Effect of Fixation Methods on Biochemical Characteristics of Green Teas and Their Lipid-Lowering Effects in a Zebrafish Larvae Model

Abstract

Fixation is a key process contributing to different flavors of green tea and pan-fire and steam were the common fixation methods applied conventionally. In this study, pan-fired green tea (PGT) and steamed green tea (SGT) produced by different fixation methods were compared in characteristic biochemicals including volatile compounds, amino acids, catechins and alkaloids, together with evaluating their tastes and lipid-lowering effects. PGT and SGT could be distinguished clearly by orthogonal partial least squares discriminant analysis (OPLS-DA) and heatmap. SGT had higher contents of volatile alcohols (44.75%) with green and floral attributes, while PGT had higher contents of volatile esters (22.63%) with fruity and sweet attributes. Results of electronic tongue analysis showed that PGT and SGT had similar taste of strong umami and sweetness, but little astringency and bitterness. In addition, amino acids were more abundant in PGT (41.47 mg/g in PGT, 33.79 mg/g in SGT), and catechins were more abundant in SGT (111.36 mg/g in PGT, 139.68 mg/mg in SGT). Zebrafish larvae high-fat model was applied to study the lipid-lowering effects of PGT and SGT. Results showed that both SGT and PGT had lipid-lowering effects, and the lipid level was decreased to 61.11 and 54.47% at concentration of 300 mg/L compared to high-fat group, respectively. Generally, different fixation methods of pan-fire and steam showed significant effects on aroma and contents of characteristic chemical compounds (amino acids and catechins) of green tea, but no effects on the taste and lipid-lowering activity.

Effects of electromagnetic roller-hot-air–steam triple-coupled fixation on reducing the bitterness and astringency and improving the flavor quality of green tea

“…Fixation is the key process responsible for flavor formation in green tea. During fixation, the activity of the polyphenol oxidase enzyme is rapidly reduced at elevated temperatures, thereby preventing the oxidation of TPs and maintaining the green color of the tea and liquor ( Li et al, 2022 ). In addition, high temperatures promote the loss of moisture and grassy volatiles from the leaves, while generating and accumulating new aroma compounds and promoting the degradation of proteins and polysaccharides; this process is conducive to the accumulation of fresh-sweet taste substances, such as free amino acids and soluble sugars ( Wang et al, 2021 ).…”

Extraction of a Triterpene Solution and Evaluation of the Hypolipidemic Efficacy of the Pleurotus tuber-regium (Fr.) Sing Sclerotium

“…A zebrafish animal model was selected for the evaluation of the efficacy, and a high-fat model was established to analyze the in vivo hypolipidemic activity of total triterpenes from the PTRSS by assessing the lipid accumulation in zebrafish [ 23 , 24 ].…”

The Cultivar Effect on the Taste and Aroma Substances of Hakka Stir-Fried Green Tea from Guangdong

“…Six of the measured compounds, ECG, EGC, EGCG, GC, GCG, and theanine, differed significantly in all teas (Figure 2A), which suggested that they may have been the main non-volatile components shaping the taste differences among the three HSGTs. A multivariate statistical analysis, OPLS-DA, which amplifies between-group differences and minimizes within-group differences, was used to visually simplify the HPLC results [35][36][37]. The score plot (Figure 2B) shows that the three HSGTs were clearly distinct in terms of their non-volatile profiles.…”