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Antioxidant activity of health tea infusions and effect of sugar and milk on in-vitro availability of phenolics in tea, coffee and cocoa drinks

Israel Olusegun Otemuyiwa (Department of Chemistry, Obafemi Awolowo University, Ile-Ife, Nigeria)
Mary Funmilayo Williams (Department of Chemistry, Obafemi Awolowo University, Ile-Ife, Nigeria)
Steve Adeniyi Adewusi (Department of Chemistry, Obafemi Awolowo University, Ile-Ife, Nigeria)

Nutrition & Food Science

ISSN: 0034-6659

Article publication date: 10 July 2017

Abstract

Purpose

Tea contains high content of phenolics which are well-known to act as antioxidants. As such, there are claims that the consumption of infusion of tea could help ameliorate free radical-induced diseases; this therapeutic activity would depend on the amount of phenolics that is soluble and the amount that is absorbed and available for metabolic activity when consumed. The purpose of this study is to analyze the content of phenolics and antioxidant activity of some health tea and also to study the effect of addition of sugar and milk on in-vitro availability of phenolics in tea, cocoa and coffee drinks.

Design/methodology/approach

Seven brands of health tea, two brands of cocoa drink, one brand each of coffee, powdered milk and sugar were selected. The tea samples were analyzed for pH, titratable acidity, total phenol and antioxidant activity using Folin–Ciocalteau and 202-diphenyl-1-picryl-hydrazil 28DPPH-29-20 reagents. In-vitro simulated digestion modeling stomach and small intestine were carried out on tea infusion, coffee and cocoa drinks with or without sugar, and phenolic availability was analyzed.

Findings

The result indicated that pH, titratable acidity and total phenolics ranged from 4.5 to 5.6, 0.167 to 0.837 (as maleic acid) and 1.15 to 1.17 mg/g gallic acid equivalent, respectively. Black tea recorded the highest phenolic content, in-vitro phenolic availability and antioxidant activity. Addition of sugar to black tea and chocolate drink caused a significant decrease in the in-vitro available phenolics, while the addition of milk leads to a significant enhancement.

Research limitations/implications

The data obtained in this study can be used nutritionally and commercially to show the impact of adding sugar or milk on the content of phenolics and their bioavailability in-vitro. The study justifies the claim that tea could help ameliorate free radical-induced health defects.

Practical implications

Assessment of antioxidant activity of food should not be based only on the content of total phenolics but on the amount that is bioavailable in the body system when the food is consumed.

Social implications

Consumption of tea, cocoa and coffee drinks with milk and sugar have been found to enhance or inhibit phenolics. Therefore, the optimum level of these additives should be determined if the drinks were meant for therapeutic purposes.

Originality/value

Results obtained may provide some useful information for considering the bioavailability of phenolics present in tea and beverages in view of consumption/digestion in our body as well as interference of sugar and milk as the additives.

Keywords

Acknowledgements

The authors hereby acknowledged the Department of Chemistry and the Central Laboratory of Obafemi Awolowo University, Ile-Ife, Nigeria for the opportunity to make use of some equipments during the analysis. This research was self-financed; no aid either in cash or kind was received from any organization.

Citation

Otemuyiwa, I.O., Williams, M.F. and Adewusi, S.A. (2017), "Antioxidant activity of health tea infusions and effect of sugar and milk on in-vitro availability of phenolics in tea, coffee and cocoa drinks", Nutrition & Food Science, Vol. 47 No. 4, pp. 458-468. https://doi.org/10.1108/NFS-08-2016-0134

Publisher

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Emerald Publishing Limited

Copyright © 2017, Emerald Publishing Limited