Effects of Brewing Conditions on the Quality of Xanthoceras sorbifolium Leaf Green Tea Infusion

To investigate the effects of brewing conditions on the nutritional quality and flavor of Xanthoceras sorbifolium leaf green tea, tea infusions prepared with different combinations of brewing temperature and duration were analyzed for concentrations of nutrients such as total phenols, free amino acids, flavonoids, caffeine, and soluble sugars, taste and volatile components. The results showed that the nutritional quality and flavor of tea infusion both differed significantly under different brewing conditions, and the infusion state of active substances also varied. Infusion at 70 ℃ for 60 min led to the highest concentration of total phenols (0.66 mg/mL). The concentration of free amino acids peaked at 18.44 mg/mL after infusion at 80 ℃ for 360 min. The level of flavonoids reached a maximum value of 0.56 mg/mL after 180 min of infusion at 90 ℃, and the concentrations of caffeine (0.14 mg/mL) and soluble sugars (10.39 mg/mL) were the highest after 720 min. Comprehensive analysis using membership function showed that the tea infusions brewed at 80 ℃ for 360 min, 90 ℃ for 30 min, and 70 ℃ for 720 min received relatively high scores. Furthermore, electronic tongue analysis revealed that these infusion samples had similar overall taste profiles, with the sensor responses to umami, bitterness, and richness being the highest. Electronic nose results indicated that the W1W sensor exhibited the highest response to all three tea infusions. Using gas chromatography-ion mobility spectrometry (GC-IMS), we identified 66 volatile compounds in the tea infusions, from which 21 differential volatile compounds and 12 key volatile compounds were selected. Among these, 1-octen-3-one, 2-methylbutanal D, and n-octanol were the most important aroma components. This study provides guidance for the scientific consumption of X. sorbifolium leaf tea.