Fracture and textural properties of low fat egg yolk gels containing emulsion droplets

The influence of corn oil content and the type of emulsifier on the fracture and textural properties and the expressible liquid of gels prepared by heat-treatment of low-fat yolk protein concentrate (YPC) containing emulsified oil has been investigated. Oil incorporation in the form of fine droplets results in a decrease of gel network strength, the textural parameter values depending on the amount of added oil. Tween 20 (polyoxyethylene sorbitan monolaurate) when used as the oil emulsifier brings about a reduction in gel textural parameter values compared to liquid egg yolk, the result depending on the emulsion droplet size. Additionally, the gels differ in their yielding behaviour since the latter yield but do not fracture at strain values as high as 0.7 while the former fracture at relatively low strains and their fracture stress and strain parameter values depend on oil droplet size. This behaviour is explained in terms of the effect of the surfactant on the yolk constituents and, particularly, its interactions with the yolk apoproteins, which result in stiffer bulk gel network structure.