Gliadin-based nanoparticles: Stabilization by post-production polysaccharide coating

Introduction: There is great interest in converting gluten, a by-product from wheat starch isolation, into a value added functional food ingredient. Earlier, gliadin nanoparticles were produced using liquid antisolvent precipitation, but they did not prove to be very stable in conditions relevant to food products. Materials and methods: Gliadin nanoparticles were produced by antisolvent precipitation: a gliadin in ethanol solution was titrated into water. After production, the nanoparticles (0.5 w/v% protein) were coated with different polysaccharides: octenyl succinic anhydride (OSA) starch; low methoxyl pectin (LMP); or, high methoxyl pectin (HMP). Results and discussion: At all concentrations used (0.001 - 0.20 w/v%), OSA- starch led to particle flocculation and precipitation, whereas both LMP and HMP were able to coat the particles without inducing flocculation at certain levels (0.10 w/v%). The mean particle size of pectin-coated particles was about double that of uncoated ones, and the charge reversed from positive (uncoated) to negative (coated) under mildly acidic conditions. The pectin coating was shown to improve the stability of the gliadin nanoparticles to environmental stresses, such as pH, ionic strength, and thermal treatment. Conclusions: Coating gliadin nanoparticles with pectin may therefore be a useful means of forming stable functional ingredients for use in the food industry, e.g., as texture modifiers, lightening agents, or delivery systems. (C) 2014 Elsevier Ltd. All rights reserved.