Effet de la formulation sur l’élaboration de mousses laitières de type « topping »

The influence of gelatine substitution in a model dairy emulsion by a mixture of hydrocolloids including xanthan, carrageenan and guar (XCG) has been investigated on its foaming capacity. The model emulsions were prepared using either high pressure homogenization under 10 MPa or membrane emulsification, with either 100 nm or 500 nm pore size. Continuous foaming operation was carried out using a rotor/stator device under steady-state flows conditions. The effect of rotation speed under constant residence time and pressure has been investigated. While the emulsions have been characterized in terms of rheological parameters and fat droplet size distribution, the foams have been characterized by their overrun, bubble size distribution, texture and stability. The results have shown that the method used for the preparation of the emulsions influences strongly their properties. Conversely, the substitution of gelatine by the XCG mixture has only a minor effect on the emulsion properties, but it has been reported to affect significantly the bubble size distribution and the stability of the foams. Finally, it has been shown that when the mean diameter (d43) of the fat globules remains lower than 4.5 mu m, membrane emulsification and high pressure homogenization lead to similar overrun and mean bubble diameter values. The combined effect of the rheology of the emulsions and rotation speed during foaming has been estimated using the power curve of the rotor/stator unit. According to this curve, when foaming occurs in laminar flow, the operation is successful, which is always the case when an emulsion based on XCG has been used. Conversely, the reproducibility of foaming operation remains poor and overrun decreases generally in the transition region, which has been observed for some emulsions based on gelatine at high rotation speed.