| Heterocyclic amines are a class of polycyclic aromatic compounds produced in protein-rich foods during thermal processing,which are carcinogenic and mutagenic.2-Amino-1-methyl-6phenyl-imidazo[4,5-b]pyridine(PhIP)is the most abundant heterocyclic amine produced in the cooked meat products,long-term intake will increase human suffering the risk of cancer.At present,there are many research reports on the formation mechanism and inhibition method of PhIP under high temperature heating conditions.Adding antioxidants such as polyphenols is an effective method to inhibit PhIP formed in meat products.In addition,the processing method has an important influence on the formation of PhIP.It has been shown that the microwave pretreatment or direct microwave heating can reduce the PhIP concentration in the meat product.Previous research of this group have found that caffeic acid has a significant inhibitory effect on PhIP formation under microwave field,compared with other polyphenols,but its inhibition mechanism is still not clear.In this paper,the structural change of caffeic acid under different heating conditions was analyzed.The effect of caffeic acid on the antioxidant activity of PhIP system was investigated.The reaction product of caffeic acid and PhIP intermediate was speculated and verified in the chemical system.(1)The effect of caffeic acid on the inhibition of PhIP formation under microwave field: The effect of addition concentration of caffeic acid and heating time on the amount of PhIP was investigated.It was found that the formation of PhIP decreased with the increased of caffeic acid added,and the inhibition rate of caffeic acid to PhIP under microwave conditions was always higher than conduction heating.With the prolongation of heating time,the inhibition rate of caffeic acid to PhIP decreased gradually under the two heating modes,but the inhibition rate under microwave field was higher than that of conduction heating.It may be that microwave promoted the dissolution of caffeic acid in the system and promoted it absorb more energy,so that the inhibition rate of caffeic acid to PhIP maintained a relatively high level.(2)The effect of microwave heating on the thermal stability of caffeic acid: The content of caffeic acid in two heating modes was investigated.It was found that the thermal degradation of caffeic acid occurred with the prolongation of heating time.The degradation rates of caffeic acid in microwave and conduction heating systems were 25.9%~36.7% and 19.7%~33.5%,respectively,but the degradation rate of caffeic acid under microwave field was higher than conduction heating.Subsequently,the degradation products of caffeic acid under microwave field were analyzed.Through purification and structural identification of main degradation products,it was found that the main degradation products of caffeic acid under microwave and conduction heating was 4-vinylcatechol with a molecular weight of 136.The amount of 4-vinylcatechol increased as the amount of caffeic acid added and the heating time increased.(3)Study on the inhibition mechanism of caffeic acid on PhIP under microwave field: The change of inhibition rate of phenylacetaldehyde in the PhIP model system was studied.It was found that the amount of phenylacetaldehyde in the system decreased with the increase of caffeic acid.In addition,by isolating,purifying and identifying the caffeic acid-phenylacetaldehyde adduct in caffeic acid-PhIP system.It was determined that the product was 3-(3,4-dihydroxyphenyl)-2-phenylbutyraldehyde.By analyzing the peak areas of the two targets in the caffeic acid-PhIP system under different conditions,it was found that the concentration of the 3-(3,4-dihydroxyphenyl)-2-phenylbutyraldehyde increased with the addition of caffeic acid,and it increased first and then decreased with the heating time,heating excessive time may lead to degradation of the target.(4)Effect of caffeic acid on the antioxidant activity of PhIP chemical model system: Adding caffeic acid to PhIP system,the intracellular and extracellular antioxidant changes of the system were determined.It was found that the scavenging ability of both free radicals DPPH· and ABTS·+ in the PhIP system heated with caffeic acid is higher than that of the separately heated caffeic acid and PhIP model system,and the results of scavenging ability of active oxygen are also consistent. |
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