RESUMEN
Tea infected with bird's eye spot disease generally imparts a long-lasting bitter taste, which is unacceptable to most consumers. This study has comprehensively evaluated the taste profiles of infected and healthy teas and investigated their known bitter compounds previously reported in tea. Quantification analyses and calculation of dose-over-threshold (DoT) factors revealed that no obvious difference was visualized in catechins, caffeine, bitter amino acids, and flavonols and their glycosides between infected and healthy tea samples, which was also verified by principal component analysis (PCA) and hierarchical cluster analysis (HCA). Therefore, these known bitter compounds have been ruled out as critical contributors to the long-lasting bitterness of infected teas. Furthermore, Gel permeation chromatography, sensory analysis, and UPLC-Q-TOF-MS were employed and identified 13 substances from the target bitter fractions, including caffeine, ten triterpenoids, and two oxylipins. The higher triterpenoid levels were supposed to be the reason causing the long-lasting bitterness. This study has provided a research direction for the molecular basis of the long-lasting bitterness of infected tea leaves with bird's eye spot disease.
Asunto(s)
Cafeína , Triterpenos , Cafeína/análisis , Gusto , Triterpenos/análisis , Glicósidos/análisis , Té/químicaRESUMEN
Processing method is considered as a major factor that affects biotransformation of phytochemicals in tea and leads to diverse flavor and bioactivity of tea. In the present work, six typical tea manufacturing processings were employed to compare the effect on chemical composition of teas through using leaves of the single tea cultivar - - Camellia sinensis var. Meizhan. And in vitro antioxidant activity, inhibition against α-glucosidase and three lipid metabolism enzymes of these teas were also investigated, the relationships among them were analyzed further. As fresh leaves were processed into six categories of teas, the content of total catechins (TCs) has decreased in varying degrees while theaflavins (TFs) has increased. The antioxidant capacity composite index (ACCI) from high to low were green tea, yellow tea, oolong tea, white tea, dark tea, and black tea with the range from 98.44 to 58.38, which dominated by the content of TCs. Furthermore, all categories of teas possessed an inhibition effect on the pancreatic lipase (PL), 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-COA reductase), lecithin cholesterol acyltransferase (LCAT), and α-glucosidase. The inhibition rate of PL and α-glucosidase appears to be positively influenced by TFs content (r =0.863, r =0.857, p < 0.05) while that of LCAT showed significant positive correlations with the content of tea polyphonels (TPs) (r = 0.902, p < 0.01). These results provide a better understanding of the relationships between processing method and chemical components of tea. It is suggested that various tea categories possess potential healthy effects which could serve as promising nutritional supplements.[Figure: see text].
Asunto(s)
Camellia sinensis/química , Fitoquímicos/análisis , Antioxidantes/análisis , Inhibidores de Glicósido Hidrolasas/farmacología , Metabolismo de los Lípidos/efectos de los fármacos , alfa-Glucosidasas/metabolismoRESUMEN
To explore the relationship between the moisture content of withered tea leaves and their physical properties (i.e., elasticity, plasticity, flexibility, and texture) during withering, texture analyzer was employed to test the elasticity and flexibility of withered tea leaves with different moisture contents. The texture was evaluated by computer vision technology. The withered tea leaves with different moisture contents were used to process congou black tea, which was then subjected to sensory evaluation. Results showed that good elasticity, optimal flexibility, and plasticity were achieved when the moisture content of the withered tea leaves of Fudingdabai comprising two leaves and one bud varied arranging from 65.51 to 61.48%. The sensory evaluation of congou black tea revealed that moderate withering was better than long-term withering and that both moderate and long-term withering were better than no withering during processing. The moisture content was significantly correlated with the flexibility and plasticity of the withered tea leaves. Fresh tea leaves undergoing moderate withering with moisture content of 65.51-61.48% to process congou black tea, good tea shape and liquor color were achieved. This study provided new evidence that the moisture content of withered tea leaves significantly affected the quality of black tea.