Increasing consumer awareness of the health benefits of fruits and vegetables has prompted the development of bakery products containing whole wheat flour and the fortification of bakery products with fruits and vegetables with high antioxidant potentials.
Phenolic acid, a type of antioxidant, is abundant in whole grains and is present in high concentrations in cell walls and in the seed coat and embryo of wheat, which are removed during milling, but is not present in significant quantities in the endosperm. They are very effective antioxidants, known to mop up dangerous free radicals, thereby helping to prevent diseases such as cancer and heart disease.
As phenolic acids are vulnerable to conditions normally present in food processing, such as oxidation and degradation, exposure to light, oxygen and heat, this may accelerate the destruction of phenolic acids. Therefore, information on the stability of phenolic acids during food processing is important to evaluate the potential health benefits of foods containing phenolic acids.
A study that appeared in the March 2011 edition of the Journal of the Science of Food and Agriculture evaluated the effect of baking on the antioxidant activity of different phenolic acids. The study was triggered by the fact that, to date, no studies have been published on the effect of baking on the phenolic acid content and antioxidant activity of wheat flour.
Changes in the antioxidant potential of wheat flour when exposed to mechanical mixing, fermentation and baking were investigated. In this model, instead of adding vegetables and fruits as antioxidant sources, four different phenolic acids were added individually to the wheat flour and their antioxidant activities were determined at each step of the breadmaking process.
Four phenolic acids – caffeic acid, ferulic acid, syringic acid and gallic acid – were mixed with wheat flour at a concentration of 4.44 µmol/g of flour. The flour was then mixed into a dough until maximum elasticity was attained. It was divided into three portions. The first portion was dry frozen (lyophilised) immediately, the second was fermented and then lyophilised and the third was fermented, baked and then lyophilised.
The dough was fermented for 1 h at 30 °C and 85 ± 5 per cent relative humidity (RH) in a proofer. The fermented dough was then baked in the electrically heated deck oven, which had independently operated decks, at 200 °C (top) and 190 °C (bottom) for 20 minutes.
The lyophilised unfermented dough, fermented dough and bread were ground, sieved through a 20-mesh screen, sealed in plastic bags and frozen until analysis. The antioxidant potential of the acids was determined using the β-carotene-bleaching activity assay, and free phenolic acid levels were determined by high-performance liquid chromatography.
The researchers found that of the phenolic acids, caffeic acid had the most pronounced antioxidant effect, followed by ferulic acid, gallic acid and syringic acid. Also, their results showed the concentration of ferulic acid was the highest of the residual free phenolic acids after the baking process. Although less added caffeic acid was recovered than added ferulic acid, caffeic acid made the greatest contribution to the antioxidant activity of bread.
The authors concluded that phenolic acids retain their antioxidant activity after the baking process, and this has potential health benefits for consumers and the food industry in terms of the development of functional foods.
Source: Journal of the Science of Food and Agriculture
Published online ahead of print: DOI: 10.1002/jsfa.4188
Title: Antioxidant activity of hard wheat flour, dough and bread prepared using various processes with the addition of different phenolic acids
Authors: Hye-Min Han, Bong-Kyung
