Suppressive effect of alkyl ferulate on the oxidation of microencapsulated linoleic acidThe oxidation processes of linoleic acid mixed with ferulic acid or the 1-pentyl, 1-hexyl and 1-heptyl ferulates, encapsulated with gum arabic or maltodextrin, were studied. The alkyl ferulates had a higher antioxidative effect than ferulic acid, but there was no significant difference among the three alkyl ferulates. Suppression of the oxidation by 1-hexyl ferulate or ferulic acid was more effective at the higher molar ratios of the additive to linoleic acid. The processes were analyzed using the Weibull equation to evaluate the rate constant, k, and the shape constant, n. Although the k values for linoleic acid encapsulated with gum arabic were lower than that with maltodextrin, the suppressive effect of the alkyl ferulates was more remarkable for linoleic acid encapsulated with maltodextrin than with gum arabic because of the non-antioxidative ability of maltodextrin. Because the partition coefficient of the alkyl ferulates was much greater than that of ferulic acid, most of the alkyl ferulates would be located in the linoleic acid phase of the microcapsules and effectively suppress the oxidation of linoleic acid.
Two types of lipids rich in arachidonic acid content were encapsulated using various saccharides as the wall material, and the oxidation processes of the encapsulated lipids were measured at /*ῌ and +,ῌ relative humidity. One of the lipids contained arachidonoyl residue at a content of ca. .*ῌ, and another was a structured lipid, the major component of which was +,--octanoyl-,-arachidonoyl glycerol. Microencapsulation e#ectively retarded their oxidation. In particular, among the tested saccharides, soluble soybean polysaccharide and gum arabic were the best two wall materials for the suppression of both lipids.
The apparent distribution coefficients, K app , of some mono-, di-and trisaccharides onto cation-exchange resins in the sodium-ion form and having the divinylbenzene (DVB) contents of 4, 6 and 8% were measured at 25℃. A method for simultaneously estimating the swelling pressures of the resins and the binding constants, B, of the saccharides to the sodium ion was proposed. By applying the method to the K app values of mono-and disaccharides, the swelling pressures of the resins having the DVB contents of 4, 6 and 8% were estimated to be 18.9, 30.8 and 37.8 MPa, respectively, and the B values of the mono-and disaccharides were also estimated simultaneously. The B values of the trisaccharides were calculated using the estimated swelling pressures. The B values ranged from 0.24 to 2.2 L/mol. The tri-, di-and monosaccharides had higher B values in this order. There was a tendency that the solute, which can form a tridentate complex with the sodium ion, contains high numbers of axial-equatorial and equatorial-equatorial complexing hydroxyl groups.
The elution curves of caffeine, vanillin, coumarin, and methyl paraben, which have different hydrophobicities, in a bed packed with porous methyl methacrylate resin, were measured by the pulse response technique using methanol-water mixtures with various methanol contents as the eluent in the temperature range of 30°C to 200°C. The more hydrophobic solutes eluted at a slower rate under all conditions. All solutes eluted faster with eluents with higher methanol contents and at higher temperatures. The distribution coeffi cients of the solutes to the resin under various conditions were evaluated by moment analysis of elution curves. The adsorption enthalpy changes, ∆H, of the solutes were estimated from the plots of the distribution coeffi cients versus the reciprocal of absolute temperature. For the eluents with methanol contents higher than 75%, the ∆H values of all solutes were practically zero. This indicates that the solutes scarcely adsorbed on the resin. For eluents with lower methanol contents, solutes were eluted at a slower rate and their ∆H values were more negative. When water was used as an eluent, elution behavior showed the opposite tendency.
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