Functional performance of a resistant starch ingredient modified using a microfluidiser

The effects of microfluidisation on a suspension of a resistant starch ingredient (high-amylose corn starch with 58% resistant starch) in water, that was previously heated (121 °C/60 min) and subjected to shearing using a Silverson Mixer, was examined. Heating and shearing starch suspensions, with or without a subsequent microfluidisation treatment, caused a reduction in the resistant starch content to ~ 30%. There was a decrease in the estimated molecular weight of the starch due to scission of the starch molecules following heating and shearing of the starch suspension and a further reduction with the subsequent microfluidisation of this suspension. Heating and shearing of the starch suspension increased its viscosity. The combined use of heat treatment, shearing and microfluidisation further significantly increased the viscosity of starch suspensions, depending on the pressure used during microfluidisation and the number of passes. The performance of the treated starch suspensions in stirred yoghurts was investigated to assess their ability to contribute to the physical properties in this application. Substitution of 3% milk solids in yoghurts (12% total solids) with heated, sheared and microfluidised starch suspensions significantly (p < 0.05) increased the viscosity and decreased syneresis of yoghurts but the incorporation of starch that had only been heated and sheared without microfluidisation did not. The results indicate that a treatment process for resistant starch which incorporates microfluidisation could potentially produce a new functional resistant starch ingredient with increased viscosity and water-holding properties.Industrial relevanceResistant starches have an important role in human health and are sought-after ingredients for functional foods, i.e. foods with benefits beyond normal nutrition. The incorporation of resistant starches into processed foods is often a challenge as the added starch can detract from the texture of the food. A limitation is the inability of most resistant starches to build viscosity. Our research has shown that it is possible to make a physically functional resistant starch ingredient by the application of physical processes to a starch suspension. This chemical-free process enables the production of a differentiated resistant starch ingredient that has the ability to build viscosity and contribute to the texture of a finished food product. It provides a potential solution for the incorporation of resistant starch into processed food products.