enriched in ‘floral’ compounds of total hop essential oil. When added to a non-aromatised pilot lager, such varietal essences impart pleasant and pronounced floral, hoppy and citrus scents to the beer flavour. In the second step of the SFE procedure, the hop residue from the first extraction step is further extracted using a carbon dioxide density of 0.50g/mL (110atm, 50°C). As a result of the typical construction of the collection vials and further fractionation of the crude SFE extract via SPE, single variety hop oil essence, highly enriched in oxygenated sesquiterpenoids (‘spicy’ compounds), is obtained. When added in appropriate amounts to a non-aromatised pilot lager, such ‘spicy’ essences impart revealing sensory impressions, i.e. pleasant herbal/hoppy aroma, and in particular, increased bitterness intensity, mouthfeel, and fullness.