Now showing 1 - 3 of 3
  • Publication
    Extraction of bioactive secondary metabolites from Citrus Axima peel via pressurized hot water extractor for the synthesis of iron oxide nanoparticles
    ( 2024-06)
    Yi-Peng Teoh
    ;
    Nurdalilah Othman
    ;
    ;
    Zhong-Xian Ooi
    ;
    ;
    Saparu Walli
    ;
    Lian-See Tan
    ;
    Using bioactive secondary metabolites (BSM) from Citrus maxima peel extract, this work investigated a green method of synthesizing magnetite iron oxide (Fe3O4) nanoparticles (NPs). The BSM acts as a reducing cum stabilizing agent in the process. The optimization of the BSM parameters were conducted through response surface methodology (RSM). The optimal condition obtained in this study for pressurized hot water extractor (PHWE) extraction was temperature of 94.96 °C, solvent-to-solid ratio of 29.7 ml/g and extraction time of 27.6 min. BSM Yield of 49.31 % could be obtained based on this condition. The formation of Fe3O4 NPs were detected using the FTIR analysis with the absorption peaks observed at around 590 and 580 cm−1. X-ray diffraction results matched standard magnetite Fe3O4 patterns with planes at (220), (311), (400), (511) and (440). Field emission scanning electron microscopy (FESEM) results showed that the magnetite Fe3O4 NPs synthesized in this study predominantly appeared in spherical shape. The extraction process's kinetics were examined using various empirical models, including the Elovich’s model, Peleg’s model, Power law and parabolic diffusion model. All applied models were found to be well fitted with the measured data from experiment, with R2 values exceeding 0.9. Notably, the Peleg’s model exhibited the highest R2, the smallest RMSD, and the least significant p-values, indicating its superior performance.
  • Publication
    Comparative study on mechanisms of gases release from Ca-alginate beads
    ( 2024)
    Yee-Ming Peh
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    ; ; ; ; ;
    D.F.A. Riza
    ;
    N. Izza
    ;
    K. Gustinasari
    ;
    I.K. Maharsih
    ;
    W.B. Sunarharum
    ;
    M. Nurcholis
    ;
    B.S.D. Dewanti
    ;
    V.T. Widayanti
    ;
    E. Mufidah
    ;
    I. Qisthiya
    ;
    D. Karadag
    ;
    S. Idrus
    ;
    H. Umakoshi
    ;
    Y.C. Lee
    ;
    D. Fatchurrahman
    ;
    M. Zhu
    ;
    K.A. Omwange
    ;
    T. Addini
    Calcium alginate (Ca-alginate) beads have attracted considerable attention as carriers for the controlled release of volatile compounds due to their biocompatibility and tunable properties. This study aimed to compare the release of ethylene and carbon dioxide gas from Ca-alginate beads. Ca-alginate beads were prepared from a sodium alginate solution containing ethephon and calcium carbonate as the gas-forming agent. The resulting solution was then extruded into a calcium chloride solution. The gas release behavior was studied by monitoring the concentration of released gases over time using gas detectors. Extrusion tip diameter, alginate concentration and gas-releasing agent concentration were systematically varied to assess their effect on the gas release rate. The results indicated distinct release patterns for ethylene and carbon dioxide gas. Ethylene gas exhibited a relatively slower and sustained release, while carbon dioxide gas exhibited a more rapid release. Moreover, the bead size influenced the gas release, with larger beads displaying faster release rates for ethylene and carbon dioxide gas. The concentration of alginate also played a role in modulating the release kinetics, with higher alginate concentration resulting in slower gas release. The findings have implications for designing and optimizing Ca-alginate-based systems for agricultural applications, including plant hormone delivery and modified atmosphere packaging.