Properties of microparticles from a whey protein isolate/alginate emulsion gel.

Designing soft, palatable and nutritious texture-modified foods for the elderly is a challenge for food technologists. The aim of this work was to produce and characterize emulsion-gelled microparticles (EGM) made from whey protein isolate (WPI) and sodium alginate (NaAlg) that may be used to modify the rheology of liquid foods and as carriers of lipids and lipophilic nutrients and bioactives. Olive oil microdroplets became embedded in the WPI/NaAlg gel matrix in the form of an emulsion produced by ultrasound (US) or high-speed blending (HSB). Oil microdroplets were obtained by US and HSB, with an average equivalent diameter varying between 2.0-3.2 µm and 4.5-6.7 µm, respectively. Oil incorporation increased compression stress of bulk emulsion gels at small deformations compared to the no-oil microgel, but this effect was reversed at high strains. EGM were prepared by shear-induced size reduction. Rheological tests at 20 ℃ and 40 ℃ showed that US-EGM and HSB-EGM exhibited a predominant elastic behavior, with G' >  G″ throughout the frequency range. However, when HSB-EGM were heated at 60 ℃ their rheological behavior changed to a more fluid-like condition, but not that of US-EGM. Consequently, EGM have the properties needed to improve food texture for people with masticatory/swallowing dysfunctions or needing special nutrition.