<p>The formation and stability of aerosol whipped cream, as an example of an instant foam, were studied from a physical point of view. Instant foam production out of an aerosol can is based on the principle that a soluble gas (laughing gas) is dissolved under elevated pressure (5-10 bar) in the product (cream). By opening the nozzle of the can the product is allowed to leave the can. The resulting decrease in pressure causes the gas to come out of the cream and a foam is formed.<p>Formation of the foam occurs in the smallest opening of the nozzle. Here, the velocity is limited to the speed of sound in the foam, which indicates that the flow through the nozzle is controlled by choking conditions. These conditions determine apart from the velocity also the density and pressure of the aerated cream in the nozzle. The whole process of instant foam formation is therefore regulated by the physics of choking.<p>Aerosol whipped cream is characterised by a high overrun (400-600%) which provides firmness to the close-packed foam. The overrun is determined by the amount of laughing gas (nitrous oxide) dissolved in the cream. Since the pressure in an aerosol can knows practical limits, a high solubility of the gas in the cream is required to ensure that a sufficient amount of gas is dissolved. However, this high solubility enhances the process of disproportionation. Disproportionation involves gas diffusion from smaller to larger bubbles and out of the foam, which negatively affects the foam stability. Cream showed not to have the surface rheological properties that are required to stop this destabilisation process. This explains the fast deterioration of the product. Obviously, optimising the foam properties of aerosol whipped cream involves several compromises.
|Qualification||Doctor of Philosophy|
|Award date||11 Jun 1997|
|Place of Publication||S.l.|
|Publication status||Published - 1997|