Whey protein isolate regulates the oral processing characteristics of lotus root starch

Abstract

This study aimed to investigate the influence of different levels of added whey protein isolate (WPI) on the oral processing characteristics of lotus root starch (LRS). The IDDSI test results indicated that WPI-LRS composite gels could be classified as foods suitable for individuals with dysphagia. During in vitro oral digestion process, addition of WPI increased the viscosity of the composite system. When the amount of WPI reached 100% (w/w), the reducing sugar content decreased from 105.23 to 42.35 mg. Inverted fluorescence images revealed that WPI formed a continuous network structure in the starch matrix and served as a barrier against amylase digestion. Different levels of WPI addition had diverse effects on the oral friction characteristics and rheological properties of the composite system. As the protein addition amounts were lower than 45% (w/w), the composite gels had lower lubrication properties and elastic modulus. While as the addition levels were higher than 45% (w/w), the composite gels exhibited higher lubrication properties and elastic modulus. Texture analysis indicated that the hardness value of the composite gel increased from 0.65 N for the individual LRS gel to 4.75 N for the composite gel of LRS+100% WPI. Furthermore, it was found through low-field nuclear magnetic analysis that the addition of WPI restricted the free movement of water molecules and enhanced the water-holding capacity of the composite gels.