Microstructural properties of milk fat globules

A method is presented to quantitatively measure structural changes induced by milk processing and storage, such as fat aggregation and milk fat globule membrane disruption, by analysing confocal micrographs. Ultra high temperature treated, microfiltered, homogenised high-pasteurised, homogenised pasteurised, and unhomogenised pasteurised milks were purchased; raw milk was from a local dairy farm. Three samples of each milk type were stained for milk fat phase with Nile Red for confocal observation and 10 images were acquired for each sample. Images were binarised and analysed by using both an algorithm measuring 8 features related to geometrical properties of fat globules and a trained panel (6 people). Principal component analysis validated that quantitative measurements on confocal micrographs can recognize structural differences. Milk treatment significantly affected (P < 0.0001) fat globule size, aggregation and fusion. Storage temperature had a lower impact on the differences among the samples, inducing changes just in some of them.