Destabilization of aerated food products: effects of Ostwald ripening and gas diffusion

In this paper, we study two processes by which aerated food products are destabilized, namely, Ostwald ripening and gas diffusion to the atmosphere. The result of these processes is a change in the size distribution of bubbles as well as a decrease in the volume of air that is retained in the system, with time. The driving forces for these processes is the capillary pressure difference between bubbles of different sizes (for 0stwald ripening) and just the capillary pressure in a bubble (for diffusion to the atmosphere). A theoretical model is developed to describe the effect of these two processes on the bubble size distribution and volume fraction of air for foam systems (overrun of ca. 1000%). The predictions are compared with experimental results for two aerated food systems generated using two different emulsifiers, namely triglycerol stearate and propylene glycol stearate. The stability of the aerated food products could be predicted based on the model parameters derived from measurements of gas diffusion from a single bubble. In both the experimental systems, it was found that Ostwald ripening decreased the rate of gas loss from the system as a whole, by increasing the bubble size and hence decreasing the capillary pressure of the bubbles in the system. (C) 2003 Elsevier Ltd. All rights reserved.