Journal Articles

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Start date: 2023Subject: search.filters.subject.Catechins

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    Development of a validated efficient HPLC-DAD analysis for assessing polyphenol transformation during black tea processing
    (Elsevier Inc, 2025-12-01) Muthulingam P; Popovich DG; Nimal Punyasiri PA; Nanayakkara CM; Mesarich CH; Rashidinejad A
    Tea (Camellia sinensis) is valued for its polyphenolic compounds, which define its sensory and health attributes. Accurate quantification across processing stages is hindered by analytical and extraction challenges. We developed and validated a rapid high-performance liquid chromatography with diode array detection (HPLC-DAD) method for simultaneous analysis of 12 key constituents - gallic acid, theobromine, caffeine, (+)-catechin (C), (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate (ECG), theaflavin (TF), theaflavin-3-gallate (TF3G), theaflavin-3′-gallate (TF3’G), theaflavin-3,3′-digallate (TF3–3’G), in green and black tea. The method achieved superior linearity (r² > 0.9995), high sensitivity (LOD: 0.03–1.68 µg/mL), strong precision (RSD < 4.68 %), and high recovery, while also resolving co-elution with a 40-min runtime. Extraction was optimized using ultrasonication with 70 % methanol, which outperformed hot water and ISO-standard methods. Applied to black tea processing, the method revealed a 79.1 % reduction in catechins, post-rolling theaflavin peaks, and dynamic fluctuations in gallic acid, caffeine, and theobromine. These changes were associated with enzymatic oxidation, leaching, and cultivar effects. The validated HPLC-DAD method provides a robust tool for tea polyphenol profiling and enables improved understanding of processing-induced transformations. It holds potential for use in quality control, nutritional labeling, and functional food research in tea and other polyphenol-rich systems.
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    Starch digestibility of cooked rice as influenced by the addition of different tea types (Camellia sinensis): An in vitro study
    (Elsevier B.V., 2023-06-26) Apinanthanuwong G; Aumasa T; Ogawa Y; Singh J; Panpipat W; Donlao N
    The stability of tea catechin is influenced by various factors such as tea types, pH and digestive processes. The study aimed to investigate the effect of different tea types on the stability of tea catechin and their impact on starch digestibility and glycemic response to different types of cooked rice. Cooked rices were co-digested with green tea, oolong tea and black tea, and the catechin profiles were correlated with the inhibition of enzymatic digestion. The findings revealed that the green tea exhibited to be the most potent inhibitory effect on starch digestion. In addition, due to its highly porous structure, glutinous rice showed a higher starch hydrolysis rate and glycemic index than jasmine rice. The estimated glycemic index (eGI) of cooked jasmine rice co-digested with green, oolong, and black teas were 61.95 ± 1.07, 64.62 ± 1.12, and 67.14 ± 0.87, respectively, while eGI values of cooked glutinous rice were 77.55 ± 1.15, 79.98 ± 0.98, 81.45 ± 0.75, respectively. The findings indicates that epigallocatechin (EGC) achieves the highest stability. Overall, the results provided compelling evidence that tea types and rice structure affect the regulation of starch digestion and eGI of cooked rice.