Beyond homogenization: the formation of very small emulsion droplets during the processing of milk by a Microfluidizer

Abstract

Comparisons were made of the particles of fat and casein produced when milk is treated with a Microfluidizer, or is homogenized by a valve homogenizer. The results show that the particles in the two milks are very different, especially if several passes through the apparatus are used. The milks treated by Microfluidizer contain smaller particles overall than the homogenized milks, but these particles also have different structures. Specifically, the membranes of protein around the fat globules are different, and in the microfluidized milks, there are fewer intact or semi-intact micelles forming the surface of the fat globule. Also, the microfluidized milk contains very small particles of fat (30-50 nm in diameter), coated with protein. These small particles can exist on their own, but often also were found to be inserted into apparently intact casein micelles. The significance of these results for the understanding of homogenized milks is discussed, with some suggestion of the mechanism of formation of the different types of particle.