Texture-structure relationships in foamed dairy emulsions

Abstract

Favorable textural qualities of foamed dairy emulsions result from the successful incorporation of air bubbles surrounded by partially coalesced fat globules into a stable product. Stabilizers, usually hydrocolloids, are often added to improve texture by controlling such factors as, in ice cream, the agglomeration of ice crystals and, in whipped cream, protection of the product against excessive drainage during storage. The mechanism of stabilizer action is not yet fully known and a clearer understanding of their role is needed to improve functionality and extend shelf life. This review focuses on recent work employing microstructural and rheological techniques aimed at achieving a better appreciation of the role of stabilizers in foamed dairy emulsions. Results from studies of ice cream and model systems have led to the conclusion that the growth of ice crystals in this product is governed by the kinetic properties of the freeze-concentrated viscoelastic liquid surrounding them and hydrocolloid stabilizers are effective due to their ability to increase viscosity of this liquid, possibly through the interaction of their chains. In whipped cream, preliminary data suggest that structure formation is a result of coated air bubbles surrounded by a viscous matrix of partially coalesced fat globules, perhaps held in place by proteins. Stabilizers increase viscosity of the serum phase leading to lower overrun but greater resistance of the product to drainage.