Oxidation Law Of Beef Lipid And Protein Under Roasting Conditions And The Effect Of Advanced Glycation End Products On The Health Of Mice

Beef is one of the representative red meat with high protein content and low fat content.It contains 8 kinds of amino acids necessary for human growth and development.Almost all of them can be digested,absorbed and utilized by human body after ingestion.It is a good dietary source for human beings to obtain high-quality protein,essential amino acids,vitamins and minerals.The heat treatment of beef is an important processing link before eating,but the high temperature environment in the heat treatment process may destroy the tissue structure of beef,cause the loss of nutrients,and even produce some substances that have adverse effects on human health.Therefore,reasonable control of heat treatment conditions,such as temperature and time,is of great significance to ensure the edible quality and nutritional value of beef.Roasting is a representative high-temperature heat treatment method,which uses air as the heat transfer medium to heat food.In the process of high-temperature roasting,some harmful substances will be produced,such as heterocyclic amines(HAA),polycyclic aromatic hydrocarbons(PAHs),acrylamide,etc.,which will do varying degrees of harm to human body.Therefore,it is very important to reasonably control the roasting temperature and time.Taking beef as the research object,this study studied the effect of different roasting temperature and time on beef lipid and protein oxidation,nutrient changes and the production of harmful products,and evaluated the mechanism of advanced glycation end products(AGEs),one of the harmful products,on blood glucose,blood lipid and renal function through mouse experiments.1.The effect of different roasting temperatures(150?,190?,230?,270?,310?)on lipid and protein oxidation of beef were studied.Raw beef was used as a control,and the color,peroxide value(PV),thiobarbituric acid reactive substance(TBARS),sulfhydryl and carbonyl content,protein solubility,tryptophan and schiff base content,protein molecular weight distribution and amino acid residue side chain modification of beef were measured to discuss the effect of different roasting temperatures on beef lipid and protein oxidation.The results show that with the increase of temperature,L*value and b*value increased,and a*value decreased.The values of lipid oxidation indexes PV and TBARS,schiff base and carbonyl content also increased,while the content of sulfhydryl group and protein solubility decreased significantly(p<0.05).The results showed that the band of myosin heavy chain was degraded by sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE),and the actin band was still clearly visible.The result of ultra high performance liquid chromatography tandem mass spectrometry(UPLC-MS/MS)showed that the aromatic amino acid residues in all samples were oxidized to varying degrees,and lysine residues were formed ?-Aminoadipic acid semialdehyde(AAS)??-Aminoadipic acid(AAA)and AGEs,such as carboxymethyl lysine(CML)and carboxyethyl lysine(CEL).Some modified products were only present in the roasted samples,such as AAA,CEL and malondialdehyde(MDA).Lipid protein oxidation is closely related to color parameters during roasting.At higher temperatures,protein and lipid oxidation intensifies.The amino acid side chain was also modified at high temperature,especially in aromatic amino acid residues.2.The effect of different roasting temperatures(150?,190?,230?,270?,310?)for 20 min and 190? for different roasting times(10 min,20 min,30 min)on the content of nutrients(moisture,fat,protein,ash)and the formation of harmful products(nitrite,volatile base total nitrogen,AGEs,PAHs)in beef were studied.The results showed that the moisture content of beef decreased with the increase of roasting temperature and time,resulting in the increase of the relative content of fat,protein and ash.At the same time,the content of nitrite and volatile base total nitrogen also increased continuously.The change of nitrite and volatile base total nitrogen were not significant when roasting at 150-230? for 20 min(p>0.05),and there was no significant difference in volatile base total nitrogen content when roasted at 190? for 20-30 min(p>0.05).Roasting temperature and time have great effects on AGEs and their precursors in beef,such as glyoxal,methylglyoxal,pentosin,fluorescent AGEs and so on.Compared with the control group,the content of glyoxal in beef decreasea,while the content of methylglyoxal,pentosin and fluorescent AGEs increased.The content of glyoxal decreased with the increase of roasting temperature and time,but increased at 190-310?.On the contrary,the content of methylglyoxal,pentosin and fluorescent AGEs in beef increased significantly(p<0.05),indicating the continuous accumulation of AGEs in beef.A total of 13 PAHs were identified by gas chromatography-mass spectrometry(GC-MS).The content of 13 PAHs in beef increased with the increase of roasting temperature and time.Among them,benzo(k)pyrene and benzo(a)pyrene,which are the most carcinogenic to human body,were 0.36 ?g/kg in raw meat and 0.35 ?g/kg,which was doubled by high temperature and long-time roasting.After beef was roasted at 270? and 310? for 20 min,the content of benzo(k)pyrene increased to 9.49 ?g/kg and 5.66 ?g/kg,the content of benzo(a)pyrene increased to 5.45 ?g/kg and 4.42 ?g/kg.After roasting at 190?for 30 min and 40 min,the content of benzo(k)pyrene increased to 4.81 ?g/kg and 24.20 ?g/kg,benzo(a)pyrene content increased to 3.85 ?g/kg and 17.79 ?g/kg.In addition,Indo(1,2,3-cd)pyrene was detected only in samples roasted at 230?,270?,310? for 20 min and 190? for 40 min.3.The effect of AGEs intake on blood glucose,blood lipid,the contents of serum CML and CEL,the indexe of oxidative stress in serum and kidney,urinary protein,urea nitrogen,and the content of fluorescent ages in serum and kidney were studied to evaluate the mechanism of ages intake on blood glucose,blood lipid and oxidative stress in mice.The results showed that the increase of AGEs intake caused the increase of blood glucose and blood lipid levels,including the increase of serum glucose,total cholesterol,triglycerides,low-density lipoprotein cholesterol and high-density lipoprotein cholesterol.The indexe of blood glucose and blood lipid in high-dose HA group were significantly higher than those in control NC group(p<0.05).With the increase of intake,AGEs accumulated continuously in serum and kidney of mice,the content of fluorescent ages in serum and kidney increased,and the contents of CML and CEL in serum increased significantly compared with NC group(p<0.05).At the same time,excessive intake of ages led to renal hypertrophy,a significant increase in renal coefficient(p<0.05),an increase in MDA content in serum and kidney,a decrease in superoxide dismutase activity and glutathione peroxidase content,resulting in an increase in the level of oxidative stress.The renal function of mice was gradually impaired with the increase of ages intake.The 24 h urine volume decreased significantly(p<0.05),the content of urinary protein increased significantly(p<0.05),the concentration of urinary creatinine and blood creatinine increased,and the creatinine clearance rate was reduced.The results of renal HE staining sections showed that excessive intake of AGEs for a long time would cause renal structural damage and inflammatory cell infiltration.