Effect of "Late Harvest" of Hops (Humulus lupulus L.) on the Contents of Volatile Thiols in Furano Beauty, Furano Magical, and Cascade Varieties

In recent years, many hop varieties with unique aromas, so-called "flavor hops", have been bred and grown. Here, we investigated the effect of late-harvested hops using three flavor hop varieties; Furano Beauty, Furano Magical, and Cascade. The sample hops were harvested at different days after flowering (DAF): DAF 45 (normal harvest), DAF 65, DAF 75, and DAF 85. We measured the volatile thiols in sample cones. The results indicated that 4-methyl-4-sulfanylpentane-2-one contents showed almost no change or a slightly decrease with a delay in harvest, whereas 3-sulfanyl-4-methylpentan-1-ol (3S4MP) content in late-harvested samples increased several fold in comparison with normal-harvested samples. Additionally, 3S4MP contents in the beers brewed with DAF 65 samples were several times higher than those using DAF 45 ones. From these results, we propose a new method to control 3S4MP content in hop cones by changing its harvest date.

Evaluation of Variety, Maturity, and Farm on the Concentrations of Monoterpene Diglycosides and Hop Volatile/Nonvolatile Composition in Five Humulus lupulus Cultivars

Pentose-hexose monoterpene alcohol glycosides were isolated and semiquantitatively measured in dried Humulus lupulus cones using UHPLC-qTOF-MS/MS and HPLC fractionation followed by GC-MS. The samples evaluated included hop cones from five important dual-purpose cultivars (varieties) in the United States, from two locations (farms) per variety and from three distinct harvest time points (maturities) per location, as dictated by dry-matter (% w/w) at the time of harvest. Hop variety accounted for the biggest variation among the concentrations of pentose-hexose monoterpene alcohol glycosides as well as other volatile and nonvolatile chemical factors measured in the samples. This indicates that genetics plays a major role in hop flavor production. Interestingly, "maturity", or ripeness at the time of harvest, was the next most significant factor impacting the concentrations of pentose-hexose monoterpene alcohol glycosides along with most of the other volatile and nonvolatile factors (such as total oil concentration and composition). However, maturity notably had a bigger impact on some cultivars such as Sabro, Mosaic, Simcoe, and Citra. Surprisingly, farm (i.e., location, farming practices, etc.) accounted for the least amount of variation among the concentrations of the different analytical factors. These results highlight the importance of breeding/genetics as well as considering hop maturity/ripeness at the time of harvest on the production and subsequent development of analytical chemical factors associated with driving hoppy beer flavor. It is essential for future studies assessing the impact of different farming practices and locations (i.e., regionality, terroir, etc.) on the constituents in hops important for hoppy beer flavor to consider and account for the impact of hop maturity as well as genetics.