Impact de la cristallisation des corps gras sur les propriétés des produits finis

In various food products, the fat phase which is almost essentially composed of triacylglycerols is found in a crystallized form at temperature of use or of storage. The fat physical characteristics influence the rheological properties and the stability of the products. In food, the fat phase is frequently found in a dispersed form either as oil in water emulsions (ice cream, whipped topping) or as water in oil emulsion (butter, margarine). The mechanism of fat crystallisation is different in the bulk phase and in emulsified systems so that the fat behaviour in emulsion can not simply be deduced from that in the bulk phase. In particular, crystallization in emulsion depends on various parameters such as the fat globule size and the presence of surfactants (proteins and low molecular weight emulsifiers). Moreover, fat crystals play a major role in the emulsion stability, i.e., by stabilizing water in oil emulsions and destabilizing oil in water emulsions. Conversely, crystals are implied in the formation of a fat network of partially coalesced droplets that participates to the foam stabilization in aerated food products based on oil in water emulsions