Study On Enrichment,Detection And Inhibition Of Heterocyclic Aromatic Amines In Cantonese Baked Foods

Cantonese baked foods are widely loved by the public because of their exquisite materials,delicate appearance and sweet&smooth taste.However,due to the high content of oil,sugar and animal protein in its formula,it will inevitably generate carcinogens such as heterocyclic aromatic amines（HAAs）during thermal processing,and long-term consumption will increase people’s risk of cancer and cardiovascular disease.Therefore,it is very important for the healthy and sustainable development of Cantonese bakery industry to develop sample pretreatment methods suitable for the efficient detection of trace hazards and new processing techniques to reduce the generation of hazards.In this thesis,based on the characteristics of strong structural design and surface modification of covalent organic frameworks,a magnetic carboxyl-functionalized covalent organic framework composite for the selective enrichment of HAAs was designed,and a corresponding MSPE-HPLC/MS method was established for the efficient detection of trace HAAs in Cantonese baked foods.Based on this method,the addition of myricetin on the formation of heterocyclic amines in the simulated system and the corresponding inhibition mechanism were systematically investigated,as well as the effect on the basic sensory characteristics of Cantonese mooncakes,and the adducts of myricetin and HAAs intermediates and their potential biological activities were further excavated.This study shows high academic value and theoretical guiding significance for the efficient detection of trace hazardous substances in food thermal processing,the cooperative regulation between hazardous substances suppression and food sensory quality,and the creation of functional Cantonese baked goods.Based on the structural characteristics of HAAs,Tp Pa and Tp BD were functionalized using bottom-up method through synergistic regulation of the crystallinity,porosity and carboxylation degree to give Tp Pa-（COOH）₂ and Tp BD-（COOH）₂.The effect of carboxyl modification on the structural characteristics of these two materials and their affinity to HAAs was systematically studied.The results showed that the carboxyl-modification significantly reduced the crystallinity of Tp BD,and reduced the BET surface area of Tp Pa and Tp BD from285.9 and 161.1 m²/g to 87.6 and 43.5 m²/g,respectively.They both reached adsorption equilibrium within 30 min,and the theoretical maximum adsorption capacity of Tp Pa-（COOH）₂and Tp BD-（COOH）₂were 0.5～155.8 mg/g and 0.3～4.9 mg/g.By providing more negative electrostatic potential regions and increasing the maximum electrostatic potential of the binding sites,the carboxyl-modification significantly improved the adsorption selectivity and maximum adsorption capacity of carboxyl-modified COFs to HAAs.Affected by crystallinity,porosity and carboxylation degree,Tp Pa-（COOH）₂shows significantly higher HAAs affinity and matrix anti-interference ability than Tp BD-（COOH）₂.Hydrogen bonding,π-πconjugation and C-H/LP···πconjugation jointly drove the non-covalent binding of Tp Pa-（COOH）₂ to HAAs.Using amino-modified magnetic Fe₃O₄ as the core,a magnetic carboxyl-functionalized composite Fe₃O₄@DOPA-Tp Pa-（COOH）₂ was prepared.The structural characteristics of this material and its HAAs adsorption behavior were explored.MSPE procedure was optimized to establish a corresponding MSPE-HPLC/MS method for the enrichment and detection of HAAs in Cantonese mooncakes.The results showed that the BET surface area of this material is 130.7m²/g,and it only takes 1 min to completely separate after adsorption using a magnet with the reusability of at least 3 times.The LOD of this method is 0.01～7.01 ng/g;the LOQ is 0.02～8.82 ng/g;the HAAs recoveries are 72.96～126.49%（5 ng/g）,62.12～118.30%（50 ng/g）and63.69～126.86%（100 ng/g）;the intra RSD is 0.9～8.3%,and the inter RSD is 1.5～11.8%.Taking the simulated system and the Cantonese mooncake as the study objects,the effect of myricetin on the formation of HAAs and the inhibition pathways,as well as the effect on the texture and flavor of Cantonese Wuren ham mooncakes,were systematically investigated.The results showed that when the addition amount was 0.2 m M,the inhibition of myricetin on the formation of HAAs in the simulated system was 43.7～85.6%.The inhibition of myricetin on the content of formaldehyde,acetaldehyde,phenylacetaldehyde,2,5-dimethylpyrazine and total carbonyl are 50.0%,64.0%,45.5%and 39.0%,and 91.6%,respectively.The key pathway of myricetin to inhibit the formation of HAAs is to form adducts with Strecker aldehydes,and the myricetin-phenylacetaldehyde adducts were detected in Cantonese mooncakes.When the addition amount was 0.5%,the inhibition of myricetin on the formation of HAAs in Cantonese Wuren ham mooncakes was 54.4～81.8%.There was no significant effect on its texture properties with the addition of myricetin,but its bitter aftertaste and astringent aftertaste slightly increased.The total content of their main aroma components was partially increased,and the umami taste was significantly increased.Based on the key pathway of myricetin to inhibit the formation of HAAs,two myricetin-phenylacetaldehyde adducts BYQ-2 and BYQ-3 were obtained by preparative HPLC method and their structures were identified.Free radical scavenging ability of these adducts and their inhibition ofα-glucosidase and CYP450 1A2.The free radical scavenging ability of these adducts and their inhibitory ability onα-glucosidase and CYP450 1A2 were investigated.The results showed that the greatest absorption wavelengths of BYQ-2 and BYQ-3 with a Mw of420 shifted towards short wavelengths,and the reaction positions of these two adducts were at C-8 and C-6 of myricetin A ring,respectively.Myricetin and its derivatives showed mixed inhibitory types forα-glucosidase,and BYQ-2 has the highest binding energy（-7.75 kcal/mol）and inhibitory ability(IC₅₀=10.32μg/m L)forα-glucosidase.Both BYQ-2 and BYQ-3 showed better inhibition ability（IC50=5.44 and 4.93μg/m L）and binding energy（-8.19 and-9.31kcal/mol）to CYP450 1A2 than myricetin.Hydrogen bonding and hydrophobic interactions are the most important driving forces for the binding of myricetin and its derivatives to these two enzymes.In this thesis,starting from the structural design of new sorbents for MSPE,a magnetic carboxyl-modified covalent organic framework composite that can selectively adsorb HAAs was obtained through carboxyl-modification and magnetic copolymerization.Then,a corresponding MSPE-HPLC/MS method was developed for the efficient enrichment and detection of HAAs in Cantonese baked foods.On this basis,the inhibitory effect of myricetin on the formation of HAAs in Cantonese mooncakes and the inhibition mechanism,as well as the sensory characteristics of the corresponding products,were revealed.The structural formula of myricetin-active intermediates adducts,and their potential biological activities were clarified.This thesis provides technical support and theoretical guidance for the safety monitoring and functional improvement of Cantonese baked foods.