Appropriate addition of oat β-glucan improving rheological properties of dough

Abstract: Oat β-glucan, one of the non-starch polysaccharides, consists of long, linear chains of 30% β (1→3) and 70% β (1→4) linked D-glucopyranosyl residues and has been widely applications due to its outstanding functional and nutritional properties. One of its most important processing characteristics is the high water holding capacity and viscosity-forming potential which can be used as thickeners, emulsifiers and stabilizers to improve the texture and flavor in the food industry. In addition to the function as soluble dietary fibre, oat β-glucan has been associated with lots of other health benefits including better regulation of blood glucose and insulin levels, lowering of blood cholesterol levels and reducing the risk of heart disease. The potential use of β-glucans as texture improvers and fibre-enriching agents in bakery products to enhance consistency, resistance to deformation and elasticity of dough and to increase health benefits of products, has been reported by different authors. Chinese steamed bread flour and other 3 kinds of flours including low-gluten flour, medium-gluten flour and high-gluten flour dough that differ in the protein, are popularly used to make the staple food, for example, Chinese steamed bread, bread, dumpling and cookies, and have been recognized as the most efficient carriers for food special function strengthening of food to eliminate the deficiency of food functional factors and to meet the demand of customers. In this paper, the effects of 0.5%~5.0% of β-glucan from oat on the rheological properties, such as dough farinograph, tensile and pasting properties, of four different flour doughs formula, including low-gluten flour dough, medium-gluten flour dough, high-gluten flour dough and Chinese steamed bread flour dough, have been examined. The results showed that the farinograph water absorption rate of four doughs linearly increased with increasing contents of oat β-glucan. The addition of β-glucan to the dough formula increased the development time and the stability time and decrease their weakening degree. The addition of 0.5%~2.0% of oat β-glucan enhanced the maximum tensile resistance of four kinds of doughs, whereas 4.0%~5.0% of oat β-glucan reduced their maximum tensile resistance, extensibility and tensile energy. The addition of oat β-glucan decreased the peak viscosity, the hold viscosity, the final viscosity and the setback value of four kinds of doughs except the low-gluten flour dough formula with 2.0% or 4.0% of oat β-glucan addition and the high-gluten flour kinds of dough formula with 4.0% of oat β-glucan addition. The addition of oat β-glucan exhibited a significant decrease in the retrogradation value of all the dough formula. The addition of oat β-glucan to the dough formula increased the development time, the stability time, the weakening degree, the extensibility and the pasting temperature of the low-gluten flour dough, exceeding even that of the high-gluten flour dough. The reason that the change of rheological properties of dough fortified with oat β-glucan may be related to the high amount of water absorption and swelling of oat β-glucan subsequently forming of a net structure which increased the formation of hydrophobic interactions and disulfide bonds of gluten and surrounded the starch granules thus lowing the water the amount of water imbibed by the particles and preventing them from aging, which would help to extend the shelf life of flour products, such as bread, Chinese steamed bread, dumpling, and so on.