Effect and mechanism of polyphenols containing m-dihydroxyl structure on 2-amino-1-methyl-6-phenylimidazole [4, 5-b] pyridine (PhIP) formation in chemical models and roast pork patties

2-amino-1-methyl-6-phenylimidazole [4, 5-b] pyridine (PhIP) is a prevalent heterocyclic amine (HAA) found in heated processed meat. This study investigated the inhibitory impact of eight different types of polyphenols containing m-dihydroxyl structure on PhIP formation through a chemical model system. The structure-activity relationship and potential sites of action of polyphenols containing m-dihydroxyl structure were also analyzed. Then, the mechanism of inhibiting PhIP formation by kaempferol, naringenin and quercetin was speculated by UPLC-MS. Results showed that 8 kinds of polyphenols containing m-dihydroxyl structure had significant (P < 0.05) inhibition on the formation of PhIP in the chemical model system in a dose-dependent manner. In addition, PhIP was most significantly inhibited by naringenin at the same concentration, followed by kaempferol and quercetin (83.27%, 80.81% and 79.26%, respectively). UPLC-MS results speculated that kaempferol, naringenin, and quercetin formed a new admixture via an electrophilic aromatic substitution reaction with the intermediate product phenylacetaldehyde, preventing the formation of PhIP.

Unraveling the relationships between processing conditions and PhIP formation in chemical model system and roast pork patty via principal component analysis

2-amino-1-methyl-6-phenylimidazole [4,5-b] pyridine (PhIP) is one of the higher levels of HAAs produced in protein foods during heating. The effects of heating temperature, time, and concentration of precursors on PhIP and related substances in the chemical model system and roast pork patty were studied using HPLC-Q-Orbitrap-HRMS and GC-MS. Results showed that the heating temperature, time, and concentration of four precursors significantly affected PhIP and its related substances (P < 0.05) in the chemical model system. Among them, PhIP production was greatest when heating at 200 min with 220 °C, and the concentrations of phenylalanine, creatinine, glucose, and creatine added were 10, 20, 20, and 20 mmol/L, respectively. Moreover, as the fat proportion of roast pork patties increased, PhIP and its intermediate-phenylacetaldehyde concentrations increased substantially (P < 0.05). PCA results showed that the samples of PhIP and related substances gradually dispersed as the temperature and time increased, and there were obvious effects among them.

Effect of acrolein on the formation of harman and norharman in chemical models and roast beef patties

Harman and norharman were the most abundant β-carboline-type heterocyclic amines (HCAs) detected in various foodstuffs. Unsaturated fatty acids in foods may undergo rapid oxidative deterioration during transportation, storage and heat treatment, forming reactive carbonyl species (RCS). This work studied the effects of acrolein, a highly reactive RCS, on the formation of harman and norharman in the tryptophan model system. Results showed that 0.005, 0.01, 0.015, 0.02, 0.05, 0.1 and 0.2 mmol of acrolein led to harman production increased by 528 %, 752 %, 981 %, 1172 %, 1375 %, 1288 % and 768 % respectively, and led to norharman formation increased by 116 %, 129 %, 152 %, 169 %, and 197 %, 185 % and 157 %, respectively. Furthermore, acrolein addition reduced the residue of tryptophan (up to 63.19 %), but increased the level of the intermediates including formaldehyde (up to 352 %), acetaldehyde (up to 491 %), (1S,3S)-1-Methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (MTCA, up to 1936 %), and 1,2,3,4-tetrahydro-β-carboline-3-carboxylicacid (THCA, up to 2142 %) in the tryptophan model system. Acrolein might react with tryptophan, harman and norharman to eliminate them directly. These data suggested that acrolein may contribute to harman and norharman formation through participating in the above complex chemical reactions. In addition, the content of harman and norharman produced in roast beef patties made of minced beef oxidized for 2, 4, 6, 8, and 10 days increased by 118 %, 188 %, 267 %, 137 %, and 48 %, respectively, and led to norharman formation increased by 140 %, 132 %, 90 %, 86 %, and 74 %, respectively compared with those made of fresh minced beef, which further illustrated that lipid oxidation products potentially contributed to harman and norharman formation.

Effect of acrolein, a lipid oxidation product, on the formation of the heterocyclic aromatic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in model systems and roasted tilapia fish patties

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Acrolein was able to contribute to PhIP formation.

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Acrolein facilitated Strecker degradation of phenylalanine.

