SURFACE-STRUCTURE OF COTTAGE CHEESE CURD BY ELECTRON-MICROSCOPY

A current hypothesis is that a relatively impervious skin forms around curd particles of cottage cheese during healing and cooking. Comparisons were by both scanning and transmission electron microscopy of the surface and internal structures of small curd cottage cheese made commercially by the culture set method and on a laboratory scale by the direct acid set method. The photographic evidence, which is consistent with hundreds of visual scanning electron microscopy and transmission electron microscopy examinations, does not support the conclusion that a skin or similar impervious film forms around cottage cheese curd particles when conventional manufacturing procedures are used. However, an extreme heat treatment (1 h at 70 C) formed a surface skin. When typical cooking treatments are used, firming of the curd during healing and cooking is not attributable to formation of a skin at the curd surface. In modeling mass transport processes within cottage cheese curd, the curd should be treated as a uniform porous mass, not a particle surrounded by a relatively impervious skin. © 1979, American Dairy Science Association. All rights reserved.