Oil Structuring in Dairy Fat Products
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A range of dairy products are consumed on a regular basis as sources of macronutrients (fats and proteins) and micronutrients such as minerals and fat-soluble vitamins. Among these, there are products such as butter and cheese that form a part of daily diets and then there are others such as whipped cream and ice-creams that are usually considered as indulgence products. From colloid science point of view, these products could be broadly classified as structured emulsions (butter and butter spreads), coagulated gels (various cheese types) and foamed emulsions (ice-creams and whipped creams). These products have different microstructures (Fig. 13.1), all of them containing a significant proportion of milk fat distributed either in the bulk or dispersed phases. Milk fat is composed primarily of triglycerides (TAGs) with a significantly high proportion of saturated fatty acids (Table 13.1). Palmitic acid, the main fatty acid in milk fat, is known to increase the risk of cardiovascular disease (CVD) (Wang et al., 2017). And it has been consistently suggested by health agencies that replacing dairy fats with vegetable oils rich in polyunsaturated fatty acids reduces the risk of CVD (Chen et al., 2016; Nettleton, Brouwer, Geleijnse, & Hornstra, 2017). However, the high melting fraction of milk fat (composed of TAGs rich in long-chain fatty acids) is responsible for providing the underlying colloidal network of crystalline particles, which in turn governs the macrostructure and organoleptic properties of dairy fat products. Such properties include spreadability of butter and cheese spreads, plasticity of baking butter, hardness of cooking butter, voluminous body of whipped cream, texture of cheese, creaminess of ice-cream and melt-in-mouth effect of most dairy fat products. In addition, the stabilizing effect provided by bulk crystallization of milk fat in butter and interfacial stabilization of partially coalesced fat globules in whipped cream and ice cream is also dependent on the high melting TAGs in milk fat. Due to this broad range of functionality provided by milk fat, it is a challenging prospect to replace high melting milk fat with liquid vegetable oils rich in polyunsaturated fatty acids without compromising on the product attributes of reformulated dairy fat products.
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