Rheological characterization of melting of margarines and tablespreads

Abstract

Margarines and tablespreads are water-in-oil emulsions. Melting characteristics of these products are important for flavor release and consumer acceptance. Oscillatory measurements as a function of temperature, and also drop points, were used to quantify rheological changes accompanying melting. DSC measurements were used to quantify melting of fat crystals in these products. For low-fat spreads it was found that rheological changes characteristic of melting could occur at a temperature higher than when fat melting occurs and that the fat melting is largely unaffected by emulsification. The rheology of low-fat spreads is governed by emulsion characteristics such as the proportion of the aqueous phase and the size of the water droplets. Drop point measurements provide a simple method to determine melting in the rheological sense. Perceived meltability of these products, in general, represents a combined perception of cooling sensation accompanying the melting of fat crystals and the sensation of flow accompanying the rheological transitions. The cooling sensation is significant only for the case of butter and high-fat margarines. In these cases the fat melting and rheological transitions both occur at about the body temperature. In reduced fat products, the cooling sensation is not significant and perceived meltability correlates with the viscoelastic and drop point data.