Comprehensive Investigation of the Effects of Brewing Conditions in Sample Preparation of Green Tea Infusions

Abstract

Chemical and biological investigation of green tea has been generally performed while using different infusions that are prepared without consideration of the effects of sample preparation conditions. In this study, for the first time, the effects of green tea brewing conditions on the antioxidant activity and chemical profiles of metabolome and catechin compounds were examined at 60 °C and 95 °C for a period of 5–300 min. The antioxidant capacities of the tea infusions, which were assessed as per 2,2-diphenyl-1-picryl-hydrazyl hydrate (DPPH) radical scavenging activity, depended more on temperature than time. Metabolomics study that was based on ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UHPLC-QTOF/MS) revealed that the metabolic profiles, including 33 differential metabolites, were significantly changed by temperature and time, with the effects of time being more evident at 95 °C starting after 30 min. Infusions that were brewed at 95 °C for greater than 30 min yielded distinct profiles in the hierarchical clustering analysis. The quantification of eight catechins by UHPLC-QqQ/MS showed that the total catechin level peaked at 95 °C brewing at 10 min, after which the levels of four epi-forms of catechins decreased and those of four non-epi-forms increased, implying the epimerization of catechins over time. These results suggest that the brewing conditions for sample preparation of green tea should be put into careful consideration in studies where green tea extracts are applied as aqueous infusions.

Green tea polyphenolic antioxidants oxidize hydrogen sulfide to thiosulfate and polysulfides: A possible new mechanism underpinning their biological action

“…pan-fired, oven-dried or steamed for heat inactivation, rolled vs non-rolled). Moreover, the composition of their aqueous extracts varies with brewing conditions [ [82] , [83] , [84] ]. Chinese green teas are slightly fermented and often sweet and lighter, with a lower polyphenol content and less of the grassy/umami flavor characteristic of Japanese green teas.…”

Quantification of Polyphenols and Metals in Chinese Tea Infusions by Mass Spectrometry

“…Nowadays, the detection of polyphenols in food matrices is based on standardized methods based on colorimetric, e.g., Folin–Ciocalteu assay, and HPLC-UV analyses [ 17 ]. Recently, the quantification of eight catechins by ultra-HPLC coupled to triple quadrupole mass spectrometer (UHPLC-QqQ/MS) used in multiple reaction monitoring (MRM) has been performed in green tea [ 18 ] or in black tea infusions for an in vivo bioavailability study on tea-consuming guinea pigs [ 19 ]. The MRM approach is widely applied in proteomics [ 20 ] or metabolomics investigations [ 21 ].…”

Effect of brewing conditions on the chemical and sensory profiles of milk tea

“…1 a, b). Increased temperature and increased tea in the mix might increase components correlated to bitterness, such as the alkaloids, catechins, anthocyanins, phenolic acids, flavonol glycosides, and theaflavins ( Jin et al, 2019 , Ye et al, 2022 , Zhang et al, 2017 ). Sweetness tended to be the opposite of bitterness, decreasing considerably when the temperature and tea: milk ratio increased ( Fig.…”