The aim of this study is to understand the interactions between molecular product/process and to estimate the influencing factors (e.g. thermal treatment, ingredients and operating conditions) in order to control foam properties, i.e. the microstructure of foamed products stabilized by aggregates of whey proteins (WPI). A first study allowed us to estimate the impact of the dynamic thermal treatment on the WPI solution (amount, size and morphology of the protein aggregates), and also on the foaming ability of native or heat-treated whey proteins when a bubbling technique was used. Secondly, foams produced using a batch mixer allowed us to highlight the key role played by the soluble fraction of protein aggregates in improving the stability against drainage and the texture of protein foams without fat. On the other hand, the application of a severe post-treatment to WPI solutions was shown to be unfavourable to the stability and to the rigidity of protein foams. By using a continuous rotor-stator device and a narrow annular gap unit, we have clearly demonstrated the relationship between the process/product interactions. When a thermal treatment superior or equal to 80°C was applied before foaming on the rotor-stator, this seemed to improve significantly foam rigidity and confirmed that foam stability over time remained essentially governed by the denaturation and aggregation degrees of whey proteins, the operating conditions playing only a secondary role. On the other hand, when a narrow annular gap unit was used, this beneficial effect of heat treatment on stability against drainage and also on foam texture was hidden by process variables and no apparent improvement was observed.
STUDY OF THE PROCESS/PRODUCT RELATIONSHIP DURING THE PRODUCTION OF FOOD FOAMS STABILIZED BY WHEY PROTEIN AGGREGATES