Oxidation of encapsulated oil in tailor-made cellular solid.
A cellular alginate solid containing oil was prepared by freeze-drying. The oil was incorporated in the matrix by emulsification in the pre-gel state. The alginate-oil gels were immersed in 60 degrees Brix sucrose solution for various periods, before freeze-drying. The extent of the collapse expressing the reduction in sample volume was affected by immersion duration and freeze-drying conditions. Sucrose diffusion during immersion followed an exponential pattern. Effective diffusivity calculated using nonlinear regression gave a value of 3.64 x 10(-)(10) m(2)/s. The effect of relative humidity on water content calculated on a dry basis excluding sucrose showed a significant increase in water content at 75% RH. Image analysis was utilized to quantify the area of the encapsulated oil droplets. The area of the droplets was divided into four subregions defined as (0.02-0.1) x 10(-)(12), (0. 1-1.0) x 10(-)(12), (1-10) x 10(-)(12), and (10-100) x 10(-)(12) m(2). A distribution resembling a Gaussian bell distribution with a maximum of 54% for the (1-10) x 10(-)(12) m(2) area range was found. The number of oil droplets was almost constant for the first three area regions, and then decreased markedly. Oxidation index was not effected by porosity at 0 and 22% RH. A 75% RH and porosity above a critical value of ca. 0.45 was found to increase oxidation significantly. Samples immersed for less than 5.5 h in sucrose solution were mechanically stronger after equilibration at 0 and 22% RH when compared to their counterpart equilibrated at 75% RH. Immersion for more than 24 h resulted in similar mechanical strength irrespective of the RH.
Rassis
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Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel.
Nussinovitch
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Saguy
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D008422:Materials Testing; D009821:Oils / Q000737:chemistry*; D010084:Oxidation-Reduction
D009821:Oils