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Exercise 5.   Determination of the Anthocyanin Concentration in Table Wines and Fruit Juices Using Visible Light Spectrophotometry


A. Introduction

Image Source: Yakima Blueberries

Anthocyanins are natural plant pigments that give various fruits, vegetables and flowers red, blue and purple color. Blueberries, blackberries, raspberries and grapes, and wines and fruit juices made of these fruits are relatively rich in anthocyanins. Unlike chlorophylls and carotenoids, anthocyanins are water soluble; they are considered one of the largest and most important group of water-soluble pigments in the plant kingdom.

Anthocyanins are relatively strong natural antioxidants. They have recently caught the attention of scientists and the public because of their possible use in fighting the effects of aging and reducing the risk of cancer and cardiovascular disease through their antioxidant power. In recent years, research into the cellular effects of anthocyanins has intensified, and many research groups are working to determine the concentration of anthocyanins in fruits, vegetables, fruit juices, and wines.

The specific objective of the experiment to be performed in this exercise is to determine the concentration of anthocyanin pigment in various wines and fruit juices. To accomplish this objective, students will use a variety of pipets to prepare various standards and samples. Once these samples are prepared, students will employ visible-light spectrophotometry to measure the amount of anthocyanin pigment in samples. In the process, students will gain a working understanding of pipeting and spectrophotometry, two tools commonly used in cell biology, biochemistry and molecular biology laboratories.