The influence of storage conditions on the chemistry and flavor of hoppy ales.

Understanding the factors which lead to the (in)stability of the chemistry and sensory of hoppy beer styles such as India Pale Ales (IPAs) has become a major concern for many brewers. Therefore, the evolution of several volatiles under different storage conditions (room temperature, cold storage, forced aging) was investigated in eleven hoppy ales and one lager which were commercially produced in Germany. Compared to the lager, the fresh ales contained higher initial aldehyde levels. Furthermore, the distribution of lipid oxidation and Maillard reaction products differed from those typically found in lager beer. Upon storage, significant increases of some staling aldehydes were observed. Interestingly, the concentrations of some hop aroma volatiles like terpenoids (i.e. linalool and geraniol) were relatively stable throughout storage and counteracted "oxidized" impressions in ales high in these compounds. In comparison, hop aroma in some ales was driven by less stable volatiles such as esters.

How deviations in the elemental profile of Humulus lupulus grown throughout the U.S. and Germany influence hop and beer quality.

Recently studies based on limited sample sizes procured from minor hop growing regions have speculated that the elemental profile of hops can possibly be used to authenticate the origin of a hop because changes in hop elemental profiles were realted to growing region and that these changes might also be related to beer quality. To explore this further, 205 hop samples (i.e. 203 whole cone hops and 2 pelletized samples) compromised of 19 varieties were procured from the major hop growing regions (i.e. the U.S. and Germany). These hops were digested with microwave digestion and analyzed for 25 elements using ICP-MS. Hops from most of the U.S. regions (mainly WA) had vastly different elemental profiles than hops from Germany. German hops had significantly lower concentrations for most of the elements except for Cu and K. Interestingly, high alpha varieties had significantly different elemental profiles than varieties bred for aroma purposes. Dry-hopping trials were then performed in an ale and a lager with the hops that had significantly different elemental profiles. Although heavy metals were extracted from hops into beer, at the 5 g/L dry-hopping load used in this study, beer concentrations of these elements remained below regulated water quality standards set by Germany, the U.S., and Canada. Based on electron paramagnetic resonance, dry-hopping had an antioxidant impact on beer regardless of the original elemental profile of the hops which was correlated to hop polyphenol and α/ ß - acid concentrations. Overall these results highlight that many factors including location have the potential to influence the elemental profile of hops and that changes in the elemental profiles of hops can be related to beer quality.

Analysis of Hop-Derived Thiols in Beer Using On-Fiber Derivatization in Combination with HS-SPME and GC-MS/MS.

The quantitation of the hop varietal thiols 4-mercapto-4-methyl-2-pentanone (4MMP), 3-mercapto-1-hexanol (3MH), and 3-mercaptohexylacetate (3MHA) from beer is challenging. This primarily relates to their low concentration (ng/L levels) and their reactivity. Published assays for thiol quantitation from beer include complex and/or time-consuming sample preparation procedures involving manual handling and use reagents that are harmful because they contain mercury. To facilitate thiol analysis from beer, the current article is concerned with the implementation of an automated headspace solid-phase microextraction (HS-SPME) on-fiber derivatization (OFD) approach using 2,3,4,5,6-pentafluorobenzyl bromide followed by gas chromatography-tandem mass spectrometry (GC-MS/MS). Optimization of HS-SPME and MRM conditions was based on a central composite design approach. The final OFD-HS-SPME-GC-MS/MS method yielded limits of quantitation below the sensory thresholds of 4MMP, 3MH, and 3MHA. Method validation and application on beers brewed with German, Australian, and US hops, as well as with added fruits displayed excellent method performance.