Effect of surfactant sucrose ester on physical properties of dairy whipped emulsions in relation to those of O/W interfacial layers.

Dairy foams were manufactured on a pilot plant with various sucrose ester contents. Oil-in-water emulsions were produced by high-pressure homogenisation of anhydrous milk fat (20 wt%) with an aqueous phase containing skim milk powder (6.5 wt%), sucrose (15 wt%), hydrocolloids (2 wt%), and sucrose esters. Sucrose ester content was varied from 0 to 0.35 wt%. Firmness and stability of dairy foams were determined. The fraction of protein associated with emulsion fat droplets and the compression isotherms of those droplets were determined as a function of sucrose ester content. With less than 0.1 wt% sucrose ester, no foam could be produced. The most firm and stable foams were obtained with ca. 0.1 wt% sucrose ester. The fraction of protein associated with emulsion droplets suddenly falls from 60% at a sucrose ester content lower than 0.1125% down to ca. 10-20% for higher surfactant content. Compression isotherms of emulsion droplets at the air-water interface show that, in the presence of surfactant, emulsion droplets disrupt and spread at the interface whilst without surfactant they become dispersed. This means that the presence of sucrose ester causes some destabilisation of fat droplet interfacial layers. There is hence an optimal sucrose ester content that allows some destabilisation of the oil-water interface without concomitant protein displacement from that interface. Consequently, with the recipe and manufacturing process used to produce dairy foams, there exists a compromise in sucrose ester content with regards to manufacture and shelf-life of dairy foams.