Interfacial interaction during the foaming of nonhomogenized cream

The aim of this study was to characterize the interfacial interactions taki ng place during the whipping of non homogenized cream. For this purpose fat crystallization was influenced by means of a cold-warm-cold treatment and the protein phase of the cream was modified. A cold-warm-cold treatment cau ses the whipping time as well as the drainage to decrease. Soluble whey pro tein leads to a longer whipping time. If denatured, microparticulated whey protein is added, the whipping time remains short. The same applies when ca sein concentrate is added to cream with a low protein content. In the whipping process first air is introduced into the system and a surfa ce between air bubbles and serum is created (Phase 1), which is covered imm ediately by beta-casein and whey proteins (Phase 2). Afterwards, an exchang e of proteins against fat globules takes place on the air surface (Phase 3) , depending on the kind of present proteins. Thus native, non-aggregated wh ey proteins disturb the exchange on the surface because in this case they a re able to form a rigid layer around the air bubbles. The adsorption of cas ein instead of whey protein first supports the inclusion of air as well as the dispersion of air bubbles. Secondly, this unstable protein layer can ea sier be replaced by the fat globules, which is essential for a stabile whip ped cream structure. Fat crystals that protrude out of the fat globules sup port this mechanism. The stabilization of the cream foam is realized by fat crystal bridges between fat globules that are adsorbed on the surface (Pha se 4).