Humulus lupulus L. cv. Cascade grown in Northern Italy: morphological and phytochemical characterization.

Several aroma hops (Humulus lupulus L.) were recently introduced in Northern Italy as a small-scale production of excellence. In this preliminary study, the American cv. Cascade, was investigated in a combined morphological and phytochemical survey. Morphological investigation on trichome structure, density and distribution by scanning electron microscope (SEM) and light microscope was performed. Essential oil composition, α/β-acid and polyphenol profiles over three years were determined by GC-MS and HPLC analyses. Two types of non-glandular (simple and cystolithic) and glandular (peltate and bulbous) trichomes were observed on leaves and female inflorescences (cones). The peltates resulted as the main sites of terpene production and accumulation. The essential oil profiles showed myrcene, β-caryophyllene, (E)-β-farnesene and humulene epoxide II as the dominant compounds over the three collection times, although with diverse relative abundances. The presence of two exclusive compounds, γ-muurolene and trans-γ-cadinene, characterized the investigated samples, potentially enhancing some typical organoleptic traits of the Cascade hop cultivated in Northern Italy, such as the herbal, woody and spicy aroma descriptors. For what concerns bitter acid composition, the quantitative values resulted consistent to literature data only at the second and third monitoring year. Qualitative differences in polyphenol content were also recorded, with particular reference to the presence of quercetin-3-O-malonylglucoside and kaempferol-3-O-rutinoside, which may characterize this peculiar Italian cultivation.