No abstract

-Foams represent an important area of research because of their relevance to many industrial processes. In continuous foaming operations, foaming ability depends on the process parameters and the characteristics of the raw materials used for foamed products. The effects of fluid viscosity and equilibrium surface tension on foam structure have been studied extensively. Furthermore, as surface active agents diffuse to the interface, they can modify other interface properties through their adsorption, such as interfacial rheology and surface tension kinetics. In order to better understand how these two interfacial properties influence foam structuring, we formulated model foaming solutions with different interface viscoelasticity levels and adsorption rates, but all with the same equilibrium surface tension and viscosity. The solutions were made up of a surface active agent and glucose syrup, so as to maintain a Newtonian behaviour. Five surface active agents were used: Whey Protein Isolate (WPI), sodium caseinate, saponin, cetyl phosphate and Sodium Dodecyl Sulphate (SDS), at concentrations ranging from 0.1% to 1%. Their molecular characteristics, and their interaction with the glucose syrup, made it possible to obtain a range of interface viscoelasticities and surface tension kinetics for these model solutions. The solutions were whipped in a continuously-operating industrial foaming device in order to control process parameters such as shearing and overrun, and to ensure that the experiment was representative of industrial production. The structure of the foams thus obtained foams was then determined by characterising bubble size using image analysis. For all the model solutions, both the viscoelastic moduli and apparent diffusion coefficient were linked to foam structure. The results showed that both high interface viscoelasticity and rapid diffusion kinetics induced a foam structure containing small bubbles. Both effects, as well as the impact of the shearing rate, through the rotor speed, were then integrated in a predictive model for bubble size.Résumé -Effets des propriétés interfaciales sur la structuration de mousses : étude sur produits modèles et à l'échelle pilote -Les mousses représentent un domaine de recherche important en raison de leur pertinence dans de nombreux procédés industriels. Dans l'opération de foisonnement en continu, la capacité moussante dépend des paramètres du procédé et les caractéristiques des matières premières utilisées. L'effet de la viscosité du fluide et de la tension superficielle à l'équilibre sur la structure de la mousse a été largement étudié. Cependant, lorsque les agents tensio-actifs diffusent aux interfaces, ils s'y adsorbent et modifient ainsi les autres propriétés de l'interface, en particulier la rhéologie interfaciale et la cinétique de tension superficielle. Afin de mieux comprendre comment ces propriétés interfaciales influent sur la structuration de la mousse, nous avons formulé des solutions