Production of whey protein isolate – gellan microbeads for encapsulation and release of flaxseed bioactive compounds

Abstract

Production of 1.5% (w/v) whey protein isolate (WPI) – 0.1, 0.3 or 0.5% (w/v) gellan gum microbeads from extrusion of the oil-in-water (O/W) emulsions into a 0.56% (w/v) calcium chloride (CaCl2) solution was evaluated to encapsulate flaxseed oil (15% v/v) and protein hydrolysate (FPH) (0, 0.25 or 0.5% w/v). Microgels resistance and controlled release of oil and FPH were also investigated. Microscopic images showed few free oil droplets and a prevailing presence of gellan on the external surface of the microbeads, indicating that oil and FPH were encapsulated. Microbeads produced at higher gellan concentrations (0.3 or 0.5% w/v) showed a more regular and spherical morphology. However a significant decrease in microbeads size (from ∼55 μm to ∼50 μm) and an increase in the polydispersity were observed with the FPH addition, which can be a consequence of the formation of a more dense biopolymers network. FPH presence (0.25% w/v) decreased the viscosity and shear thinning behavior of microbeads suspensions (10–90% w/v), which could be partly attributed to the smaller size of particles. The microbeads suspensions were stable at different salt concentrations (0.56, 1.11 or 2.22% w/v) regarding their shape, not releasing the encapsulated oil. 1.5% (w/v) WPI – 0.3% (w/v) gellan microbeads were resistant to simulated gastric conditions, but did not resist to intestinal conditions. Our results show that these microgels are adequate to encapsulate bioactive compounds to be released in the small intestine, passing intact in the stomach, which makes the process attractive in order to maintain the bioavailability and functionality of such compounds.