A simplified method for examination of microstructure of mozzarella cheeses with scanning electron microscopy

Abstract

The microstructure of mozzarella cheeses was studied using a simplified method of specimen preparation for imaging. Mozzarella cheeses were prepared each with and without exopolysaccharide-producing Streptococcus thermophilus and Lactobacillus delbruckeii ssp. bulgaricus. Samples were obtained from the cheeses to study their microstructure. Specimens were cut from the cheese samples, fixed in 2% glutaraldehyde, dehydrated and impregnated using 1.5% osmium tetroxide. The specimens were dried in a critical point drying apparatus, fractured at room temperature (∼20°C), sputter coated with gold, and images of the cheese specimens taken using a scanning electron microscope. The images showed clear internal structures of the specimens. The compact protein structure of cheeses interspersed with small and large voids representing locations of the fat and serum phases, respectively, was seen. The exopolysaccharide produced by the streptococci appeared to be delicate and filamentous. The lactobacilli seemed to produce the exopolysaccharide in meagre amounts. The micro-organisms were found in serum channels.