Production and Polyphenolic Composition of Tea

Abstract

Tea (Camellia sinensis) is the second most commonly consumed beverage in the world, and its consumption has been associated with several important health benefits due in part to its high concentration of polyphenolic compounds. Tea varieties, including white, green, oolong, pu-erh, and black tea, are all produced from the same plant but differ in postharvest processing. The level of oxidative processing from white to black tea (low to high) drives changes in polyphenol profiles from monomeric polyphenols (catechins) to oxidative products (theaflavins and thearubigins) that convert the subtle yellow color of green tea to the distinctive red/copper color of oolong and black tea. Poly-phenol compounds from green teas have been well studied; however, oxidative products are more difficult to characterize and may require a combination of analytical techniques for identification and quantification. This technical summary introduces the major polyphenols in tea and discusses the main steps of tea processing and instrumentation used for polyphenol analysis.

Dose–Response Relation between Tea Consumption and Risk of Cardiovascular Disease and All-Cause Mortality: A Systematic Review and Meta-Analysis of Population-Based Studies

“…Development of novel biomarkers of exposure for future research would assist researchers in overcoming measurement error from assessing tea consumption via FFQs. The amount of flavonoids consumed in tea beverages depends on several factors, including the following: 1) their concentration in the tea leaves; 2) the mass of tea leaves used to prepare the infusion; 3) the volume of water used to prepare the infusion; 4) the water temperature, brew time, and agitation used to prepare the infusion; 5) the pH of the water used to prepare the infusion, thermal processing (for commercial tea infusions), and duration between preparation and consumption; and 6) the volume of the infusion consumed, as reviewed and described by Ho and colleagues (71). Lastly, due to multiple testing in subgroup analyses that increased the risk of type I error (false positive), the findings from subgroup meta-analyses and meta-regression analyses should be interpreted with cautions as they are mainly for hypothesis generating purpose.…”

Impact of thermal processing on the nutrients, phytochemicals, and metal contaminants in edible algae

“…Because characterization of individual phenolic compounds in algae is ongoing, studies on how processing affects phenolic compounds in algae have generally used non-specific assays that determine total rather than individual concentrations of these compounds (Charles, Sridhar, and Alamsjah 2020, Badmus, Taggart, and Boyd 2019, Ling et al 2015. The Folin-Ciocalteu method and other nonspecific assays are commonly used to estimate total phenolic compounds in foods and extracts, but they do not provide the selectivity and specificity needed to differentiate phenolic compounds of different classes (Ho et al 2018). Total phenolic compounds in fresh algae determined using Folin-Ciocalteu's reagent has ranged from a low of less than 1 mg gallic acid equivalents (GAE) per 100 g dulse up to 230 mg/100 g GAE for algae in genus Himanthalia (Ferraces-Casais et al 2012, Jacobsen et al 2019.…”

Short-Term Tea Consumption Is Not Associated with a Reduction in Blood Lipids or Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

“…A substantial body of evidence also supports the role of flavan-3-ols in modulating enzymes involved with oxidative damage, inflammation, and platelet activation (5). The flavan-3-ol content of teas vary due to environmental growing conditions, leaf processing, and tea preparation methods (2,3).…”

“…Tea (Camellia sinensis), with its >5,000 year history, is the most commonly consumed beverage worldwide aside from water (1,2) and is a primary source of flavan-3-ols in the diet (2). Based on how the leaves are processed (i.e., with or without, and the degree of fermentation), tea can be categorized into black (fermented), oolong (partially fermented), or green (unfermented) (3). Flavan-3-ols (predominantly catechins, theaflavins, and thearubigins) are the main dietary bioactive compounds present in tea.…”