Fate of Resveratrol and Piceid through Different Hop Processings and Storage Times

Abstract

trans-Piceid and trans-resveratrol contents of hop cones, hop pellets, CO₂ extracts, and spent hop from American varieties (harvest 2004) were determined by reverse-phase high-performance liquid chromatography−atmospheric pressure chemical ionization−tandem mass spectrometry [RP-HPLC−APCI(+)−MS/MS]. Pelletization induced strong stilbene degradation in some cultivars. Similarly, 1 year of storage at 4 °C led to a huge loss of trans-piceid, especially in the case of hop cones (much faster than in model media, although well protected from light and oxygen). Therefore, after 8 months of storage, the overall stilbene content was in the same range whatever the conditioned form. Absent in fresh hop cones or pellets, cis-resveratrol was released from cis-piceid in all stored samples. On the other hand, no δ-viniferin was detected despite it is present in light-protected model media spiked with trans-piceid. Because supercritical carbon dioxide proved inefficient for recovering resveratrol and piceid from pellets, spent hop emerged as the most interesting material for subsequent specific stilbene extraction.