Effects Of Several Physical Processing Methods On The Dissociation Effect Of Neu5Gc In Red Meat

In October 2016,the International Agency for Research on Cancer listed red meat as a Class 2A carcinogen.N-glycolylneuraminic acid(Neu5Gc)has attracted the attention of researchers as a risk substance for red meat.Neu5 Gc is a sialic acid,although most of the deuterostome can synthesize Neu5 Gc in vivo,but due to mutations in the cytosine monophosphate-N-acetylneurami-nic hydroxylase(CMAH)gene in humans,the human body cannot Synthesis of Neu5 Gc.No other route was found to synthesize Neu5 Gc in humans.However,Neu5 Gc is still present in the epithelial and endothelial cell surface of the human body,especially in some cancer tissues,including colon cancer,breast cancer,melanoma and retinoblastoma.The intake of foods rich in Nue5 Gc such as red meat is the only source of Neu5 Gc in the human body.Studies have shown that the intake of Neu5 Gc can cause the body to produce "xenoautoantigen",triggering an inflammatory response,thereby promoting the occurrence of various cancers,atherosclerosis,type 2 diabetes and other diseases.Therefore,it is urgent to find a safe and effective way to reduce the content of Neu5 Gc in red meat.In this paper,the effects of several physical processing methods on the content of Nue5 Gc in red meat were discussed.The mechanism of the reduction was studied by LC-MS and density functional method.The changes of Neu5 Gc molecular structure was simulated under external electric field.(1)Screening of physical processing methods for effectively reducing the content of Neu5 Gc in red meatRed meat was treated by three thermal processing methods(microwave,high temperature and pressure and electrical stimulation)and two non-thermal processing methods(pulsed light and ultra high pressure).The experimental results showed that the three thermal processing methods can effectively reduce the content of Nue5 Gc in red meat.In the non-thermal processing mode,the pulsed light can reduce the content of Neu5 Gc in red meat after reaching 30 min.The highest reduction rate of eachmethod was compared,and the order of decreasing effect from high to low was:electrical stimulation > high temperature and pressure > microwave > pulsed light,which were reduced by 74.24%,62.17%,33.37% and 22.14%,respectively.The treatment conditions are: electric stimulation of red meat for 50 s under the voltage of120V;treatment of red meat for 20 min under high temperature and pressure at 125°C and 160KPa;microwave treatment of red meat for 50 s at 60% rated power;pulse light duration 30 min.(2)Study on the mechanism of reducing the content of Neu5 Gc in red meat by various physical processing methodsIn order to explore the mechanism of the above physical processing methods to reduce the content of Neu5 Gc in red meat,the Neu5 Gc standard was treated separately.The experimental results show that electrical stimulation and high temperature and pressure can effectively reduce the content of Neu5 Gc standard,indicating that electrical stimulation and high temperature and pressure can directly destroy Neu5 Gc molecules.The Neu5 Gc standard after electrical stimulation and high temperature and pressure treatment was detected by LC-MS.According to the results of mass spectrometry combined with DFT M062X/def2 TZVP,it is speculated that there are four possible cleavage paths for Nue5 Gc.In order to explore the mechanism of microwave and pulsed light reducing the content of Neu5 Gc in red meat,the effects of these two methods on the free and bound Neu5 Gc content in red meat were tested.The experimental results show that pulsed light can effectively reduce red the content of Neu5 Gc in the bound state in red meat.Although the microwave treatment has no effect on the Neu5 Gc standard,on the basis of red meat as the matrix,microwave treatment can reduce the content of bound and free Neu5 Gc in red meat.(3)Effect of external electric field on the structural properties of Neu5 Gc moleculeThe optimized geometry of Neu5 Gc was obtained using the M062 X method.Density functional theory was used to investigate the changes in the molecular structure parameters of Neu5 Gc under external electric field.As the electric fieldstrength increased,the Hamiltonian of the molecule increased gradually,the total energy showed an increasing trend,resulting in a decreased in molecular structure stability;the energy gap value always showed a decreasing trend,which indicated that the molecular reactivity was gradually increased.The dehydrogenation and dissociation energies of different parts under the external field were smaller than those without electric field,which indicated that the external electric field can reduce the dissociation energy of molecules.When considered the solvent effect of water environment,the difference of dehydrogenation dissociation energy under external electric field was quite different,indicated that the aqueous solution had a significant influence on the dissociation of molecules under external electric field.Under the action of external electric field,the distance of hydroxyl oxygen in the Neu5 Gc molecule,the bond length of the C-O bond connected to the hydroxyl group,the activity index,the natural charge distribution,and the intramolecular hydrogen bond had different degrees of change.The above experimental results showed that under the external electric field,Neu5 Gc molecule had higher reactivity,lower molecular stability and was prone to cleavage.Further,a strong theoretical basis for the electrical stimulation can effectively reduce the content of Neu5 Gc in red meat.