Determining the effects of tencha-ro drying on key volatile compounds in tencha (Camellia sinensis) through gas chromatography-mass spectrometry.

Drying is the key process through which the aroma of tencha forms. However, the effects of drying method on volatiles are unknown. We compared tencha-ro drying with regular drying. Volatiles in tencha infusions were extracted using headspace solid-phase microextraction and solvent-assisted flavor evaporation combined with gas chromatography-mass spectrometry. Partial least squares (PLS), odor activity value (OAV), and heat map analyses were performed to identify the optimal drying method for creating a seaweed-like aroma. Changes in the key volatile compounds of the samples were investigated. The tencha infusions contained 125 volatiles with nine chemical structures. According to the sensory evaluation, tencha-ro drying was the optimal method for producing high-quality tencha with an intense and consistent seaweed-like aroma. The PLS model accurately distinguished among the types of tencha. By combining OAVs with screening through multivariate statistical analysis, six volatile compounds were revealed to contribute substantially to tencha's seaweed-like aroma: 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-6-methylpyrazine, 2-ethyl-5-methylpyrazine, dimethyl sulfide, ß-ionone, and 2-formyl-1-methylpyrrole. The findings provide a theoretical basis and technical guidance for the processing of high-quality tencha with a strong seaweed-like aroma. PRACTICAL APPLICATION: This study demonstrated that tencha-ro drying contributes to the formation of a seaweed-like aroma in tencha and provides theoretical guidance for tea factories to use the appropriate drying methods for high-quality tencha.

Quality chemical analysis of crush-tear-curl (CTC) black tea from different geographical regions based on UHPLC-Orbitrap-MS.

Crush-tear-curl (CTC) black tea is a popular beverage, owing to its unique taste characteristics and health benefits. However, differences in the taste quality and chemical profiles of CTC black tea from different geographical regions remain unclear. In this study, 28 CTC black tea samples were collected from six geographical regions and analyzed using electronic tongue and ultrahigh performance liquid chromatography-Orbitrap-mass spectroscopy. The e-tongue analysis indicated that each region's CTC black tea has its own relatively prominent taste characteristics: Sri Lanka (more umami and astringent), North India (more umami), China (more sweetness and astringent), South India (moderate umami and sweetness), and Kenya (moderate umami and astringent). Based on multivariate statistical analysis, 78 metabolites were tentatively identified and used as potential markers for CTC black tea of different origins, mainly including amino acids, flavone/flavonol glycosides, and pigments. Different metabolites, which contributed to the taste characteristics of CTC black tea, were clarified by partial least squares regression correlation analysis. Our findings may serve as useful references for future studies on origin traceability and quality characteristic determination of CTC black teas. PRACTICAL APPLICATION: This study provides useful references for future studies on the origin traceability and taste characteristic determination of CTC black teas from different geographical regions.

Targeted and nontargeted metabolomics analysis for determining the effect of storage time on the metabolites and taste quality of keemun black tea.

The black tea could be stored for a long time, and subsequently affects the flavor characteristics. In the present study, the effects of storage years (1, 2, 3, 4, 5, 10, 17 and 20 years) on the chemical profiling and taste quality of keemun black tea (KBT) were compared by metabolomics and quantitative sensory evaluation. The main polyphenols were degraded during the storing, especially 10-year storage, but caffeine and theobromine were stable. The intensity of bitterness, astringency, umami was negatively correlated to storage years, with correlation coefficient at -0.95, -0.91 and -0.83 respectively, whereas sweetness had positive correlation coefficient at 0.74. Quinic acid, galloylated catechins, linolenic acid, linoleic acid, malic acid, palamitic acid, and theaflavin-3́-gallate were marker compounds which were responsible for distinguishing short and long time preserved KBT. The contents of fatty acids were positively correlated to storage time and sweet intensity.

Effects of stem removal on physicochemical properties and sensory quality of tencha beverages (Camellia sinensis; Chuanxiaoye).

Fresh tea leaves (Camellia sinensis; Chuanxiaoye) used to make tencha tea are a combination of the stem and leaf. Tencha made from the leaf alone is considered a high-quality tencha beverage with a seaweed-like aroma, mellow taste, and a green appearance. However, no study has investigated the differences between these two variants. In this study, the effects of stem removal on physicochemical properties and sensory quality of tencha beverage were investigated. The appearance feature, taste, and aroma were evaluated, and the results indicated that stem removal improved the quality of tencha beverages. The water extract, total free amino acids, total catechin, epigallocatechin gallate, caffeine, and chlorophyll were higher in leaf-only tencha (LOT) than in leaf and stem tencha (LST), whereas the crude fiber and phenol ammonia ratios were lower in LOT than in LST. Principal component analysis and hierarchical clustering analysis further discriminated between the tencha beverages with different stem contents. This study provided a theoretical basis for quality control by adopting a stem-leaf separation process in tencha manufacturing. PRACTICAL APPLICATION: This research provides theoretical guidance for improving tencha quality during manufacturing.