Rheological properties of food foams produced by SMX static mixers

Abstract

The objective of this work is to produce food foams in a continuous process while maintaining the required end-use properties of the foams such as stability and adequate texture.Foams are elaborated from liquid bases formulated with 3 wt% whey protein isolates as surfactant and xanthan gum (0.35–0.6 wt %) as thickener. A previous work with SMX™ 10 static mixer (Sulzer™) managed to produce foams with air fractions in the range [0.85–0.94], but the target range of the air fraction in food products is [0.5–0.8].This work aims at reducing bubbles size in the matrix in order to develop the interface and therefore to consolidate the structure. A static mixer of smaller size, the SMX+™ 6, is then used to increase the shear rate, and is compared to the SMX™ 10. The effect of the viscosity of the matrix is also investigated by using different formulations. The air fractions obtained are between 0.72 and 0.84, which is more relevant for food applications. The rheological analyses of foams are carried out by flow curves and viscoelasticity in the linear domain.It is shown that the foam shear viscosity ranks in the same order as the liquid base one, and that the yield stress and elastic modulus are in fair agreement with models of the literature.