Microstructural Observation of Dairy Products Using High-pressure Freezing in Combination with Cryo-scanning Electron Microscopy

Observation of bovine raw milk and cream was attempted by combining high-pressure freezing with cryo-scanning electron microscopy (SEM). In raw milk, casein micelles were observed to be distributed in the aqueous phase, with an average diameter of about 140 nm, which was in agreement with previous reports. In cream, the number of casein micelles adsorbed on the fat globule interface was observed to be larger compared with that observed under freeze replication with a cryoprotectant. Results showed that high-pressure freezing combined with cryo-SEM is a useful method for observing the native structures of raw milk and cream in their original states, which was difficult to achieve using conventional electron microscopy.