Microphotography of Raw and Processed Milk

Raw milk is a colloid, in which fat globules of various sizes are dispersed within a watery phase of dissolved proteins, carbohydrates, vitamins, electrolytes and minerals, along with low levels of probiotic bacteria such as lactobacillus. The purpose of this pilot study is to examine whole milk – raw and processed – to look for any differences in its colloidal structure that can be seen using an optical microscope. In particular, we looked for differences between unpasteurized raw whole milk compared to whole milk that is pasteurized (heated to 170 degrees F for nineteen seconds) or ultrapasteurized (heated to 280 degrees F for two seconds, using superheated metal plates and steam, and then chilled). We also looked at the effects of homogenization of milk. Milk samples were observed under the microscope over a large range of magnification and two types of illumination, bright field and dark field.