The functional, physical and morphological properties of edible fatty acid and methyl cellulose based barriers

This research addressed the fundamental relationship between the functional, physical and morphological properties of edible barriers. Food and polymer science were integrated to determine and develop the required edible barrier for a mixture of raisins with a cereal and to correlate the functional water vapor properties to the physical state and the morphology within edible barriers.; The critical moisture diffusivity through raisins and the water vapor permeance through 27 cast edible barriers composed of an emulsion of methyl cellulose as the continuous phase and a fatty acid (C:10 to C:22) as the dispersed phase was determined. Barrier physical state was determined by Differential Thermal Analysis (DTA). Barrier morphology was quantified via coupled Epifluorescent Microscopy (EFM) and Digitized Image Analysis (DIA). Mathematical models were adapted from heat transfer theory using the diffusion and solubility coefficients of water vapor within the dispersed and continuous phases.; The barrier containing 34.8% stearic acid exhibited the lowest permeance (0.26gm{dollar}sp{lcub}-2{rcub}{dollar}day{dollar}sp{lcub}-1{rcub}{dollar}mmHg{dollar}sp{lcub}-1{rcub}{dollar}) and was within the required 0.08-14.76gm{dollar}sp{lcub}-2{rcub}{dollar}day{dollar}sp{lcub}-1{rcub}{dollar}mmHg{dollar}sp{lcub}-1{rcub}{dollar} range for an effective barrier for the raisin and cereal mixture. Larger average a{dollar}sb{lcub}rm w{rcub}{dollar} gradients resulted in higher water vapor permeance due to hydration induced swelling of the edible barriers. DTA analyses showed that barriers were in their rubbery state and thus more susceptible to hydration. Permeance decreased as the fatty acid chain length increased from capric to stearic and increased from stearic to arachidic. Mathematical modeling showed that the barriers containing stearic and palmitic acid can be effectively modeled as a permeance in Series while the barriers containing arachidic and behenic acid are most effectively modeled via emulsion models at a volume fraction of 30%. EFM/DIA results show that above a volume fraction of 30% stearic acid, an interlocking network is formed which is a partial explanation for the low rate of water vapor permeance through the barrier containing stearic acid. In a food polymer science vein, DTA, EFM/DIA and mathematical models were applied to define as well as explain the water vapor barriers properties of edible barriers.