The Phenolic Composition of Hops (Humulus lupulus L.) Was Highly Influenced by Cultivar and Year and Little by Soil Liming or Foliar Spray Rich in Nutrients or Algae
The authors are grateful to the Foundation for Science and Technology (FCT, Portugal)
for financial support from national funds FCT/MCTES, to CIMO (UIDB/AGR/00690/2020) and
for Sandra Alonso’s doctoral scholarship (BD/116593/2016), and also for national funding by FCT,
P.I., through the institutional scientific employment program-contract for M. I. Dias and L. Barros
contracts. To the project “GreenHealth—Digital strategies in biological assets to improve wellbeing
and promote green health” (Norte-01-0145-FEDER-000042) funded by the European Regional
Development Fund (ERDF) under the scope of Regional Operational Program North 2020.
The interest in expanding the production of hops outside the traditional cultivation regions,
mainly motivated by the growth of the craft brewery business, justifies the intensification of studies
into its adaptation to local growing conditions. In this study, four field trials were undertaken on
a twenty-year-old hop garden, over periods of up to three years to assess the effect of important
agro-environmental variation factors on hop phenol and phenolic composition and to establish its
relationship with the elemental composition of hop cones. All the field trials were arranged as
factorial designs exploring the combined effect of: (1) plots of different vigour plants year; (2) plots
of different plant vigor algae- and nutrient-rich foliar sprays year; (3) plot liming year;
and (4) cultivars (Nugget, Cascade, Columbus) year. Total phenols in hops, were significantly
influenced by most of the experimental factors. Foliar spraying and liming were the factors that
least influenced the measured variables. The year had the greatest effect on the accumulation of
total phenols in hop cones in the different trials and may have contributed to interactions that often
occurred between the factors under study. The year average for total phenol concentrations in hop
cones ranged from 11.9 mg g1 to 21.2 mg g1. Significant differences in quantity and composition
of phenolic compounds in hop cones were also found between cultivars. The phenolic compounds
identified were mainly flavonols (quercetin and kaempferol glycosides) and phenolic carboxylic acids
(p-coumaric and caffeic acids).
