This study examined the effects of different concentrations (5, 25, and 45 mg/kg) and types (siloxane F695, silicone F3011, and organosilicon emulsion F1520) of defoamers on the defoaming, physicochemical properties and sensory evaluation of ‘Rougui’ oolong tea beverage. The optimal timing of addition and concentration for each defoamer were determined. Subsequently, headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) was employed to analyze the effects of the three defoamers at their optimal concentrations on the flavor of tea beverage. The results showed that adding F695 or F1520 at low concentrations (5 mg/kg) before foam formation exhibited the best anti-foaming effect. The defoamers showed no significant effect on the key physicochemical parameters of tea beverage. Addition of excess defoamers to the tea beverage increased its turbidity and astringency and caused off-odors, thereby deteriorating sensory quality. Subsequent experiments showed that low-concentration defoamers exerted significant impacts on the aroma components of the tea beverage. A total of 112 aroma components were identified. Through orthogonal partial least squares-discriminant analysis (OPLS-DA) and the Kruskal-Wallis H test, 28 key differential aroma substances were identified. Relative odor activity value (ROAV) analysis indicated that the three defoamers significantly inhibited the release of most volatile substances. Among them, F1520 exhibited the least impact on aroma substance contents, causing no significant changes in the total ROAV of key aroma substances (fruity, honey-like, and fresh notes) compared with the control group. In conclusion, 5 mg/kg of organosilicon emulsion F1520 is suitable for application in ‘Rougui’ oolong tea beverage. It eliminates foam that has already formed and also prevents the formation of new foam, while largely retaining the tea beverage’s flavor characteristics. This study reveals how defoamers affect the flavor of tea beverage, providing a theoretical basis for quality control and flavor optimization in tea beverage production.

This study employed sensory evaluation, electronic nose and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) to evaluate the efficacy of different concentrations of silicone-based anti-foaming agent in Rougui oolong tea beverage and evaluate their effects on the flavor and aroma characteristics of the beverage. The results demonstrated that the low and medium concnentrations of anti-foaming agent effectively reduced the foam height and shortened the collapse time, with the effect being more pronounced upon the addition of the anti-foaming agent before than after foam generation. The addition of excess anti-foaming agent caused the tea infusion to become turbid and increased the astringency and off-flavors, leading to quality deterioration. Significant differences in sensor responses among the different treatment groups were observed for E-nose sensors W5S (nitrogen oxides), W1S (short-chain alkanes), W1W (inorganic sulfides), and W2W (aromatic components and organic sulfides). Different concentratons of anti-foaming agent had a significant effect on the aroma components of the beverage. A total of 110 aroma compounds were identified, and 26 key differential compounds were selected by orthogonal partial least squares-discriminant analysis (OPLS-DA) and Kruskal-Wallis H test. Relative odor activity value (ROAV) analysis revealed that the contents of aroma components such as linalool, dihydrolinalool, phenylethyl alcohol, and trans-nerolidol remarkably declined with increasing concentration of anti-foaming agent, and the release of these aroma components was inhibited by the anti-foaming agent, possibly altering the overall aroma profile. Based on the anti-foaming efficacy and sensory balance, the optimal anti-foaming agent concentration was determined as 0.005–0.025 g/kg, effectively controlling foaming while preserving the flavor well. This study helps elucidate the mechanism by which antifoaming agents influence tea beverage aroma, providing theoretical insights for quality control and aroma optimization in tea beverage production.