Food Structure


Interfacial changes occurring during the formation of whipped cream were followed using transmission and scanning electron microscopy. During the initial stages of whipping, air bubbles were stabilized by adsorbed 8-casein and whey proteins with little involvement of fat globules. The adsorption of fat to a i r bubbles occurred ~.then the globule membrane coalesced with the protein a ir-water i nterface . As a res ult, fat was brought into direct contact with air but only rarely did it spread at the ai.r-fat interface. The crosslinking of fat globules adsor bed t o adjacent air bubbles by chains of coalesced globules established a stabilizing infrastructure in the foam. In t he final whipped cream , the surface of each bubble was stabilized by variable amounts o f adsorbed fat and by the o riginal air-water interface of adsorbed proteins . Although these remnants of protein do not cont r ibute to the mechanical proper ties of the foam, they betray the mechani.sm of bubble stabilization. A similar foam structure was also found in dairy and non-dai r y aerosols exami ned by freeze fracturi ng. Modifying the protein composition of the aqueous phase before whipping may have important effects on the final foam because of the way this affects the composition of the air-water interface and , subsequently, the ease of fat adsorption to air bubbles .

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