PROPERTIES OF SOME EDIBLE CARBOHYDRATE POLYMER-COATINGS FOR POTENTIAL USE IN OSMOTIC DEHYDRATION

A limited number of carbohydrate polymer coating compositions were evaluated for their potential usefulness for improving the osmotic dehydration of foods. A parameter P(r), or 'performance ratio', defined as (water out)/(solute in) (wt/wt). was found to be a valuable index for comparing literature results of quality judgements of coated and non-coated, osmotically dehydrated foods. Use of a model system with a diffusion cell to obtain P(r) values partially eliminated the need for conducting large-scale experiments with each food. osmotic agent and coating. Three osmotic agents (69% sucrose. 96% glycerol. 51.6% dextrose) were tested in combination with ten calcium crosslinked polysaccharide ionotropic gel coatings and two coatings produced by evaporation of ethyl cellulose in ethanol. When glycerol was used as an osmotic agent. the highest P(r) values were obtained with an ethyl cellulose coating. When a calcium ion crosslinked polymer coating was used, the greatest P(r) values were obtained with 69% sucrose as the osmotic agent and aqueous 3% low-methoxyl pectin solution in the coating.