Nonvolatile organic acids (NVOAs)
associated with the Laobaigan flavor type of Baijiu
were analyzed by a derivatization method,
and 37 NVOAs were quantified. In addition, 33 odorants were judged
to have high flavor dilution factors by application of aroma extract
dilution analysis and quantification by gas chromatography coupled
with mass spectrometry (GC–MS) and GC combined with quadrupole
time-of-flight MS. The quantitative data obtained for the odorants
and NVOAs were used to recombine the overall flavor of Baijiu. The
odor of the reconstitution of the odor-active volatiles and the NVOAs
was more similar to that of the original Baijiu sample than the sample
that only contained odor-active volatiles, and the alcoholic and sweety
flavor odor characters were reduced, while others, that is, fruity,
acidic, floral, jujube and grain, were amplified. It was shown for
the first time that NVOAs have effects on the volatiles in Baijiu
and might obviously influence the intensity of certain aroma qualities.
The
sensory impacts of two thiols, 2-methyl-3-furanthiol (MFT)
and 2-furfurylthiol (FFT), in Chinese soy sauce aroma-type Baijiu
(SSB), strong aroma-type Baijiu (STB), and light aroma-type Baijiu
(LTB) (liquor) were evaluated and combined with partial least squares
discriminant analysis (PLS-DA) to differentiate Chinese Baijiu. The
flavor dilution factors of these two thiols ranged from 81 to 6561,
and quantitative results showed that MFT and FFT were significantly
more abundant (p < 0.001) in SSB than in STB and
LTB. The determined odor activity values (OAVs) suggest that MFT (OAV:
34–121) and FFT (OAV: 11–103) contribute significantly
to the overall aroma profiles of LTB and STB. Interestingly, the OAVs
of these two thiols were high (256–263) and did not significantly
differ (p > 0.05) in SSB. Notably, hierarchical
cluster
analysis and PLS-DA results revealed that these compounds can be used
to differentiate Chinese LTB, STB, and SSB. According to their prominent
organoleptic and distinguishing roles, these two thiols can be regarded
as flavor markers for SSB.
By applying the aroma extract dilution analysis, 13 esters were found to have high FD factors in the Laobaigan flavor type of Baijiu. These were then quantified using GC-MS. In addition, 35 nonvolatile organic acids were quantified by a derivatization method combined with GC-MS. The perceptual interactions of lactic acid and ethyl lactate and that of lactic acid and ethyl acetate were studied through the olfactory threshold. The S curve was used to evaluate the changes in the olfactory thresholds. After adding lactic acid (1142, 20 000, and 53 703 mg/L), the olfactory thresholds of ethyl lactate (1000, 724, and 295 mg/L) and ethyl acetate (398, 324, and 257 mg/L) decreased obviously, which revealed that lactic acid gave additive or synergistic odor effects for the two esters. Furthermore, it was discovered that as the concentrations of lactic acid increased, the extent of the interaction among these compounds was also greater in the mixture.
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