Manipulation of the Phenolic Quality of Assam Green Tea through Thermal Regulation and Utilization of Microwave and Ultrasonic Extraction Techniques

Abstract

The aim of this study was to investigate the catechin levels and antioxidant activities as manipulated by roasting temperature and roasting time of green tea. Roasting temperature and time varied between 100–300 °C and 60–240 s in green tea production. The main interactions measured were effects on the antioxidant activities, total phenolic content, DPPH, ABTS, FRAP and catechin content (catechin (C), epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG) and epicatechin (EC)). Optimum roasting conditions were determined as 270 °C for 240 s, since this enabled high catechin contents, antioxidant activities and production yield. The extraction methods for green tea including traditional extraction (TDE), microwave-assisted extraction (MAE) and ultrasonic-assisted extraction (UAE) using 60% ethanol as solvent were investigated to evaluate the highest bioactive compound and yield of extraction. MAE was found to be more efficient in green tea extraction compared to UAE and TDE. The extracts showed significant cytotoxic potential against the Huh-7 cell line, in concentrations ranging from 31.25 to 1000 µg/mL. The results are useful in understanding the relationship between thermal treatment and extraction conditions on the chemical and nutritional properties of tea catechins, making it possible to select the production and extraction conditions that maximize the levels of beneficial tea ingredients.

Effect of Leaf Grade on Taste and Aroma of Shaken Hunan Black Tea

“…The fragrance of geraniol exhibited a refined and pleasant rosy and sweet scent, and it demonstrated the highest OAV in first-grade black tea with agitation, suggesting its significance as a crucial aroma-active compound. Furthermore, geraniol also serves as a significant aroma component in various other tea varieties, including green tea, white tea, and oolong tea [ 32 , 33 , 34 ]. Methyl jasmonate, primarily derived from the metabolic pathway of linolenic acid, plays a pivotal role as a floral component in shaken Hunan black tea with agitation and serves as an endogenous signaling molecule in the plant’s defense response [ 35 ].…”

Impact of Green Extraction on Curcuminoid Content, Antioxidant Activities and Anti-Cancer Efficiency (In Vitro) from Turmeric Rhizomes (Curcuma longa L.)

“…The turmeric was extracted at 800 W for 3 min. The extraction was performed in cycles with 30 s of irradiation and 5 min of cooling time to control a temperature of 25 °C and to avoid solvent boiling [ 19 ].…”

“…Dulbecco’s Modified Eagle Medium (DMEM) with the addition of 10% fetal bovine serum, penicillin (100 IU/mL) and streptomycin (100 IU/mL) were used for the culture of Huh-7 and HCT-116 at 37 °C, following previously published methodology [ 19 ], and cells were harvested at 80–90% confluence.…”

Development, characterization, and consumer acceptance evaluation of thermally stable capsule beads containing mixed extracts of green tea and turmeric

“…Fresh green tea leaves (Raming Tea Co., Ltd, Chiang Mai, Thailand) were withered, roasted, rolled, dried, and milled using a hammer mill (Brook Crompton Series 2000, Hudders eld, UK) and passed through a 1.2 mm sieve. The extraction was undertaken following the protocol described in our previous studies 23 . Brie y, 100 g of green tea powder was extracted in 60% (v/v) of ethanol (1000 mL) using microwave-assisted extraction at 600 W for 10 minutes.…”

“…protocol used was in these measurements as described in our previous study 23 . A standard solution of curcuminoid was prepared by mixing curcumin (80%), DMC (17%) and BDMC (3%) (Sigma, St. Louis, MI, USA).…”