The effect of high velocity steam injection on the colloidal stability of concentrated emulsions for the manufacture of infant formulations

Abstract

A major challenge for the infant formula industry is to develop more energy efficient processes while maintaining product quality and robust manufacturing practices. An effective way of improving energy utilisation is to reduce the number of processing steps during manufacture. This study examines a novel high solids process with reduced processing steps paying particular attention to emulsion stability. Model infant formulations (whey to casein ratio, 60:40) were homogenised at a solids content of 60% w/w using an in-line colloid-mill type mixer, yielding a stable emulsion with a fat globule size distribution (D(v,0.9)) of 2.99 colonm. These formulations were heat-treated using a high velocity direct steam injection device, whereby steam is accelerated using a De Laval nozzle before injection. The steam condenses on contact with the formulation, giving up latent heat, thus heating the mix. The process was found to increase the colloidal stability of the formulations, as measured in an analytical centrifuge. The fat globule size distribution was significantly (p < 0.05) decreased to 2.69 μm after processing by the injector with a concomitant significant (p < 0.05) increase in emulsion viscosity. In conclusion, in-line homogenisation followed by high velocity steam injection, using a De Laval geometry, was successfully used for heat treatment of a high solids infant formulation.