Nanoparticles from a Gold Complex with Sulfite Ion as Ligand: Preparation and Characterization

ABSTRACT

Gold colloidal nanoparticles (GNPs) were prepared by reducing a complex of Au⁺. Na₃Au(SO₃)₂ with sodium citrate. The procedure provides control of the dimension of nanoparticles produced, which is a function of reaction time and concentration of reactants. The nanoparticles were separated by centrifugation and their characteristics and dimensions were studied using UV-Vis and IR spectroscopy and transmission electronic microscopy (TEM).     

Storage Stability of Orange Juice Concentrate Packaged Aseptically

Orange juice concentrates were packaged aseptically by a “Dole” aseptic canning machine using 6 oz metal cans. The final juice products (11°, 34°, 44°, 58° Brix) were stored between ?18° and 36°C and tested periodically for nonenzymatic browning, ascorbic acid destruction, furfural and sensory changes. Nonenzymatic browning, the main deterioration phenomena in these products, was satisfactorily retarded at 12°C or lower. Ascorbic acid destruction rate constant was dependent on temperatures between 5 and 25°C, and was affected by degree of juice concentration. Furfural accumulation in juice was higher than that in 58° Brix concentrate. Orange juice concentrate of 58° Brix did not show flavor changes after storage at 5°C or 12°C for 17 or 10 months, respectively, when evaluated after reconstitution to 11° Brix.     

Ascorbate Oxidase in Mature Orange Peel

Evidence of the occurrence of ascorbic acid oxidase in the peel of mature orange is presented. The enzyme was found to be insoluble and located in albedo only. It is specific for ascorbic acid but not for catechol and is oxygen-dependent, with pH optimal activity of 6.5. The ascorbic acid oxidase acitivity was inhibited by high temperature, a pH below 3.5, and copper-chelates such as sodium azide and sodium dithiocarbamate. Blanching and decreasing the pH of the peel to 3.5 are recommended to achieve maximum stability of ascorbic acid in orange peel.     

Thin-Layer Chromatographic Study on the Lipid Components of Cocoa Beans and Cocoa Butter

SUMMARY— After thin-layer chromatography, cocoa bean cotyledon section presented only one chromatographic spot whereas cocoa butter showed five spots. Apparently, the lipids naturally occurring in cocoa beans are not modified during farm fermentation.