Morphology, surface characteristics and tribological properties of whey protein/chitosan composite particles and their fat replacing effect in O/W emulsion

Abstract

Whey protein isolate (WPI) and chitosan were used to fabricate WPI/chitosan composite particles at temperatures of 75 °C (WPI/chitosan-75) and 95 °C (WPI/chitosan-95). The morphologic structure, surface properties, and the resulting tribological characteristics of the particles were investigated. The composite particles showed larger particle size than pure WPI particles (WPI-75) (~ 509 nm), with WPI/chitosan-95 the largest (932 nm). WPI/chitosan-75 showed complete core-shell structure from microstructure results. The dispersion of WPI/chitosan-75 exhibited higher surface hydrophobicity but lower viscosity compared to WPI/chitosan-95. Tribological analysis revealed that WPI/chitosan composite particles showed dramatically lower friction coefficient (μ) than pure WPI particles at sliding speed <10 mm/s and WPI/chitosan-75 demonstrated superior lubrication effects. With the presence of artificial saliva, the μ of WPI-75 was greatly lowered at sliding speed <16 mm/s, while the values of WPI/chitosan-75 only showed a slight decrease at sliding speed <1 mm/s. Chitosan might have played the similar role as artificial saliva in lubricating on the hydrophobic surface. Moreover, the incorporation of 0.5 % WPI/chitosan-75 in the low-fat (5 %) oil-in-water emulsion led to even lower μ than full-fat (20 %) emulsion at sliding speed <10 mm/s. Hence, WPI/chitosan-75 exhibited promising potential as a fat replacement and biolubricant.