Supercritical CO2 extraction of Chilean hop (Humulus lupulus) ecotypes

Abstract

Hops (Humulus lupulus L) have very stringent requirements of diurnal light hours during flowering. Thus, the beer industry is permanently assessing new agricultural land to grow hops, southern Chile being an excellent candidate for their introduction. Supercritical carbon dioxide extraction procedures were implemented to assess Chilean hop ecotypes. Based on results of a preliminary study with commercial samples (cv Nugget), 200 bar and 40°C were selected as extraction conditions. Very limited increases in extraction rate were observed when applying pressures > 200 bar; such pressures did not speed up the extraction of α-acids (bitter flavor principles), but rather increased the co-extraction of undesirable compounds (hard resins and chlorophyll pigments). On the other hand, the effects of retrograde condensation phenomena were just starting to subside at 200 bar, and thermal damage of samples could increase at >40°C. Ground cone samples of five local hop ecotypes, originating from Osorno, La Junta, Coyhaique and Elizalde Lake, were subsequently tested. Osorno exhibited a higher yield (65 g kg -1 oleoresin/substrate) than other Chilean ecotypes. Moreover, Osorno extract had a light yellowish color, as well as a higher content of bitter flavors (157 g kg-1 α-acid/extract) and 1.5-7.1 times more representative aroma compounds than extracts of the other ecotypes. However, all these indicators were very low compared with the commercial Nugget sample (134 g kg-1 oleoresin/substrate, 383 g kg-1 α-acid/extract, 14 times more aroma compounds than Osorno ecotype). © 2003 Society of Chemical Industry.