The effects of sucrose syrup concentration (40-70 g/100-g solution) and temperature (40-90C) on water loss and sucrose uptake by mango mesocarp slices during osmotic dehydration were investigated. The effective diffusivities for mass transfer were determined using the slope method based on the Fickian diffusion model. Water loss and sucrose uptake were proportional to the square root of osmotic contact time, implying that the process is Fickian. The specific mass transfer rate constants and effective diffusivities (D e ), derived from Fick's unsteady-state diffusion equation, increased with temperature and sucrose syrup concentration. D e values for water loss and sucrose uptake, which ranged between 2.59 ¥ 10 -6 to 5.12 ¥ 10 -6 m 2 /h and 1.70 ¥ 10 -6 to 4.14 ¥ 10 -6 m 2 /h, respectively, were related to absolute temperature using an Arrhenius-type relationship. The activation energies, which fell in the range previously reported for diffusion-controlled processes, increased with sucrose syrup concentration and varied from 9.74 to15.16 KJ/mol. 3 Corresponding
Laboratory investigations into the possibility of using local Nigerian clays in refining the Nigerian crude palm oil revealed that the Okija clay may possess some potential as an adsorptive cleanser in the refining process. Activated bentonite was used as the standard clay of comparison, and the performance of two local natural clays, leached with various concentrations of sulfuric acid, was evaluated for their use as alternative adsorptive cleansers in refining Nigerian crude palm oil. Measurements of peroxide values, para‐anisidine values, carotene content and stabilities of the oils using the active oxygen method were used in assessing the relative performance of the clays.The clays exhibited similar trend of effects on identical batches of alkali‐neutralized palm oil. In one set of experiments poor results were obtained when the degummed and alkali‐neutralized palm oil was treated with clays leached with sulfuric acid at concentrations of 1M and 4M. Better results were obtained at acid concentrations of 2M and 3M. Bentonite proved better than Okija clay when the leaching was performed with 2M H2SO4, but both clays had comparable effectiveness when 3M H2SO4 was used for leaching. The Nsu clay gave the least encouraging results. In another series of experiments the results showed that for various dosages of clay, up to 3% by weight of the oil to be refined, the oxidative stability of the processed oil was reasonably good for an oil which was neither deodorized nor treated with antioxidants.
Lacquered metal cans, green glass bottles, amber glass bottles, clear glass bottles and clear plastic bottles filled with freshly produced Nigerian crude palm oil were stored in direct sunlight (40±1°C) and in the dark (27±1°C). Assessment of the stability of the oils towards hydrolytic and oxidative deterioration was made periodically by measuring the free fatty acid, peroxide and anisidine values over a period of 98 days. The study showed that crude palm oil packaged in plastic bottles and clear glass bottles recorded higher total oxidation values than oils packaged in either lacquered metal cans or amber and green glass bottles. Lacquered metal cans gave the greatest protection against oxidation. Oxidation proceeded faster in cases where the packaging materials were stored in direct sunlight.
Thermal/enzymic degradations of ascorbic acid in whole, chopped and pureed fluted pumpkin leaves were studied from 60 to 100C (5–60 min). Degradation of ascorbic acid followed first order kinetics with the rate constants having maximum values at 80–90C. Ascorbic acid degradation exhibited strong deviation from linearity in thermal resistance, Arrhenius and absolute reaction rate plots at 100C indicating inactivation of the oxidative enzymes around 90C. At lower temperatures (60–90C) ascorbic acid was more stable in the whole and chopped leaves than in the pureed system. Activation energies ranged from 49 to 50.8 KJ mol−1. At 100C, the puree matrix offered more protection to ascorbic acid.
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