Study On The Reaction And Mechanism Of Acrylamide And Thiol Flavor Substances In Food Processing

Acrylamide is often produced in different amounts during the thermal processing of starchy foods.As a reactive molecular compound,acrylamidewill react with other chemically active ingredients when they coexist in the same food processing system.Thiol flavor is an important food additive.The aroma of food produced by thermal processing also contains many thiol compounds.Sulfhydryl group has very strong nucleophilic activity,and thiol compounds have good reactivity with olefins.Therefore,acrylamide and thiol aromatic substances may have chemical reactions in the process of food processing and storage.So that the existing state of acrylamide in food has changed.This paper systematically studies the influence factors and reaction mechanism of acrylamide and thiol flavor effects in food processing conditions,these studies provide new ideas and vision for the development of the new mechanism of inhibition of acrylamide.The main results are shown as follow:(1)the establishment of analog reaction system and determination method of AcrylamideFirstly,the acrylamide detection methods of GC-MS,HPLC-MS and HPLC-UV were established,and methodological demonstration was carried out.It can be seen that HPLC-UV can also be used as a reliable and fast analytical method for the simulation reaction system.Two simulated reaction systems of HTHH(High temperature and high humidity)and HTLH(high temperature and low humidity)were established based on the actual food processing.The effects of the amount of butanethiol,heating temperature,heating time and pH on the reaction of acrylamide and butanethiol in two kinds of simulation system were discussed through the single factor experiment and response surface experimental design.On this basis,chemical model for the reaction of butanethiol with acrylamide in the HTHH and HTLH simulation systems was established by Response surface methodology.By calculation and integer of parameters,the optimum reaction conditions were obtained for the two reaction systems.(2)Reactivity of mercaptan with different structures to acrylamide was studied.Propyl mercaptan,butanethiol,2-methyl-1-mercaptan,3-methyl-1-mercaptan,3-methyl-2-mercaptan,1,2-ethanedithiol,1,3-dimercaptopropane,1,6-hexanedithiol and furfuryl mercaptan were employed to study as fatty thiols.The results showed that the reaction order was dihydric mercaptan>primary mercaptan>secondary mercaptan.The length and steric hindrance of aliphatic chain have little effect on the reactivity of aliphatic thiol with acrylamide in the case of high temperature.Phenthiol,2-methylbenzenethiol,2-methyl-3-furanthiol,2,5-dimethylfuran-3-thiol and thiophenethiol were employed to study as aromatic thiols.Our study show that(1)the alkyl donating electron substituent on the aromatic ring has little effect on the activity of the reaction;(2)The reaction activity of aromatic thiols and acrylamide in HTHH simulation system is much higher than that of HTLH simulation system.Experiments were carried out on a variety of compounds containing carbonyl,amino and thiol compounds.The experimental results showed that these compounds reacted strongly with acrylamide and showed strong reactivity.(3)study on the reaction mechanism of thiol flavors and acrylamide in simulation systemFour kinds of 3-alkyl amides were prepared and their structures were characterized and identified.Under the same conditions,the 3-alkyl amides was heated,and the results showed that the reaction between thiol and acrylamide was irreversible.The presence of thiol acrylamide oligomers was found by HPLC-MS analysis of the reaction compounds of thiol and acrylamide.The experiments showed that free radicals played an important role in the reaction between thiol and acrylamide by isolating oxygen and adding antioxidants.The disappearance rate of acrylamide was reduced from 83.21%to 41.02%when the reaction of cysteine and acrylamide was carried out under the condition of adding antioxidants and isolating oxygen in the HTLH simulation system.But the same experiment showed that the disappearance rate of acrylamide decreased from 85.66%to 72.34%in the HTHH simulation system.It indicated that the degree of free radical participation was different under different reaction conditions.According to the above experimental facts,the reaction mechanism of thiol and acrylamide in different simulation systems was analyzed and summarized.(4)the influence of the presence of food matrix components on the reaction of thiol with acrylamideThe presence of beta cyclodextrin can significantly promote the reaction of thiol with acrylamide.Characterized by ~1H NMR,the results showed that butanethiol entered into the cavity of cyclodextrin.The hydroxyl groups of thiol and C6 of beta cyclodextrin have formed hydrogen bonds.Therefore,the sulfur hydrogen bond energy is weakened,and the nucleophilic attack ability of sulfur atoms is enhanced.In addition,20 common amino acids in food were introduced into the reaction system of thiol and acrylamide to investigate the effect of amino acids on the reaction of thiol with acrylamide.The results showed that the addition of lysine,arginine,histidine and cysteine significantly promoted the reaction of thiol with acrylamide.With the addition of cysteine,the disappearance rate of acrylamide was 100%.While the disappearance rate of acrylamide increased to 65.43%,74.28%and 44.71%,respectively,compared with 29.84%in the control group with the addition of lysine,arginine and histidine to the reaction system.The effect of the concentration of inorganic salt on the reaction of mercaptan with acrylamide was also investigated by the concentrations of 0.01,0.02,0.05,0.1,0.2 mol/L phosphate buffer,and the concentrations of 1,0.5,0.2,0.1,0.01mol/L of Sodium Chloride Solution.The results showed that the disappearance rate of acrylamide showed a downward trend under the above conditions.