Milk fat modification

Although the processes of hydrogenation and chemical interesterification that are commonly used in the wider oils and fats industry may be applied to milk fat, there are a number of factors that prevent these being an attractive option for milk fat modification. Apart from the fact that ingredient manufacturers are seeking alternatives to the use of chemicals, milk fat is... 

Mogensen, G. 1985. Technological and quality aspects in milk fat modification. In, Milk Fat and its Modification. (R. Marcuse, ed.), pp. 54-68, Proceedings LIPIDFORUM Symposium, SIK, Goteborg, 26-27 January 1984, Goteborg. 

O Donnell, J.A. (1993). Future of milk fat modification by production or processing Integration of nutrition, food science and animal science. ]. Dairy Sci. 76,1797-1801. 

Despite the biohydrogenation of unsaturated acids in rumen, the administration of direct doses of vegetable and fish oils (as feed supplements) produces larger concentrations of unsaturated FA such as C,8, C,8,2, and C,8,3 in milk fat at the cost of saturated acids. To improve the effectiveness of milk fat modification and limit the biohydrogenation, animals are fed encapsulated fats in the form of for example, full oil seeds of flax, rape, vegetable oil preparations encapsulated in casein denatured with formaldehyde, FA calcium salts, or FA amides. 

As the result of feeding cows encapsulated fat, desirable milk fat modification can be obtained so that the PEFA in fat are limited. A conjugated linoleic acid (CLA), also referred to as rumen acid cis-9, trans-11 -octadecadienoic acid), is a nutritionally important fat component. If present in the human diet, this acid prevents obesity,... 

Dried whole milk is prepared by conventional spray or roller drying, with some modifications of the preheat treatment of the milk. The product is usually stored under nitrogen to delay lipid oxidation and off-flavor development. In spite of the processing changes, flavor defects and short storage life have limited the markets for dried whole milk most of it is used in the confectionery and baking industries. Federal and FAO standards require a minimum of 20% but less than 40% milk fat and a maximum of 5% moisture. 

As always in the analysis of milk fat, the short chain fatty acids cause problems. A major difficulty has not been the GLC separation of these acids but their transfer from the esterification mixture to the GLC instrument without loss of the volatile esters. A widely used procedure is a slight modification of the method developed by Chris-topherson and Glass (1969) which uses sodium methoxide for transesterification. This technique can be employed with other fats, but not with those containing appreciable amounts of free fatty acids where HCl-methanol is required. 

Caponio, F., Allogio, V. and Pallavicini, C. (1998) Modification of goat milk fat triglycerides by immobilised lipase. Fett Lipid, 100, 74-78. 

Milk fat is valued for its pleasant flavor but its melting and rheological properties often need to be modified to make it more suitable for many food applications. The uses of milk fat can be increased by the application of various processing interventions such as fractionation, selective blending and texturization, and chemical or enzymic processes to produce speciality milk fat ingredients (Kaylegian, 1999). Most of these modification procedures... 

This chapter is focussed on the post-farm modification of milk fat by physical, chemical or enzymic means. The use and control of these processes for differentiation of milk fat to widen its application range or tailor it for specific end-applications (Mortensen, 1983 Mogensen, 1985 Boudreau and Arul, 1991 Rajah and Burgess, 1991) will be discussed. The effects of the modification processes and minor lipid components on the texture and crystallization behavior of milk fat are covered. The potential for applying modification processes to improve the nutritional quality of milk fat is also considered. 

Physical modification of milk fat by fractionating milk fat or by blending milk fat or milk fat fractions with other oils and fats results in products with an altered triacylglycerol composition, but one in which the fatty acids in milk fat maintain their original position in the triacylglycerol molecules (Kaylegian, 1999). 

Modification of Milk Fat Properties by Addition of Minor Lipids... 

Minor lipids can have a significant influence on the kinetics of crystallization of milk fat. The effects on the kinetics of crystallization processes should be separated from their influence on the final properties of the milk fat. The effects of minor lipids on the modification of milk fat properties are complex and are dependent on the type, chemical nature, concentration and structure of the minor lipids (Wright and Marangoni, 2002a Vanhoutte et al., 2002a). 

Milk fat may be chemically modified to obtain products with altered functionality. In contrast to physical modification of milk fat where the position and nature of the fatty acid chains of the triacylglycerols are maintained, the use of chemical processes results in modification of the composition of the fatty acid chains or their positions in the triacylglycerol molecule. 

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