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 com starch with 58% resistant starch) in water, that was previously heated (121 degrees 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 similar 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. Crown Copyright (C) 2007 Published by Elsevier Ltd. All rights reserved.