Influence of steeping conditions on the green tea infusion quality from Xanthoceras sorbifolium bud

Xanthoceras sorbifolium Bunge, belonging to the Sapindaceae family, has been one of the most potential promising woody oil species in northern China. X. sorbifolium can play the important ecological roles, including desert greening, windbreak, and sand fixation, also providing for the edible and medicinal value among plant resources. Furthermore, X. sorbifolia can be used as nature food for health protection and disease prophylaxis in recent years, such as for tea, due to its high concentration of unsaturated fatty acids, especially neuroprotective nervonic acid. The leaves and buds of X. sorbifolium also share the nourishing ingredients and bioactive substances, including amino acids, proteins, soluble sugars, polyphenols, flavonoids, and saponins. In this study, a full-factor design was adopted with five levels of steeping temperature and seven levels of steeping time. Nutritional quality of the tea infusions was evaluated under 35 combinations. A systematic investigation was conducted to fully clarify the influence of brewing conditions on the quality of the tea infusions with the Xanthoceras sorbifolium bud green tea (XBT). Fuzzy A fuzzy membership function was used to screen the optimal brewing parameters. The aroma and taste of the tea infusions with XBT were characterized by gas chromatography-ion mobility spectrometry, electronic nose, and electronic tongue. The results showed that the content of tea polyphenols in the tea infusions of XBT first increased, then decreased, and finally tended to be stable, with the extension of steeping time. While the contents of total free amino acids, flavonoids, and caffeine generally showed a trend of first increasing and then decreasing. At the same time, a higher brewing temperature was conducive to the dissolution of soluble sugar components. Fuzzy The fuzzy membership function also showed that the long-term brewing (360, 720 min) was not conducive to the overall quality of the tea infusions, while short brewing time (5 min) together with low temperature (50, 60 ℃) failed to fully dissolve the nutrients in the tea infusions of XBT. Three optimal combinations of steeping parameters were obtained: 70 ℃ for 60 min, 90 ℃ for 30 min, and 80 ℃ for 30 min. A total of 60 volatile organic compounds and 13 key aroma substances were detected in the tea infusions. 2-methylbutyraldehyde and 3-methylbutyraldehyde jointly contributed to the roast aroma of tea infusions, while both octanal and hexanal contributed to the fresh fruit aroma of the tea infusions, and pentanal contributed to the grassy aroma of the tea infusions. The brewing conditions of 70 ℃ for 60 min and 80 ℃ for 30 min were more benefits beneficial to the retention of aroma substances in the tea infusions, thereby reducing the bitterness and astringency. According to the nutritional quality, taste, and aroma, the optimal combination of 80 ℃ for 30 min was recommended as the daily drinking brewing for XBT. The finding can also provide a theoretical basis for the subsequent processing of tea beverages. In short, the bud can be expected to serve as a tea products for the high economic value of Xanthoceras sorbifolium.