Abstract:
【Objective】To compare the effects of different baking times on the flavour quality of Beauty tea, which provided reference basis for the optimization of the baking process and quality improvement of Beauty tea. 【Method】Jinxuan and Qingxin Damao Beauty teas made by indoor natural withering and outdoor sunlight withering were used as materials. Quality analysis of Jinxuan and Qingxin Damao Beauty teas with different baking times was conducted using sensory evaluation and biochemical composition detection. Identification and analysis of volatile compounds in baked Beauty tea using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry(HSSPME-GC-MS) and Orthogonal Partial Least Squares Discriminant(OPLS-DA). 【Result】The sensory results showed that with the increase of baking times, the taste of the two types of Beauty tea soup became richer and smoother; the aroma of tea soup changed from a light fragrance to a light honey aroma, and then to a honey aroma, gradually forming the aroma characteristics of the fruit honey aroma and flower honey aroma of the Beauty tea. Analysis of biochemical results found that the polyphenols in outdoor withered Jinxuan and Qingxin Damao Beauty tea decreased from 24.225% and 20.461% to 22.210% and 19.015% respectively. In indoor and outdoor withered Qingxin Damao Beauty tea, with the increase of baking times, theabrownin content decreased from 2.540% and 2.801% to 2.343% and 1.967%. The contents of water extracts and theaflavins significantly increased in the second baked Jinxuan Beauty tea(
P<0.05). The results of volatile materials analysis showed that 151 volatile substances were identified in Beauty tea with different baking times, including 35alcohols, 25 aldehydes, 29 esters, 21 alkenes, 17 ketones, and 24 other substances. According to the OPLS-DA analysis, the substances with variable importance projection greater than 1(VIP>1) were screened as differentiated volatile substances, and it was found that 18 and 19 differentiated volatile substances were screened in the first and second baking of Jinxuan Beauty tea respectively, and 25 and 36 differentiated volatile substances were screened in the first and second baking of Qingxin Damao Beauty tea respectively. Among them, geraniol, phenylethanol, linalool,(Z)-oxo-linalool(furans), dihydro-linalool, benzaldehyde, and methyl salicylate were the key aroma compounds in different number of bakings, and the rise in their content formed the honey and floral-fruity aroma of the Beauty tea. After two bakings, the total content of aroma compounds in Jinxuan Beauty tea increased by 1.3 to 2.5 times, while the total content of aroma compounds in Qingxin Damao Beauty tea increased by 1.2 to 1.8 times. 【Conclusion】Baking helps to improve the flavor quality of Beauty tea, making its taste more mellow and soft, taste more smooth, the overall flavor quality has been greatly improved. After two bakings, beauty tea has better quality, more obvious honey aroma and more mellow taste.