The Stability Of Vitamin A Under The Influence Of Isopropylbenzene Hydroperoxide And Aeration Conditions

Due to the conjugated double bonds and hydroxyl or ester functional group, vitamin A is susceptible to light, heat, oxygen and peroxide, resulting in changes in molecular structure and performance. As vitamin A is inevitably exposed to peroxide and aeration conditions during its production, storage and application, it is important to study the stability of vitamin A under the influence of peroxide and aeration conditions for determing the shelf life of fortified food and exploring the stability technology of vitamin A.To simulate the influence of peroxide on vitamin A, isopropylbenzene hydroperoxide (CHP) was used in this paper. Through the analytical methods of high performance liquid chromatography-diode array detector (HPLC-DAD), gel permeation chromatography (GPC) and high performance liquid chromatography-mass spectra (HPLC-MS), the influence of temperature, initial concentration of vitamin A and CHP on the stability of vitamin A was studied in the absence of light and oxygen. The results showed that when the concentration of CHP was1%(mCHP=w%xmvitamin A), vitamin A underwent dimerization. The dimerization reaction rate increased with the temperature rise and the initial vitamin A concentration decrease. When the concentration of CHP was10-50%, vitamin A underwent dimerization and oxidation at the same time firstly. As the reaction progressed, the oxidation products and vitamin A underwent dimerization together. Dimerization mechanism and four most probable dimers structures were also inferred with the help of IR analytical rusults, free radical resonance and free radical stability theory.Through changing the agitation speed and temperature, it was found that the oxidation of vitamin A under aeration conditions was slow, and the overall reaction rate, which was first order with respect to vitamin A, was controlled by chemical reaction. The overall reaction rates of vitamin A with pure oxygen and air in the temperature range from40℃to80℃were obtained. Furthermore, the corresponding reaction activation energies and pre-exponential factors were61.92kJ·mol-1,4.70×105h-1for pure oxygen and96.57kJ·mol-1,2.62×1010h-1for air.