title: Degradation kinetics of gamma-oryzanol in antioxidant-stripped rice bran oil during thermal oxidation.
abstract: Gamma-oryzanol, a group of phytosterol ferulates found in rice bran, possesses antioxidative activity and other bioactivities. The kinetics of thermal degradation of gamma-oryzanol in stripped rice bran oil (SRBO) were investigated under heating at 132, 160, 192 and 222 degrees C for 480, 140, 60 and 50 h, respectively. Losses of the overall gamma-oryzanol and its components (cycloartenyl ferulate, 24-methylene cycloartanyl ferulate, campesteryl ferulate and beta-sitosteryl ferulate) could be expressed by the first-order kinetics model. The rate constant of thermal degradation of gamma-oryzanol increased with increasing heating temperatures. The temperature dependence of the obtained rate constants was found to obey the Arrhenius equation. Campesteryl ferulate showed slightly more thermally resistant than other components at temperature lower than 160 degrees C. However, the change in the absorbance from 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay as a function of heating time exhibited the same pattern for the SRBO with and without gamma-oryzanol for all studied heating temperatures.
authors.affiliation: Department of Food Technology, Faculty of Engineering and Industrial Technology, Silpakorn University, Nakhon Pathom, Thailand. kpramote@su.ac.th
authors.forename: Pramote
authors.initials: P
authors.lastname: Khuwijitjaru
authors.forename: Thippawan
authors.initials: T
authors.lastname: Yuenyong
authors.forename: Rungnaphar
authors.initials: R
authors.lastname: Pongsawatmanit
authors.forename: Shuji
authors.initials: S
authors.lastname: Adachi
mesh_terms: D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism*; D001713:Biphenyl Compounds / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D006358:Hot Temperature; D007202:Indicators and Reagents; D007700:Kinetics; D010084:Oxidation-Reduction; D010666:Phenylpropionates / Q000737:chemistry / Q000378:metabolism*; D010840:Phytosterols / Q000737:chemistry / Q000378:metabolism*; D010851:Picrates / Q000032:analysis; D010938:Plant Oils / Q000737:chemistry / Q000378:metabolism*; D000073879:Rice Bran Oil
chemical_list: D000975:Antioxidants; D001713:Biphenyl Compounds; D007202:Indicators and Reagents; D010666:Phenylpropionates; D010840:Phytosterols; D010851:Picrates; D010938:Plant Oils; C004931:1,1-diphenyl-2-picrylhydrazyl; D000073879:Rice Bran Oil; C013172:gamma-oryzanol