Development of Hydrogen Sulfide in Wine During Storage (Rachel Allison, PhD Candidate, Sacks Lab) & Novel, High-Throughput Methods for Trace-Level Analyses of Grape and Wine Volatiles using DART-MS (Jessie Rafson, PhD Candidate, Sacks Lab
From Rajni Aneja on May 12th, 2021
Rachel Allison, PhD Candidate, Sacks Lab, Cornell University
"Development of Hydrogen Sulfide in Wine During Storage”
Sulfur-like off-aromas (SLOs) are reportedly responsible for upwards of one quarter of the faults identified in premium wines in competition. Of the many volatile sulfur compounds (VSC) reported in wine, hydrogen sulfide (H2S, “rotten egg aroma”) is most frequently reported to be in excess of its sensory threshold (~ 1 µg/L) in wines with SLOs. H2S can be produced during fermentation through several pathways but is sufficiently volatile such that the majority formed during fermentation will be lost to CO2 entrainment. After fermentation, winemakers may attempt to remove H2S by inert gas sparging, or by aeration to oxidize H2S or other VSCs or by addition of cupric (Cu[II]) salts to form non-volatile complexes.
Jessie Rafson, PhD Candidate, Sacks Lab, Cornell University
“Novel, High-Throughput Methods for Trace-Level Analyses of Grape and Wine Volatiles using DART-MS”
There is a need for affordable, rapid, trace-level (sub-ppm) chemical technology to characterize large numbers of samples to proactively ensure high-quality and safe agricultural and food products. This is especially true for wine and grapes where large numbers of samples require analyses to assess smoke taint exposure, characterize breeding programs, etc. Solid-phase microextraction (SPME) is widely used in conjunction with gas chromatography-mass spectrometry (GC-MS) for volatile analyses in foodstuffs and other complex matrices. However, standard GC-MS quantitation methods generally require ~30-60 min per sample, making it suboptimal for high throughput analyses. Recent work from our lab has developed a method for the selective extraction and pre-concentration of volatiles which uses a planar sorbent sheet (SPMESH) headspace extraction prior to rapid analysis by Direct Analysis in Real Time (DART)-MS. Using this combined SPMESH-DART-MS approach, 24 samples could be extracted and analyzed in 45 min with detection limits of common odorants in the ng/L to µg/L range. While the original work using SPMESH-DART-MS was a substantial improvement over SPME-GC-MS, it still has its limitations. First, instead of being limited by a lengthy GC cycle, throughput is now limited by: (1) the equilibration time needed for a headspace extraction, (2) crosstalk within the system limiting the number of useable wells, and (3) the dimensions of the well plate itself. Additionally, the current range of compounds compatible with SPMESH-DART-MS is rather narrow. While SPMESH-DART-MS has previously worked well for non-polar, highly volatile compounds, it has poor performance with semi-polar volatiles and is incompatible with non-volatile compounds in headspace mode. This seminar presentation will discuss how we have overcome these challenges.