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The partition coefficient (K(p)) of the natural phenolic antioxidant compounds in the olive fruit between aqueous and olive oil phases was determined. The antioxidants of olive oil are either present in the olive fruit or formed during the olive oil extraction process. The antioxidants impart stability to and determine properties of the oil and are valuable from the nutritional point of view. The olive oil antioxidants are amphiphilic in nature and are more soluble in the water than in the oil phase. Consequently, a large amount of the antioxidants is lost with the wastewater during processing. The determination of antioxidants was performed using HPLC, and the K(p) was estimated to be from as low as 0.0006 for oleuropein to a maximum of 1.5 for 3,4-DHPEA-EA (di-hydroxy-phenyl-ethanol-elenolic acid, oleuropein aglycon). Henry's law fitted very well to the experimental data. The partition coefficients were also estimated by applying the activity coefficients of the antioxidants in the two phases using a predictive group contribution method, the UNIFAC equation. The K(p) values estimated with UNIFAC method were of the same order of magnitude but varied from the experimental values. Nevertheless, this method may be a rough predictive tool for process optimization or design. Because the K(p) values were very low, some changes in the process are recommended in order to achieve a higher concentration of antioxidants in the oil. A temperature increase may lead to increasing the partition coefficient. Also, limiting the quantity of water during oil extraction could be a basis for designing alternative processes for increasing the antioxidant concentration in the olive oil.

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AbslracL We consider periodic stmclures made of spheres embedded in a host material with a different dielectric function. We show how to calculate the reflection and transmission of electromagnetic waves bj a slab of the material parallel to a given nystallographic plane. ?he method of calculation is based an a doubling-layer scheme which oblmins the refleclion and transmission matrix elements for the mullilayer from thase of a single layer. The reflection and lransmision characleristics of die slab are related to the mmplex band structure of lhe photon field associated wilh lhe given aystallographic plane of the mmponding infinite crystal, which is introduced in the manner of the lowenergy electron diffraction theory. We present numerical resulll which demonstrate the appliCabi1iIy of the method to real systems of currenl interesl and point out mme interesting physics which arose fmm our Calculations. We show in particular that lhe non-degenerate tends of the photon field at the centre of the surface Brillouin zone do not couple to Ihe incident radiation, leading lo total reflection at normal incidence.

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The effective moisture diffusivity (D) in starch materials was estimated by the method of slopes of the drying curve and a computer simulation technique. Dlying data (moisture vs time) were obtained on slabs and spherical sampIes of hydrated and gelatinized starches in an air-dryer operated at 60-100°C and air velocity 2 m/set. The two methods gave similar results in high-amyIopectin starch gels of low porosity, where liquid diffusion might predominate during drying. Considerable differences behveen the two methods were found in hydrated granular starches and in porous high-amylose gels, where vapor diffusion might be the main water transport mechanism.