Formation of a creatinine thermal degradation product and its role and participation in the radical pathway of forming the pyridine ring of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (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.

Inhibitory effects of cassiae semen extract on the formation of 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP) in model system

Introduction

2-Amino-1-methyl-6-phenylimidazole [4,5-b] pyridine (PhIP), a heterocyclic amine (HAA), is found in meat products heated at high temperatures. However, PhIP is a mutagenic and potential carcinogenic compound. Cassiae semen, a type of medicine and food homology plant, is abundant in China and has been less applied for inhibiting heterocyclic amines.

Methods

To investigate the inhibitory effect of cassiae semen extract on PhIP formation within a model system and elucidate the inhibitory mechanism, an ultrasonic-assisted method with 70% ethanol was used to obtain cassiae semen extract, which was added to a model system (0.6 mmol of phenylalanine: creatinine, 1:1). PhIP was analyzed by LC-MS to determine inhibitory effect. The byproducts of the system and the mechanism of PhIP inhibition were verified by adding the extract to a model mixture of phenylacetaldehyde, phenylacetaldehyde and creatinine.

Results

The results indicated that PhIP production decreased as the concentration of cassiae semen extract increased, and the highest inhibition rate was 91.9%. Byproduct (E), with a mass-charge ratio of m/z 199.9, was detected in the phenylalanine and creatinine model system but was not detected in the other systems. The cassiae semen extract may have reacted with phenylalanine to produce byproduct (E), which prevented the degradation of phenylalanine by the Strecker reaction to produce phenylacetaldehyde.

Discussion

Cassiae semen extract consumed phenylalanine, which is the precursor for PhIP, thus inhibiting the formation of phenylacetaldehyde and ultimately inhibiting PhIP formation. The main objective of this study was to elucidate the mechanism by which cassiae semen inhibit PhIP formation and establish a theoretical and scientific foundation for practical control measures.

Release mechanism between sarcoplasmic protein-bound and free heterocyclic amines and the effects of dietary additives using an in-vitro digestion model

In this study, the release mechanism between free and sarcoplasmic protein-bound heterocyclic amines (HAs) in an in-vitro digestion model were investigated by comparing changes in the amount of HAs between groups with different enzyme dosages and at different digestion stages. The effects of the addition of onions, peppers, and apples on the release mechanism were also studied. We found that bound HAs cannot be completely converted to free HAs under normal enzyme dosages and that a significant increase in HAs occurred in the intestines. The release rate of bound HAs was 5.99%-43.84%, and the total release rate of HAs was 36.67%. Furthermore, the release rate of β-carbolines was the highest (34.41%-43.84%). The addition of onions, peppers, and apples significantly increased the number of free HAs, with growth rates reaching 56.06%, 43.43%, and 54.44%, respectively. These additives mainly promoted the generation of free harman and norharman.

Effects of the non-covalent interactions between polyphenols and proteins on the formations of the heterocyclic amines in dry heated soybean protein isolate

Soybean proteins are the main component of plant-based meat alternatives in the Chinese market. The effects of non-covalent interactions between polyphenols and proteins on the protein structures, the rest physicochemical properties, and formations of heterocyclic amines (HAs) were examined using a polyphenols-containing soybean protein isolate (SPI) complex as a model to dry heating at 170℃ for 10 min. The results showed that tetrahydro-curcumin had extensive inhibitory effects on the HA formation. In addition, tea polyphenols, grapeseed procyanidins, and dihydromyricetin were also found to have inhibitory effects only on some HAs. Correlation analysis showed that polyphenols altered the secondary structure and steric structure of the protein by interacting with the protein, which affects the HA formation. The results provided theoretical references and a basis for the formation mechanisms of HAs in polyphenol-inhibiting protein foods.

The inhibitory effects of yellow mustard (Brassica juncea) and its characteristic pungent ingredient allyl isothiocyanate (AITC) on PhIP formation: Focused on the inhibitory pathways of AITC

The effects of yellow mustard (Brassica juncea) and its characteristic component allyl isothiocyanate (AITC) on the formation of 2-amino-y1-methyl-6-phenylimidazo[4,5-b] pyridine (PhIP) in roast beef patties and PhIP-producing model systems were investigated. The probable inhibitory pathways of AITC on PhIP formation were also investigated in the model systems. The results revealed that yellow mustard and AITC can reduce PhIP in roast beef patties up to 41.7% and 60.2%, respectively. The rate of inhibition of PhIP also reached 64.8% in the PhIP-producing model systems. Furthermore, AITC could react with creatinine and phenylalanine in the model system (reducing each by 15.0%%-23.7% and 31.4%-55.8%, respectively). AITC showed the great scavenging ability of free radical scavenging (up to 64.2%). AITC also reacted with the intermediate phenylacetaldehyde (16.9%-30.8%) and the final product PhIP (7.0%-24.6%). It is speculated that AITC can inhibit PhIP through competitive inhibition of precursors, blocking intermediate, free radical scavenging, and direct elimination of PhIP.

Identification of acrolein as the reactive carbonyl responsible for the formation of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx)

Reaction mixtures of reactive carbonyls and creatinine were submitted to high temperature and studied to identify the reactive carbonyl(s) responsible for 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) formation. MeIQx was produced by reaction of acrolein and creatinine within a wide pH range and with an activation energy of 81.1 ± 1.4 kJ/mol. No additional reactants were required, although methylglyoxal, ammonia, and formaldehyde also participated in the reaction. Nevertheless, these additional reactants were produced in situ from either acrolein or creatinine. A reaction pathway that both explains the formation of MeIQx and is valid for the formation of other heterocyclic aromatic amines (HAAs) with the structure of quinoxaline is proposed. Obtained results demonstrate the key role of reactive carbonyls present in foods (the food carbonylome) on HAA formation. Because creatinine is ubiquitous in proteinaceous foods, the control of the food carbonylome seems to be the key point to control HAA formation in foods.