Plant-dairy protein blends: gelation behaviour in a filled particle matrix

Abstract

• All emulsion droplets showed extensive bridging flocculation. • Viscosity of the emulsions varied depending on the type of protein added. • During heating, structure formation of the mixed systems showed three different stages. • Lupin or pea protein isolates with whey protein caused an earlier onset of aggregation. The objective of this work was to study the structure formation in mixed protein systems containing oil droplets. A model system was prepared with skim milk, whey proteins and plant proteins to a final concentration of 8% (w/w) and homogenized with 20% (w/w) coconut fat. Three plant-derived protein sources (namely, pea isolate, oat concentrate, and lupin isolate) were added to skim milk at two different ratios of plant/dairy proteins. A blend containing only dairy protein was also used as reference, prepared with skim milk and whey protein isolate. The formation of structure in the emulsion filled gels after homogenization and heating were evaluated, using SDS-PAGE, light scattering, rheology and confocal microscopy. All emulsions showed a high viscosity due to the high extent of bridging flocculation amongst the oil droplets confirmed by a decrease in the particle size of emulsions upon the addition of SDS. After heating and cooling, the emulsions showed no macroscopic phase separation. The results demonstrated that structuring of complex gels can be modulated by controlling the composition at the oil-water interface, as well as by modulating processing conditions, capitalizing on the gelling properties of the single components in the matrix.