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Food Structure

Authors

B. E. Brooker

Abstract

Foods containing aqueous solutions of proteins readily foam when air is introduced into them. When fat is also present, interaction between the two components at the air/water interface may produce a stable foam with characteristic bulk properties. In the case of dairy foams (such as whipped cream), bubbles produced in the whipping process are initially stabilised by the adsorption of protein at the air/water interfaces.

Commonly encountered defects in whipping cream arise when large triglyceride crystals, formed in masses of free fat, adsorb to the air/water interface during whipping at the expense of fat globules.

In other food systems , fat crystal adsorption is part of the normal stabilizing mechanism. In cake batters produced by 'creaming' with shortening, air is held in the fat phase and stabilised by .B'-gystals; however, bubbles move into the aqueous phase during cooking. Studies with batters in which the air is in the aqueous phase have shown the importance of both protein and .B' -crystals in air stabilisation. The added importance of fat crystals is that they provide extra protein air/water interface for the bubbles as they expand during cooking and, thereby, help to preserve the texture of the final product.

The fat protein interactions observed at the air/ water interface of several different foams, provide a unifying mechanism for the stabilisation of air in many diverse food systems.

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