Membrane and membraneless osmosis

Semi-permeable membranes, such as those used in ultrafiltration, have many potential applications in the food industry. Ishikawa and Nara (1992) pointed out, however that the main problem with these systems was the permeation of the solute used in osmosis into the foodstuff. This could be controlled by the use of a semi-permeable membrane placed in intimate contact with the food, that is, with no free space between the membrane and the food. They investigated the use of a membrane made from a chitosan gel. Chitosan is prepared from chitin, a glycan separated commercially from the shells of crustaceans. Chitosan is both semi-permeable and edible. They postulated that food could, therefore, be coated with a chitosan membrane, thereby eliminating any free space. As yet, chitosan is not permitted as an additive in foods, but this technique may find wide applications in the food industry if chitosan were to be accepted as a processing aid for foodstuffs. 

An alternative to the use of synthetic, or edible membranes is membraneless osmosis. Milk protein has been concentrated by the use of this technique (Tolstoguzov, 1991). Instead of separation being achieved 

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