Study On The Loss Rule Of γ-oryzanol In Rice Bran Oil Under Heat Treatment

γ-oryzanol has antioxidant,anti-cancer,anti-inflammatory and other physiological activities,widely used in food,cosmetics,functional materials,medicine and health and other fields.As the main source ofγ-oryzanol,excessive refining of rice bran oil and cooking will cause the loss ofγ-oryzanol,resulting in the reduction of oil quality.Therefore,based on the establishment ofγ-oryzanol detection method in the simulated system,this study explored the loss rule ofγ-oryzanol and its main components in the simulated system and rice bran oil system respectively,and further determined its influence on the thermal stability of rice bran oil.In order to provide a reference value and theoretical basis for the moderate processing of rice bran oil and the development and utilization ofγ-oryzanol.Firstly,the High performance liquid chromatography method for detecting four major components ofγ-oryzanol in the simulated system was established.Methanol:acetonitrile(1:1,v/v)was used as the mobile phase to separate the four main components ofγ-oryzanol.The method has good linearity in the concentration range of 20-1000μg/m Lγ-oryzanol.The standard curve equation R~2 of Cycloartenyl ferulate(CAFA),24-Methylenecycloartanyl ferulate(24MCAFA),Campesteryl ferulate(Camp FA)andβ-Sitosteryl Ferulate(Sito FA)was0.9986 to 0.9995.The instrument precision,sample repeatability,sample stability and sample recovery were verified.The results showed that the detection method was accurate,with less error,good repeatability and stability,which could be used for the quantitative analysis ofγ-oryzanol.Secondly,the loss rule ofγ-oryzanol and its main components in the simulated system under atmospheric pressure heating and nitrogen filling heating were studied.The results showed that the loss rate ofγ-oryzanol increased linearly with the extension of heating time under the two heating methods,and began to lose rapidly at 180°C.When the temperature was lower than 100°C,there was no significant difference in the thermal stability of the four components.At 140°C,CAFA and 24MCAFA were significantly higher than phytosterol ferulate,and 24MCAFA>CAFA>Camp FA>Sito FA when the temperature was higher than180°C.The loss rates ofγ-oryzanol and its main components under atmospheric heating were significantly higher than those under nitrogen heating.The total loss rates ofγ-oryzanol and its main components were 44.84%and 34.21%respectively at 260°C for 12 h,indicating that the loss ofγ-oryzanol was related to thermal oxidation.In the simulated system,the degradation process ofγ-oryzanol could be expressed by first-order kinetics.The degradation kinetic equation R~2 ranged from 0.8854 to 0.9984,and the degradation kinetic constant ranged from 0.005 to 0.087,and its value was related to the heating temperature and heating mode.Finally,the heat loss rule ofγ-oryzanol and its main components in rice bran oil system was studied,and the correlation between its loss rate and oil quality was analyzed.The results showed that the loss rate ofγ-oryzanol increased linearly with the extension of heating time under both heating methods,and began to lose rapidly at 220°C.Under the same heating conditions,the loss rate ofγ-oryzanol under atmospheric pressure heating was significantly higher than that under nitrogen filling heating.There was no significant difference under140°C heating.The difference under 220°C heating for 12 h was the largest(32.34%),and the loss rate ofγ-oryzanol under 260°C heating for 12 h was the highest(74.14%).The thermal stability of the four main components was similar under the two heating methods.When the heating temperature was lower than 140°C,there was no significant difference between the components.When the heating temperature was higher than 180°C,Camp FA>CAFA>24MCAFA>Sito FA.When heated at 260°C for 12 h,Sito FA had the highest loss rate(90.43%),while Camp FA only had the highest loss rate(62.24%).The degradation ofγ-oryzanol in rice bran oil was well described by first-order kinetics,R~2 was 0.9250～0.9956,and the degradation kinetic constants were 0.015～0.186.When the heating temperature was higher than 220°C,there was a significant correlation betweenγ-oryzanol loss rate and oil quality indexes(P<0.01),and the correlation was enhanced with the increase of temperature.When the heating temperature was higher than 100°C,the correlation between the loss rate ofγ-oryzanol and its four main components and the total oxidation value was extremely significant(P<0.01),indicating that the deepening of the oxidation degree of oil would also promote the loss ofγ-oryzanol.