This study was undertaken in order to investigate the effects of different drying temperatures (60, 70, 80, 90 and 100 ℃) on the quality of pressed white tea cake made from withered leaves. Various quality components of white tea cake such as aroma, sugar components, polyphenols and amino acids were analyzed using targeted metabolomics based on headspace solid-phase microextraction combined with gas chromatography-time-of-flight mass spectrometry (HS-SPME-GC-TOF-MS). The results showed that the sensory quality score of white tea cake increased first and then decreased with increasing drying temperature, reaching its maximum (90.2) at 80 ℃. The total catechin content of white tea cake dried at 80 and 90 ℃ was significantly lower than that of white tea cake dried at 60, 70 and 100 ℃ (P < 0.05). The contents of total amino acids and refreshing taste amino acids in white tea cake dried at 80 ℃ were significantly higher than those in white tea cake dried at 70 ℃ (P < 0.05). The sugar contents of white tea cake dried at 70 and 80 ℃ were significantly higher than those of white tea cake dried at low temperature (60 ℃) and high temperature (90 and 100 ℃) (P < 0.05). The main volatile substances of white tea cake were generally consistent across all drying temperatures, in which alcohols accounted for a large proportion. The contents of ester aroma substances such as methyl tridecanoate, methyl octanoate, methyl nonanoate and acetic acid lactone in white tea cake dried at 80 ℃ were significantly higher than those in white tea cake dried at 90 and 100 ℃ (P < 0.05). In general, drying at 80 ℃ can improve the refreshing taste and sweetness of pressed white tea cake and the content of pleasant aroma substances, thereby conducing to the quality formation. The appropriate drying temperature for pressed white tea cake, therefore, is 80 ℃. The results can provide reference for the processing technology of white tea cake pressed by withered leaves.

In order to explore the quality characteristics and components of Jiulong Dabaicha, a type of white tea, we made white tea from six varieties, Jiulong Dabaicha, Fuan Dabaicha, Fuyun 6, Zhenghe Dabaicha, Fuding Dabaicha and Songxi Caicha and comparatively analyzed their quality using sensory evaluation, biochemical analysis, high performance liquid chromatography (HPLC), headspace-solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). The results showed that each variety of white tea had their own characteristics, showing good sensory quality. The buds of Jiulong Dabaicha were particularly plump and shiny; the color was gray-green with a moist appearance; the infusion had a bright apricot yellow color, a fresh and tender aroma with floral and pekoe notes, and a fresh, mellow, sweet and refreshing taste; the leaf base was soft and tender. Among the six varieties, the contents of total catechin, ester catechin, epicatechin gallate, theanine, glutamic acid and arginine in Jiulong Dabaicha were the highest, 102.52, 96.31, 71.29, 11.00, 0.68 and 1.07 mg/g, respectively. A total of 38 differential aroma compounds between the six varieties were identified. Jiulong Dabaicha had the highest content of alcohol compounds, with significantly higher levels of phenylethyl alcohol, hexanoic acid (both responsible for rosy aroma) and (Z)-3-hexen-1-ol (fresh floral aroma) and significantly lower levels of ethylbenzene (gasoline odor), 2-acetylpyridine (barbecue flavor), and naphthalene (spicy flavor) compared to the other varieties. Our results are helpful to elucidate the flavor and quality characteristics of Jiulong Dabaicha, providing a scientific basis for product development and promotion of Jiulong Dabaicha.