Tea is the most consumed beverage in the world next to water. The total amount of tea produced and consumed in the world can be broken into 78% black, 20% green and < 2% is oolong tea. Black tea is consumed primarily in Western countries and in some Asian countries, whereas green tea is consumed primarily in China, Japan, India, and a few countries in North Africa and the Middle East. Oolong tea production and consumption are confined to southeastern China and Taiwan. There are three major classes of plant chemicals: terpenoids, phenolic metabolites, and alkaloids. Among these three groups, phenolic compounds are the most important for dietary applications and the most extensively researched.
Phenolic compounds include phenolic acids (hydroxybenzoic and hydroxycinnamic acids), polyphenols (hydrolyzable and condensed tannins), and flavonoids. These compounds protect plants, fruits, vegetables, and the humans that consume them from oxidative damage. Phenols are one of the main secondary metabolites present in plants. They are found in both edible and non – edible plants and have been reported to have many biological effects. Phenolic compounds are an extensively studied group of compounds that come from natural sources. Flavonoids are a type of phytochemical that possess a number of biological activities. They are the most common group of polyphenolic compounds that are found everywhere in plants. Flavonoids and other plant phenolics are common in leaves, flowering tissue and woody parts such as stem and bark (Gupta et al. 2012).
Antioxidants protect us from dangerous substances called free radicals that can lead to many chronic diseases. Antioxidants include secondary metabolites, enzymes and high/low molecular weight proteins that act against these free radicals. Phenolics from plants act as a source of natural antioxidants and have many functions including being reducing agents, metal chelators and quenchers of oxygen singlets (Shalini et al. 2010).
The purpose of this research project is to determine the phenol content and antioxidant properties of the water extracts of 12 commercially available teas. The results will then be evaluated and compared with one another. The total phenolic content will be determined by the Folin-Ciocalteu method with gallic acid used as the standard. The antioxidant properties will be evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay system. This project aims to determine which tea samples have the highest phenol content and antioxidant activity as well as further our understanding of these two properties of tea. To determine both phenolic content and antioxidant activity, UV – Vis spectroscopy will be used and the results will be tabulated in an Excel spreadsheet to observe any similarities or differences between the samples. This project is important to explore because tea is consumed by almost everyone worldwide. This research will be able to provide the public with more insight into how beneficial tea is to the human body.