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'' encapsul ation of fluid milk samples in their prefixation preparation for elect ron microscopy. The new technique is based on making cubic wells in an agar gel layer, filling them with fluid milk samples, and sealing the m 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 fix ed, dehydrated, and embedded in a resin for transmission electron micr oscopy. The procedure is simpler, and more versatile, reliable, and re producible than other encapsulation methods used to prepare similar fo od samples. Agar gel tubes used in the other methods have several disa dvantages such as the need for manual dexterity of the experimenter to make them, and difficulty in sealing the filled capsules properly. Re sults obtained by the microcube procedure were compared with results o btained 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 a gar encapsulation but shows agar strands in the micrographs of the mil k samples, which is particularly undesirable when investigating, for e xample, intermicellar strands of gelled UHT (ultra-high temperature-tr eated) milk concentrates. Microcube encapsulation produces superior qu ality images of the fluid food structure.