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Acrolein increased the formation of some key intermediates of PhIP.

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Acrolein reacted with phenylalanine, creatinine, and PhIP to form adducts.

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The oxidation of tilapia fish increased the PhIP formation in the roasted fish patties.

The effect of acrolein on the formation of the 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was investigated in a chemical model. Acrolein was found to increase PhIP formation at each tested addition level. 0–0.2 mmol of acrolein increased PhIP formation dose-dependently, while high levels of acrolein (>0.2 mmol) did not further increase PhIP formation. Mechanistic study showed that acrolein addition decreased the residue of phenylalanine and creatinine, but increased the content of some key intermediates. Further analysis indicated that acrolein can react with phenylalanine, creatinine, and PhIP to form adducts. These results suggested that acrolein was able to contribute to PhIP formation as a consequence of its comprehensive ability to facilitate Strecker degradation of phenylalanine and react with phenylalanine, creatinine, and PhIP. In addition, oxidation of the tilapia fish increased the PhIP formation in the roasted fish patties, further supporting the potential contribution role of lipid oxidation products to the formation of PhIP.

Effect of Acrolein, a Lipid Oxidation Product, on the Formation of the Heterocyclic Aromatic Amine 2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) in Model Systems and Roast Salmon Patties

The effect of acrolein, a lipid oxidation product, on the formation of the heterocyclic aromatic amine 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) was investigated in a chemical model containing glycine, creatinine, and glucose. Acrolein addition at 0.02-0.2 mmol increased MeIQx formation, while high levels of acrolein (>0.2 mmol) did not further increase MeIQx formation. Moreover, acrolein addition decreased the residue of glycine and creatinine but increased the residue of glucose; it also increased the formation of volatile intermediates in the MeIQx-producing chemical model. Further analysis indicated that acrolein can react with glycine, creatinine, and MeIQx to eliminate them. These results revealed that acrolein was able to contribute to MeIQx formation as a consequence of the comprehensive ability of acrolein to facilitate Strecker degradation of glycine, increase the formation of volatile intermediates, and react with glycine, creatinine, and MeIQx. In addition, the oxidation of minced salmon increased the content of MeIQx in the roasted salmon patties, further supporting the potential contribution role of lipid oxidation products in the formation of MeIQx.

Effects of the Deacetylation Degree of Chitosan on 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) Formation in Chemical Models and Beef Patties

The effects of the deacetylation degree (DD) of chitosan on heterocyclic aromatic amine formation were investigated in chemical models and beef patties. The results in model systems showed that at lower addition levels (10 mg), chitosan with 85% DD showed the strongest inhibitory effect against 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) formation, while chitosan with a higher DD (95%) or a lower DD (72 and 50%) did not show any significantly inhibitory effect. Further mechanism study showed that chitosan addition reduced the content of Maillard reaction intermediates including phenylacetaldehyde and the aldol condensation product but increased the PhIP precursor creatinine residue in the chemical model, indicating that chitosan at least partially competed with creatinine to react with phenylacetaldehyde to inhibit PhIP formation. In roast beef patties, 0.15% (w/w) chitosan (85% DD) significantly reduced the formation of PhIP, MeIQx, 4,8-DiMeIQx, Harman, and Norharman by 56.21, 33.32, 31.35, 25.14, and 28.12%, respectively. Moreover, chitosan significantly inhibited the formation of aldehydes in roast beef patties, further confirming the above-mentioned inhibition mechanism. However, the addition of chitosan might promote fatty acid oxidation. In addition, chitosan addition below 0.15% (w/w) had no significant effect on the textural properties of the roast samples.

Puerarin inhibited 3-chloropropane-1,2-diol fatty acid esters formation by reacting with glycidol and glycidyl esters

The inhibitory effects of seven polyphenols on 3-chloropropane-1,2-diol fatty acid esters (3-MCPDE) formation were investigated in palm oil models. Results showed that there was not a positive significant correlation between the free-radical scavenging activities of the tested compounds and their 3-MCPDE-formation inhibitory activities; puerarin, with weak antioxidant activity, showed the highest inhibitory capacity. Moreover, puerarin reduced the content of glycidol and glycidyl esters (GEs), two key intermediates of 3-MCPDE formation in the oil models; and a puerarin-adduct was discovered in the oil fortified with glycidol or GEs, with its structure elucidated by LC-MS/MS and comparison with newly synthesized ones. Based on its chemical structure, we proposed that puerarin, at least in part, reacted with glycidol and GEs to inhibit 3-MCPDE formation. In addition, the formed compound, puerarin-7-O-propanediol was identified in the potato chips frying system, further confirming reacting with glycidol/GEs as a key mechanism of puerarin to inhibit 3-MCPDE formation.

