Quantitation of 4-Methyl-4-sulfanylpentan-2-one (4MSP) in Hops by a Stable Isotope Dilution Assay in Combination with GC×GC-TOFMS: Method Development and Application To Study the Influence of Variety, Provenance, Harvest Year, and Processing on 4MSP Concentrations

Abstract

A stable isotope dilution assay was developed for quantitation of 4-methyl-4-sulfanylpentan-2-one (4MSP) in hops. The approach included the use of 4-(C)methyl-4-sulfanyl(1,3,5-C)pentan-2-one as internal standard, selective isolation of hop thiols by mercurated agarose, and GC×GC-TOFMS analysis. Application of the method to 53 different hop samples revealed 4MSP concentrations between <1 and 114 μg/kg. Notably high concentrations were associated with United States varieties such as Citra, Eureka, Simcoe, and Apollo, whereas 4MSP was absent from traditional German and English varieties. Further experiments showed that besides the variety, also harvest year and storage vitally influenced 4MSP concentrations, whereas the impact of provenance was less pronounced. Hop processing such as drying and pelletizing had only a minor impact on 4MSP concentrations. Like the majority of other hop volatiles, 4MSP is predominantly located in the lupulin glands.

A chemometric approach to compare Portuguese native hops with worldwide commercial varieties

“…34,35 In addition, the particular composition of monoterpene alcohol, ester and sulphur-containing compounds has been reported as main contributor for the desired citrus and fruity flavours of American cultivars. [36][37][38][39] With the objective of understanding if the ROBPCA gathers specific information regarding hop samples and volatile compounds, the principal components scores were plotted (Figure 2). In the plots of group A, nine components were retained and accounted for 98.66% of the total variance.…”

Analysis of Potent Odour-Active Volatile Thiols in Foods and Beverages with a Focus on Wine

“…was preferred [25]. Apart from one-dimensional GC, two-dimensional separations of volatile thiols have also been explored with heart cut GC or GC×GC systems (Table 2, Entries 24, 27, 31) [23,27,57]. However, it was worth noting that, even with the enhanced resolving power of GC×GC, conventional sample preparation procedures without specific chemical derivatisation failed to detect a targeted thiol (4-MSP) due to the high background noise [27].…”

“…Even so, stable isotope labelled IS are the best option in a stable isotope dilution assay (SIDA), which is arguably the most accurate analytical approach, and, in most cases, can efficiently eliminate a matrix effect by compensating extraction, separation, and detection variabilities due to the almost identical properties between analytes and their stable isotope, labelled analogues [78]. SIDA has been widely employed for LC–MS [7,36,41] and GC–MS [19,25,27,30,31,32,33] methods for volatile thiols analysis, and both 2 H [7,19,25,30,32,33,36,41] and 13 C labelled [27] internal standards have been used in various cases (Table 2, Entries with bolded numbers). Typically, the ideal degree of atom labelling should be greater than two [76], but d 2 -3-SHA [36] and d 2 -3-SH [30,36] have been reported in a few cases as stable isotope labelled IS.…”

Studies on the odorant concentrations and their time dependencies during dry‐hopping of alcohol‐free beer

“…[1][2][3] For some hops, variety-specific odorants were identified like ethyl 2-methylbutanaote in Huell Melon or 4-mercapto-4-methylpentan-2-one in US varieties like Cascade, Citra, and Eureka. 4 Especially by late-or dry-hopping, higher concentrations of these hop odorants can be achieved in the final product. So that the transfer of hop odorants is not affected by evaporation during wort boiling, a more intense hoppy aroma can be achieved by hop addition into the whirlpool or in the cold area.…”

“…While, among others, 3-methyl-1-butanol, 2-phenylethanol, 2-methoxy-4-vinylphenol, and 2-and 3-methylbutanoic acid were identified as important key odorants in different beer types, 5,6 hop key odorants like linalool, geraniol, or 4-mercapto-4-methylpentan-2-one were shown as highly important for the typical aroma of dry-hopped beers. 4,[7][8][9] Also, different esters like ethyl 3-methylbutanoate and ethyl methylpropanoate were demonstrated to be present in concentrations above their odour thresholds in regular and alcohol-free dry-hopped beers. 7,10,11 In the past years, the market for alcohol-free beers strongly increased.…”