Effects of Infusion Time and Addition of Milk on Content and Absorption of Polyphenols from Black Tea

Abstract

Epidemiological studies assessing the health benefits of drinking black tea are equivocal. Such disparity may reflect an inability of semiquantitative assessment to consider how infusion time and addition of milk affect the bioavailability of potentially beneficial antioxidant polyphenols. Six brands of tea demonstrated similar increases in antioxidant capacity and total phenolic and catechin contents with increasing infusion time. These results were unaffected by the addition of milk. Consumption of black tea (400 mL) was associated with significant increases in plasma antioxidant capacity (10%) and concentrations of total phenols (20%), catechins (32%), and the flavonols quercetin (39%) and kaempferol (45%) (all p < 0.01) within 80 min. This was unaffected by adding milk. Infusion time may therefore be a more important determinant in the absorption of polyphenols from black tea. Observational studies assessing the health benefits of tea consumption require recording of brewing methods as well as frequency of consumption.

Associations between dietary flavonoid intakes and bone health in a scottish population

“…However, a bioavailability study examining the effects of infusion time and addition of milk to tea found that while greater infusion time increased the antioxidant capacity and phenolic content of tea, adding milk had no effect on these parameters. (39) In this study, femoral neck BMD was associated with all groups of flavonoids except flavones. This dietary factor explained a small amount of the variation (<1%); it is similar to that found for other key nutrients and greater than that explained by physical activity, a factor that has been shown to be important in the maintenance of bone mass.…”

“…One particular concern in this study is the lack of information in the FFQ about the type of tea drunk and the length of infusion time because these factors are known to affect the concentration of flavonoids in tea. (39) FFQs, despite inaccuracies, can be used to classify people into groups of intakes, and this ranking is the essential factor when studying diet and disease. (40) A further limitation of this study is the flavonoid database, which used two sources of composition data.…”

Oolong tea does not improve glucose metabolism in non-diabetic adults

“…The study of Hosoda et al (2003) suggested that oolong tea may provide beneficial effects, whereas the present study did not. It has also been speculated that tea infusion time and polyphenol or catechin content may contribute to the disparity in results of intervention studies (Kyle et al, 2007). Previous studies have provided a wide range of polyphenols, reportedly from 300 mg (MacKenzie et al, 2007b) to 1490 mg/day (Hosoda et al, 2003).…”

Evaluation of Antioxidant Profile and Phytochemical Constituents of Some Herb-Supplemented Black Tea Infusions

“…A plethora of evidence suggests that tea components including bioflavonoids and tannins are highly effective in scavenging free radicals [19]. However, brewing time and the addition of milk to tea infusions cause a profound reduction in affectivity of the drink [6]. To overcome such shortcomings, tea infusions are often mixed with different herbs during or after brewing.…”

“…Consequently, the antioxidant potential of milk tea is much reduced. In recent years there has been more and more research on the effect of consumer preparation on composition and activity of tea infusions [6][7]. The studies have examined the different culinary methods used in the domestic preparation of tea infusions, taking into account factors such as water temperature, infusion time, stirring and usable forms like loose-leaf tea and tea bags.…”