Food foams are dispersions of a gas in a liquid matrix. These systems can be encountered in a wide range of applications from dairy desserts to bakery products (Rodríguez et al 2008). The traditional foaming processes such as beaters or continuous rotor-stator whipping systems do not allow controlling the rate of air incorporation and are for the most part of them energetically costly. Recently, the use of microfluidic devices has arisen as a promising alternative for the manufacturing of emulsions and foams. Indeed, controlling incorporated gas fraction as well as the size of the drops and bubbles produced is easier with such devices (Laporte et al, 2016). Additionally, the residence time in the devices is remarkably smaller.

This study sets out to investigate a continuous system based on the arrangements of microchannels for a foaming application. In order to get closer to real conditions encountered in food industrial applications, a model solution formulated with biosourced molecules is used. An aqueous solution including whey proteins and xanthan gum is mixed with N2 using a cross-flow configuration to produce bubbles inside the channels. The typology of the gas-liquid disperse system is captured using a high-speed imaging equipment capable of freezing bubbles travelling at velocities in the range from 2 to 21 m·s^-1.

In order to understand the respective importance of the factors influencing the flow pattern, visualizations of the two-phase flow generated with liquid bases of different rheological behaviours are also implemented. The bubbles obtained from the studied solutions have been found to differ in size and shape as well as in their mutual arrangements, depending on the value of the Reynolds number and on the presence or not of a surfactant. Moreover, compelling bubble deformations have been observed which might contribute to breakup mechanisms of the dispersed phase inside the microchannels. Interfacial phenomena appear to be a key factor in the deformations observed.

Bibliography

Laporte, M., Montillet, A., Della Valle, D., Loisel, C., & Riaublanc, A. (2016). Characteristics of foams produced with viscous shear thinning fluids using microchannels at high throughput. Journal of Food Engineering, 173, 25–33.

Rodríguez Patino, J. M., Carrera Sánchez, C., & Rodríguez Niño, M. R. (2008). Implications of interfacial characteristics of food foaming agents in foam formulations. Advances in Colloid and Interface Science, 140(2), 95–113.