Research On The Chemical Process Of Vitamin C And Sodium Benzoate In Model And Real Food System

As a natural antioxidant existing in many vegetables and fruits, ascorbic acid (vitamin C) is often added to foods in the manufacturing process as a vitamin supplement or fortifier and promoted as an antioxidant. With a relative low price, sodium benzoate is widely used as a preservative in the food industry. When both of them are contained in the food system, a series of reactions can take place and lead to the production of benzene which is carcinogenic and other chemicals. Because of the risk of being harmful to human health, it is always the focus to study the reactions between Vc and sodium benzoate at home and abroad. In this paper, part of their products under the existence of transition metals were distinguished, the reaction process and affecting factors were studied, the contents of Vc and sodium benzoate in several soft drinks were determined and the stability of them were investigated.The experimental part involved the derivatization gas chromatography, UV-vis and HPLC method. The qualitative analysis of reaction products was realized by the traditional liquid-liquid extraction or solid phase extraction of the target chemicals with ether. Followed by the derivatization of the residues after dried with BSTFA (N,O-bis(trimethylsilyl) trifluoroacetamide) + TMCS (trimethylchlorosilane) reagent and then the separation of trimethylsilyl derivatives using GC-MS. In the section of kinetic process study, both online UV-vis method and offline HPLC method were taken advantage of. A simple and quick isocratic elution procedure was developed with HPLC for the simultaneous determination of Vc and sodium benzoate in beverages with complicated matrix.Three isomeric hydroxybenzoates and three isomeric dihydroxybenzoates, which are o-hydroxybenzoic acid, m-hydroxybenzoic acid,p-hydroxybenzoic acid, 2,3-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid and 3,4-dihydroxybenzoic acid, were measured as products of hydroxyl radical attack on benzoate. Besides, o-dihydroxybenzene and p-dihydroxybenzene were detected as the decarboxylation products. From the kinetic process study, the following conclusions have been drawn: the reaction process of sodium benzoate and formation of the products correspond to the kinetic model of the zero order reaction; cupric sulfate acts as a catalyst in the reaction system, which is reduced immediately at the beginning and then gradually oxidized; Vc promotes the formation of hydroxyl radicals as well as scavenges them from the system. the higher the concentration of sodium benzoate is, the faster the free-radical substitution of benzoic acid takes place; temperatures and pH values influence the rate of the reaction dramatically.Fanta and Mirinda together with other four soft drink samples contain either Vc or sodium benzoate. Considering the decrease of Vc or sodium benzoate contents after unsealed during storage and the increase of instability of Vc when Sodium benzoate was added to the beverages, it was deduced that in Mirinda, which is marked to have Vc as an ingredient, Vc diminished because of the reaction between it and sodium benzoate.