Inhibitory effect of selected hydrocolloids on 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP) formation in chemical models and beef patties

2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a mutagen and a rodent carcinogen mainly formed in thermally processed muscle foods. Hydrocolloids are widely used as thickeners, gelling agents and stabilizers to improve food quality in the food industry. In this study, the inhibitory effects of eight hydrocolloids on the formation of PhIP were investigated in both chemical models and beef patties. 1% (w/w) of carboxymethylcellulose V, κ-carrageenan, alginic acid, and pectin significantly reduced PhIP formation by 53 %, 54 %, 48 %, and 47 %, respectively in chemical models. In fried beef patties, κ-carrageenan appeared to be most capable of inhibiting PhIP formation among the eight tested hydrocolloids. 1% (w/w) of κ-carrageenan caused a decreased formation of PhIP by 90 %. 1% (w/w) of κ-carrageenan also significantly reduced the formation of other heterocyclic aromatic amines including MeIQx and 4,8-DiMeIQx by 64 % and 48 %, respectively in fried beef patties. Further mechanism study showed that κ-carrageenan addition decreased the PhIP precursor creatinine residue and reduced the content of Maillard reaction intermediates including phenylacetaldehyde and aldol condensation product in the chemical model. κ-Carrageenan may inhibit PhIP formation via trapping both creatinine and phenylacetaldehyde. The structures of adducts formed between κ-carrageenan and creatinine and κ-carrageenan and phenylacetaldehyde merits further study.

Isorhamnetin and Hispidulin from Tamarix ramosissima Inhibit 2-Amino-1-Methyl-6-Phenylimidazo[4,5-b]Pyridine (PhIP) Formation by Trapping Phenylacetaldehyde as a Key Mechanism

Tamarix has been widely used as barbecue skewers to obtain a good taste and a unique flavor of roast lamb in China. Many flavonoids have been identified from Tamarix, which is an important strategy employed to reduce the formation of heterocyclic amines (HAs) in roast meat. Isorhamnetin, hispidulin, and cirsimaritin from Tamarix ramosissima bark extract (TRE) effectively inhibit the formation of 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (PhIP), the most abundant HAs in foods, both in roast lamb patties and in chemical models. According to the results of the GC-MS analysis, TRE and the three flavonoids significantly reduced the contents of phenylacetaldehyde, an important intermediate involved in PhIP formation at three levels. A subsequent ultra performance liquid chromatography-mass spectrometry (UPLC-MS) analysis revealed that these flavonoids trapped phenylacetaldehyde by forming interaction adducts. The formation of three postulated adducts, 8-C-(E-phenylethenyl)isorhamnetin, 6-C-(E-phenylethenyl)isorhamnetin and 8-C-(E-phenylethenyl)hispidulin, in the chemical models and roast lamb patties was further confirmed by a TOF-MS/MS analysis. Our results demonstrate that TRE and the corresponding flavonoids trap phenylacetaldehyde to form adducts and thus inhibit PhIP formation, suggesting their great potential beneficial effects on human health.

Thermal processing food-related toxicants: a review

Heterocyclic aromatic amines, acrylamide, 5-hydroxymethylfurfural, furan, polycyclic aromatic hydrocarbons, nitrosamines, acrolein, chloropropanols and chloroesters are generated toxicants formed in some foodstuffs, mainly starchy and protein-rich food during thermal treatment such as frying, roasting and baking. The formation of these chemical compounds is associated with development of aromas, colors and flavors. One of the challenges facing the food industry today is to minimize these toxicants without adversely affecting the positive attributes of thermal processing. To achieve this objective, it is essential to have a detailed understanding of the mechanism of formation of these toxicants in processed foods. All reviewed toxicants in that paper are classified as probable, possible or potential human carcinogens and have been proven to be carcinogenic in animal studies. The purpose of that review is to summarize some of the most frequent occurring heat-generated food toxicants during conventional heating, their metabolism and carcinogenicity. Moreover, conventional and microwave heating were also compared as two different heat treatment methods, especially how they change food chemical composition and which thermal food toxicants are formed during specific method.