Food Structure


B. E. Brooker


The role of fat crystals in the stabilisation of air bubbles in cake batters was studied with aqueous phase aerations prepared by the "all in one" method using shortening containing emulsifier. During mixing, fat crystals become coated with an interfacial layer of ad sorbed protein (crystal -water interface). They adsorb to the surface of bubbles (that have been transiently stabilised by egg proteins) by a process which involves the fu sion of the crystal-water interface with the air-water interface.

The adsorption of fa t crystals helps to stabilise large numbers of small bubbles which must expand without rupturing during baking if the batter is not to col lapse. During heating, the fat crystals melt, the oil runs over the internal surface of the bubble and leaves behind the crystal-water interface which can be used by the bubble to provide extra interface during its expansion. Implicit in this mechanism is the explanation for: a) how fat moves from the aqueous phase to the inside surface of air bubbles during coo king ; b) why oil does not produce the same degree of cake aeration as the same weight of crystalline fat; and c) the fact that shortenings containing crystals of the B-polymorph perform better than those containing the larger B-polymorph.

A similar mechanism may operate in other aerated cereal products, such as bread, in which crystalline fat is known to produce similar improvements in volume and crumb structure.

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