Rachel Allison, PhD Candidate, Sacks Lab, Cornell University
"Development of Hydrogen Sulfide in Wine During Storage”
Abstract
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”
Abstract
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.
Zoom Recording ID: 98225343013
UUID: icfw4SBVT2iMBlOFkS97bg==
Meeting Time: 2021-04-06T19:30:33Z