Rheological characterisation of dairy emulsions for cold foam applications

Dairy foams are complex aerated materials where the liquid matrix is an emulsion made by oil droplets dispersed in a water system. An innovative application of these systems leads to an interesting product derived from instant whipped creams but stored and consumed at low temperatures (typically between -4 and -18°C) like an ice cream. This novel product requires a specific texture due to the particular conditions related to its consumptions. In the present work the effects of some relevant ingredients (emulsifiers, sugars and fats) on rheological properties and freezing temperature of dairy emulsions were investigated. Samples were prepared on lab scale and it was found that structure extension is affected strongly by stabilizers (carrageenan and guar gum) and in a lower measure by fat content. As far as freezing point is concerned a significant effect only of sugars (type and amount) and fats was measured. A formulation having interesting properties for low temperature applications was obtained and it was prepared on a pilot plant scale to investigate the potential effects of the industrial production. These samples exhibited a relevant reduction in both viscosity and elasticity; it was speculated that this effect could be attributed to the whey protein thermal damage (induced by the UHT treatment) and to the homogenization conditions, different from those adopted on lab scale.