MICROSTRUCTURE OF MOZZARELLA CHEESE DURING MANUFACTURE

Scanning electron microscopy was used to examine structural developments during the manufacture of low-moisture, part-skim Mozzarella cheese made by a stirred curd procedure. The micrographs showed changes in the protein matrix, dispersion of fat globules, and bacteria during processing. Most curd knitting occurred during the curd stirring step, particularly dry stirring. A thin (5 mum) curd skin was observed on curd particles at the end of dry stirring. Dry salting prior to stretching resulted in the rapid loss of whey from the curd particle. Protein fibers were aligned and longitudinal columns of whey and fat were formed when the cheese was stretched and molded. Bacteria were initially dispersed throughout the protein matrix, but after stretching, most of the bacteria were located at the fat-whey/protein interface. Brining cooled the cheese causing the fat globules to solidify and additional whey to be expelled, resulting in fat globule indentations in the protein matrix. These micrographs can be used to monitor changes in curd structure when Mozzarella manufacturing procedures are modified. An understanding of the protein/fat interactions and curd structure development during manufacture will help optimize the physical properties of reduced-fat, low-fat, and non-fat Mozzarella cheese.