Effect of chitosan size on destabilization of oil/water emulsions stabilized by whey protein

Abstract

High amounts of effluent with emulsified lipids are produced during dairy process due to the presence of proteins and others surface active compounds. The aim of this work was to understand the effect of chitosan size and charge density on the de-stabilization of dairy emulsions. Emulsion were composed by water, whey protein (WPI) and sunflower and added of chitosan or chitosan oligomers at different concentrations (0.66%, 0.35% and 0.1% w/v). At the emulsion pH (7.0), oligomers were more densely charged ( + 13.80 mV) than chitosan ( + 8.59 mV) which increased their electrostatic attraction to the negatively charged proteins present at the emulsion interface. The complexation was favored by the smaller oligomer size as compared to chitosan, therefore the emulsions added of oligomers showed intense phase separation. The confocal and optical microscopy showed a gel like structure formed by oligomer-protein complexes that surrounded the flocculated droplets in emulsions. Due to the more intense interactions of oligomers at the interface, emulsions containing oligomers presented higher G’ and apparent viscosity values than emulsions added of chitosan. The greater oligomer complexation to WPI retained more protein at the emulsion upper phase and reduced the chemical oxygen demand of the remained aqueous phase. These results indicate that is possible to potentialize the use of chitosan as de-emulsifier by the reduction of its size and increase of charge density.