Heat stability and emulsifying ability of whole egg and egg yolk as related to heat treatment

Egg proteins are extensively utilised in many food products due to their unique functional properties. Some of the egg proteins are particularly sensitive to heat treatment and that can be a limitation to the processing of egg containing products. Suspensions of whole egg and egg yolk were heated at various temperatures in the presence of variable concentrations of sugar and salt. It was shown that egg proteins can withstand severe heat treatments when sugar and salt are present during the process. Depending on the sugar and salt concentrations, whole egg and egg yolk suspensions can be heated at temperatures as high as 80°C (2 min). Sugar and to a higher extent salt had an impact in delaying the denaturation of egg proteins and thus, increased heat stability. The effects of this heat treatment on the emulsifying properties of egg proteins were investigated for a range of protein content levels. Our results indicate that despite the severe heat treatment the egg proteins heated in the presence of sugar and salt were still capable of forming and stabilising emulsions. The sugar and salt concentrations present during the heating process, under specific temperature-time conditions, are correlated with the ionic strength of the solution and the degree of denaturation of the egg proteins, which in turn determine the adsorption capacities of the latter to the interfacial film.