Note. Study of some typical Spanish cheeses by scanning electron microscopy. Main microstructural modifications caused by freezing

The microstructure of some Spanish cheeses anal the main microstructural mo difications caused by freezing are studied by scanning electron microscopy (SEM). In cured and pressed cheeses such as Manchego and Mahon cheeses, the protein matrix constitutes a compact network in which fat globules, unifor mly distributed, are immersed; frequently, these spherical globules are lim ited by an apparent protein membrane. In the protein matrix, micellar bodie s are identified in different aggregation grades; this is a characteristic of the enzymatic coagulation. In non-cured Herreno cheese (pressed paste) t he compaction grade of the casein micelles is less than in cured and presse d cheeses. In fresh cheese, which is a fresh and non-cured cheese, proteins are distributed as micelle clusters more or less loose. Large fissures and small spherical voids, which would probably contain whey, air or fat, are observed. Cottage cheese, a non-pressed paste, is obtained fundamentally fr om whey protein coagulation; the protein bodies are distributed loose or in the form of clusters, and large voids are formed. Freezing at -25 degrees C affected the pressed and cured cheeses (Manchego and Mahon) and non-cured cheeses (Herreno); the spherical voids containing fat are deformed, the pr otector membranes are broken, and reticular structures and micellar bridges are found inside the protein matrix. In non-cured and soft paste cheeses s uch as fresh cheese, the protein matrix becomes hard with fissures, and the spherical voids appear destroyed and deformed. Freezing produces total des truction of the cottage cheese structure. Texture studies of the cheeses (s hear strength) agreed with microscopy results by SEM.