Synthesis Of Cinnamyl Methyl Fumarate And Studies On Its Application In Litchi Fresh-keeping

Food is very important to the people. In the production of food, it is crucial that proper measures are taken to ensure the safety and stability of the product during its whole shelf life. So it is a hot issue in food science to develop high-performance, broad-spectrum and low toxicity preservatives. The relationship between structure and antimicrobial activity of preservatives showed that dimethyl fumarate (DMF) is an effective preservative containing two α,β-unsaturated carbonyl, but it is banned to be used in food because of its skin allergy. It is significant to study how use the effective group of α,β-unsaturated carbonyl and has no poisonous side effect. In the dissertation a new preservative -cinnamyl methyl fumarate (CMF) was designed and synthesized which has two α,β-unsaturated carbonyl as base group, cinnamyl as hydrophobicity group to increase its antimicrobial activity. Its antimicrobial activity and the effect in litchi fresh-keeping were also studied. In order to synthesize CMF, the following route was adopted: maleic anhydride react with cinnamyl alcohol to produce cinnamyl maleate, then isomerized and esterified. The optimum technology condition to synthesize CMF as following: maleic anhydride and cinnamyl alcohol (molar ratio 1:2) react under 95℃for 2~4h before the isomerization catalysts were added. Then the mixture maintained at 85℃~90℃for 2.5~3.0h before methol (molar ratio 1:6), 3% 1:1 HCl and BF3 mixture were added. Then react under 90℃for 4h. Content of water is one of the main factors to restrict the synthesis rate. The experiment adopted adding sulphuric acid to remove the water during esterification. The amount of sulphuric acid is 3%, adding at 0.5h~3.0h during esterification. The synthesis rate of CMF increased with adding times of sulphuric acid. When adding times reach seven, the synthesis rate of CMF increase to 87.6%. The cinnamyl fumarate is difficult to dissolve in water, and easy to dissolve in organic solvent. The solubility of CMF increases in water. It is also found that during esterification the crystal form change from a cluster of needle to lamellar crystal in bulk. The largest ultraviolet absorption wavelength of CMF is 218nm. The high pressure liquid chromatogram, gaseous phase chromatogram -mass spectrum were used to analysis the constitute of the material. The result showed that there are dimethyl fumarate, cinnamyl methyl fumarate and dicinnamyl fumarate in it. After purification, the contents of CMF can reach more than 90%. The experiment of CMF antimicrobial activity shows that: antimicrobial activity of CMF doesn't influence by the pH of environment. Under low pH, CMF can coordination with the environment to restrain the growth of the microorganism more effectively. When increase the concentration of CMF to 0.075%, the antimicrobial effect doesn't remarkably change with the increase of concentration. Changes of temperatures can't influence the antimicrobial activity of CMF. The minimal inhibitory concentration of CMF is lower than that of the food preservatives-potassium sorbate, sodium benzoate and hydroxybenzoate by 4~10 times. CMF is stability, difficult to sublimation. It overcomes the shortage of DMF, and hopeful to become a new food additive. 0.05%CMF can inhibit the growth of Peronophythora litchi Chen. Filming with 1%CMF, 10% critic acid and 10% membranes material, litchi can store under25~ 35℃(relative humidity 80%~90%) for 12days. From the results of SEM, we could find that fresh-keeping treatment could from a layer of manmade wax, that could keep the integrality of real pericarp of litchi, prolong its fresh period.