Effect of harvest time on some in vitro functional properties of hop polyphenols.

Health benefits of hop polyphenols are well studied. In the present investigation, we examined the antioxidant activity, anti-nitric oxide (NO) production, and anti-adipocyte differentiation of polyphenols extracted from hops (HPP), harvested at different times for over 4years. Saaz hop variety from the Czech Republic was used in the in vitro assays. Twenty-three polyphenols were quantitatively analyzed using Orbitrap liquid chromatography-mass spectrometry (LC-MS), and their health promoting effects were assayed individually. Strong effects of low concentrations of HPP were observed in the above three assays. A significant increase in anti-adipocyte differentiation activity per unit weight of HPP was obtained in the early harvested samples. A significant difference in anti-NO production activity per unit weight of HPP was observed among the different harvest years. HPP significantly increased in early harvested samples. Our results suggest that some in vitro functional properties of hops vary with harvest time and year and are dependent on different polyphenols.

The influence of pruning and harvest timing on hop aroma, cone appearance, and yield.

Humulus lupulus (hop) cone is a key ingredient of beer, which determines its taste and aroma. Thus, it is necessary to control its cultivation conditions to acquire suitable quality. Here, cultivation conditions, such as pruning, blooming, and harvest timings, were modified for the Saaz hop variety in the Saaz region of Czech Republic. We investigated the correlation between the abovementioned cultivation factors and hop aroma characteristics, chemical components, appearance, yield, and beer quality in four locations and in three years. Harvest timing had a significant impact on the amount of essential oils, especially monoterpenes. Among them, linalool, geraniol and myrcene, which contribute beer hoppy aroma, increased with delay in harvest timing. These impacts caused by harvest timing were confirmed in all 4 locations and in all 3years. Our findings suggest that harvest timing influences the intensity and quality of beer hoppy aroma.