An Apparatus for a New Microcube Encapsulation of Fluid Milk in Preparation for Transmission Electron Microscopy

A simple apparatus has been developed for a new "microcube" encapsulation of fluid milk samples in their prefixation preparation for electron microscopy. The new technique is based on making cubic wells in an agar gel layer, filling them with fluid milk samples, and sealing them with another agar gel layer . The individual wells are then separated by cutting from the initial block, providing 0.5 mm walls around the samples. The embedded material (milk, buttermilk, yogurt, etc.) is fixed, dehydrated , and embedded in a resin for transmission electron microscopy. The procedure is simpler, and more versatile, reliable, and reproducible than other encapsulation methods used to prepare similar food samples. Agar gel tubes used in the other methods have several disadvantages such as the need for manual dexterity of the experimenter to make them, and difficulty in seal ing the filled capsules properly. Results obtained by the microcube procedure were compared with results obtained by two methods using agar gel tubes and also by mixing a warm agar sol with fluid food samples. This latter method is simpler than agar encapsulation but shows agar strands in the micrographs of the milk samples, which is particularly undesirable when investigating, for example , intermicellar strands of gelled UHT (ultra-high temperature-treated) milk concentrates. Microcube encapsulation produces superior quality images of the fluid