Determination of tea fermentation degree by a rapid micellar electrokinetic chromatography

Determination of Catechins in Tea by Micellar Electrokinetic Chromatography With a Graphene Oxide-Coated Capillary

“…Compared with the determination of catechins in teas by CE, [21][22][23][24][25][26][27][28][29][30][31][32] the graphene oxide-coated capillary achieved the separation under acidic conditions, which promote the stability of the analytes. [7,29,33,34] Few papers have reported for the determination of catechins in acid.…”

“…[21][22][23] Micellar electrokinetic chromatography (MEKC) has been widely used for the analysis of tea. [24][25][26][27][28][29][30][31][32] Most of these reports were performed with neutral [24,[26][27][28] or alkaline buffers, [32] while few papers employed acidic conditions. [29][30] However, (-)-epigallocatechin gallate and epigallocatechin are unstable in alkaline solutions while the stability of catechins increased in acidic solution; [7,29,33,34] therefore, there is a need for an MEKC method using an acidic buffer for the separation.…”

Capillary electrophoresis determination of non-protein amino acids as quality markers in foods

“…It also has demonstrated to have an important role in different biological activities such as promoting relaxation, decreasing levels of serotonine and norepinephrine in brain, reducing blood pressure and enhancing anti-tumor activity [48]. A MEKC method using a BGE (pH 7.0) containing 10 mM phosphate, 4 mM sodium tetraborate, 45 mM sodium dodecyl sulfate (SDS), and 0.5% ethanol, and UV detection (205 nm and 266 nm) was developed by Hsiao et al [24] for the simultaneous determination of theanine, seven catechins, three xanthines, gallic acid, vitamin C and theaflavins in non-fermented, partially-fermented and fully-fermented tea samples. The successful separation of the studied compounds within 8 min enabled the application of the proposed method for the quality control of tea fermentation (in particular, the theanine content did not change significantly).…”

Analysis and modeling of major polyphenols during oxidation in production of black tea

“…Duration, temperature, and relative humidity of air and oxygen availability in the air during fermentation are crucial factors responsible for formation of high levels of desired products (Obanda, Owuor, & Mangoka, ; Tang et al, ) and their effect on the formation and depletion of the oxidized compounds and their correlation with sensory quality has been the subject of many studies (Asil, Rabiei, & Ansari, ; Muthumani and Senthil Kumar, ; Obanda et al, ; Owuor, Obanda, Nyirenda, & Mandala, ; Tang et al, ). In black tea manufacturing factories, end point of oxidation is mainly determined by experienced individuals and this usually affects the qualities of final product (Hasiao, Chen, & Cheng, ). Researchers have reported the fermentation duration at which TF content is maximum as optimum fermentation time (Emdadi, Nasernajad, Shokrgozar, Mehranian, & Vahabzadeh, ; Masoud, Bahram, & Farzaneh, ; Muthumani and Senthil Kumar, ; Tüfekci & Güner, ).…”