As a potential novel technique in the wine-making industry, ultrasound has received considerable attention. In this paper, a model wine system was constructed to investigate the effect of ultrasonic irradiation on the formation of xanthylium cation pigment derived from the (+)-catechin and the glyoxylic acid, an oxidation product of tartaric acid, so as to explore the changing mechanism of the wine color mediated by ultrasound. The results indicate that the long-term ultrasonic treatment can enhance the formation of the xanthylium cation pigment in the model wine, which is attributed to free radicals triggered by ultrasound, meanwhile, iron ions and oxygen can influence the ultrasonic effect. All these results suggest that ultrasound is promising to be employed in regulating the formation of the yellow pigment during wine aging thus modifying the wine organoleptic characteristic.
Empty-cup aroma persistence (ECAP) is a key indicator of Baijiu quality, yet mechanisms underlying its modulation remain unclear. GC–MS analysis revealed that ECAP positively correlation with medium-/long-chain esters/aldehydes/acids and lactic acid (LA), while certain volatiles showed negative correlation, which possibly due to flavor interactions involved low-volatility like LA. QDA and E-nose detection confirmed that LA supplementation (5–25 g/L) prolonged ECAP by 25% in strong-aroma and 300% in soy-sauce-aroma Baijiu. In 52% ethanol-water model, 1 H NMR demonstrated LA (0.297–4.476 g/L) transformed ethanol hydrogen-bonding from chain-like ( δ 5.350 ppm) to tetrahedral ( δ 4.780 ppm) configurations. Downfield shifts (Δδ −0.091 to −0.111 for ethanol –OH; −0.46 to −0.50 for LA –CH) confirmed new hydrogen bonds. Partition coefficient (kg/m) and molecular dynamics simulations indicated that LA concentration-dependently suppressed ethanol (optimal: 0.595 g/L). These findings demonstrated that LA enhanced ECAP through hydrogen-bonding network restructuring, providing scientific basis for intelligent Baijiu blending.
In order to explore the effects of ultrasound on the formation of acetaldehyde and its mechanism in model wine solutions, ultrasound conditions and free radicals were investigated by response surface methodology and electron paramagnetic resonance spectroscopy (EPR), respectively. The results indicate that ultrasound does induce the production of acetaldehyde with the maximum amount under the conditions of ultrasound power density 0.2 W/cm 2 , 48 min and 32 °C. The hydroxyl radicals and the 1-hydroxyethyl free radicals are the main initiator and precursor for acetaldehyde, respectively. Furthermore, the stronger the 1-hydroxyethyl free radicals captured by EPR, the lower the formation of acetaldehyde. In addition, the content of Fe 2+ and ethanol also exerted a certain influence on the acetaldehyde formation. In conclusion, ultrasound does promote the production of acetaldehyde in the model wine solutions, which is beneficial for well understanding the mechanism of ultrasound in modifying the wine color and accelerating ageing.
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