Physical properties, fats hardness

Accurate determination of the amount of solid fat in edible fats and oils is an essential requirement for process control in food industry during hydrogenation, interesterification and blending. Moreover, important physical properties, such as hardness, heat resistance, mouth-feel and flavor release, can be predicted via measurements of solid fat content at different temperatures using low resolution (low-field) NMR. 

Confectionery-Liquors and Liqueur. In chocolate confectionery and for pastry creams, it is the physical properties linked to the fusion and the crystallization of the fat that are essential. For milk chocolate, for coating or in bars, AMF can be used in proportions that depend on its compatibility with cocoa butter, whose properties of hardness and rapid fusion at 35°C cannot be altered. Thus it is currently accepted that AMF with high fusion levels obtained by the fractionation technique can be used. In general, milkfat has an interesting characteristic it inhibits the appearance of fat bloom (133). 

Fat fractionation as we know it today has its origins in the late nineteenth century with the invention of margarine in 1869. The secret was the careful crystallization of freshly rendered edible tallow at temperatures between 25°C and 30°C [2]. The resultant grainy mass was then hydraulically pressed to obtain a crude 60 40 separation of a soft fraction (olein) and a hard fraction (stearin). This has remained the basic principle of the modern process. The softer fraction had physical properties similar to those of anhydrous milkfat (AMF) and was easily rendered into a plastic product that could be used in place of butter. 

Rousseau et al. (1996a, b) examined the properties of physical blends and those of blends obtained on chemical esterification of milk fat-canola oil blends (using 0.5% methoxide, 78-82°C for 15-120 min). For milk fat-canola oil blends containing >20%, w/w, canola oil, chemical interesterification reduced the solid fat content of all blends (Rousseau et al., 1996a). For non-interesterilied and interesterified blends, hardness decreased with increasing content of canola oil. 

The dispersion of the crystalline fat phase in a material determines the physical and textural properties of a lipid-based product. For example, the hardness, snap, and glossy appearance of chocolate is caused by crystallization of cocoa butter in the form of numerous, very small (1 pm or less) crystals of the most stable polymorph (p form). The size distribution (mean size and range of sizes), polymorphic form, and shape of the fat crystals, as well as the network formed among the crystals, all play important roles in determining physical attributes of lipid-based products. 

Texture has been defined as the way in which various constituents and structural elements are arranged and combined into a micro- and macrostructure and this structure is externally manifested in terms of flow and deformation [1], The structural elements of fats consist of solid fat crystals. They are suspended in liquid oil and when present in sufficient quantity form a three-dimensional network that imparts plastic properties to the fat. The external manifestations of this network structure include a number of physical and mechanical properties such as hardness, softness, spreadability, brittleness, shortening power, and aeration properties. 

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