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Physical Properties of Rice Bran Wax in Bulk and Organogels
Author(s) -
Dassanayake Lakmali Samuditha K.,
Kodali Dharma R.,
Ueno S.,
Sato K.
Publication year - 2009
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-009-1464-6
Subject(s) - wax , differential scanning calorimetry , materials science , crystal (programming language) , chemistry , rice bran oil , carnauba wax , scanning electron microscope , soybean oil , chemical engineering , chromatography , bran , organic chemistry , food science , raw material , composite material , physics , computer science , engineering , thermodynamics , programming language
Differential scanning calorimetry (DSC), optical microscopy, and X‐ray diffraction (XRD) were used to examine the thermal behavior, crystal structure, and crystal morphology of rice bran wax (RBX) in bulk and oil–wax mixtures, and to compare them with those of carnauba wax (CRX) and candellila wax (CLX). The RBX employed in the present study was separated from rice bran oil by winterization, filtration, refinement, bleaching, and deodorization. The RBX crystals melted in the bulk state at 77–79 °C with Δ H melting = 190.5 J/g, which is quite large compared with CLX (129 J/g) and CRX (137.6 J/g). XRD data of the RBX crystals revealed O ⊥ subcell packing and a long spacing value of 6.9 nm. Thin long needle‐shaped crystals were observed in the mixtures of RBX and liquid oils [olive oil and salad oil (canola:soy bean oil = 50:50)]; therefore, the dispersion of RBX crystals in these liquid oils was much finer than that of CRX and CLX crystals. Organogels formed when the mixture of every plant wax and liquid oil was melted at elevated temperature and cooled to ambient temperature. However, the mixture of RBX and olive oil at a concentration ratio of 1:99 wt.% formed an organogel at 20 °C, whereas the lowest concentration necessary for CRX to form an organogel in olive oil was 4 wt.% and that for CLX was 2 wt.%. Observation of the rate of gel formation using DSC and viscosity measurements indicated that the gel structure formed soon after RBX crystallized, whereas a time delay was observed between the organogel formation and wax crystallization of CRX and CLX. These results demonstrate RBX’s good organogel‐forming properties, mostly because of its fine dispersion of long needle like crystals in liquid oil phases.