Effects of green tea extract on soy bread physical properties and total phenolic content
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Date
2007-08
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Publisher
The Ohio State University
Abstract
Soy and green tea contain antioxidants that may be used as health promoting ingredients. Various foods currently available on the market incorporate these ingredients individually but few contain a combination of soy and green tea in one product.
Since highly acceptable soy bread has been developed, the objective was to optimize the level of green tea addition to the soy bread. The physico-chemical properties of the bread and total phenolics were used as indicators of optimal quality.
A 900 gram loaf of plain soy bread was used as control. 0, 50, 100 and 150 mg of green tea extract per 100 g of soy flour were added. pH, water activity (aw), color (Lab values) and hardness (Instron) were measured in all samples. The total phenolics in soy bread extracts were determined spectrometrically according to the Folin- Ciocalteu colorimetric procedure and expressed as mg of gallic acid equivalents (GAE) per gram dry weight.
aw, pH and average bread hardness of the crumbs did not show significant differences across the control and the green tea extract fortified soy bread; with the average aw of 0.94, pH of 5.6 and average bread hardness of 3.8 kgf. A decrease in b (decrease in yellowness) and L (increase in darkness) values of the crumbs was observed upon increased addition of the green tea extract. Total phenolics in all samples ranged from 27.45 ± 1.82 mg GAE/g dry weight to 30.38 ± 0.84 mg GAE/g, demonstrating high total phenolic content but no significant changes between treatments.
Results showed that the green tea fortified soy bread was similar to the regular soy bread in terms of the texture, pH and moisture. The amount of green tea per 100 g of flour was too small for a significant increment in total phenolics. However, green tea extract darkened the bread crumbs and reduced visual appeal. Color intensity is an important factor relative to total phenolics in future development of the product. Apart from the color intensity, the addition of the extract did not aversely affect the physico-chemical quality of the soy bread. Sensory acceptability of the product is planned for future studies.
Advisor: Yael Vodovotz
Description
Instistute of Food Technologist Student Association Undergraduate Research Paper Competition Finalist
Keywords
antioxidants, functional food, total phenolic, green tea, soy bread, isoflavone