| Advanced glycation end products(AGEs)are a group of stable end products produced by a series of reactions between free amino groups and carbonyl groups under non-enzymatic conditions,which may cause many chronic diseases.There are more than 40AGEs have been successfully identified,and N~ε-carboxymethyllysine(CML)is the most representative type of AGEs.During the processing and storage,the AGEs are formed in meat.There are many reports about the change of AGEs contents during processing.However,there are few studies on the formation of AGEs during meat storage.In this study,the effects of aging time on the CML content in raw/cooked white feather broilers and yellow feather broilers meat were firstly investigated.Then combined with the changes of meat quality indexes,oxidation degree and precursor substance content,the effects of aging time on CML in raw/boiled broilers were explained.Finally,using myofibrillar protein-glucose as glycosylation model system,the effect mechanism of aging time on CML in cooked broiler meat was analyzed from the perspective of protein.The detailed contents and results are shown as follows:1.Effects of aging time on AGEs contents in white and yellow feather broilers meatBreast and leg meat of white and yellow feather broilers were aged for 0-168 h at 4℃.The CML contents in raw and cooked(100℃,30 min)broilers meat during different aging time were investigated.With the aging time increasing,CML content in raw white feather broiler breast meat had no significant change,while that in cooked breast meat significantly increased during 0-6 h,then decreased during 6-24 h,finally increased again.And with the aging time prolonging,CML content in raw/cooked leg meat had no significant change during 0-24 h,then increased significantly.But aging time had no significant effect on the CML contents in raw/cooked yellow feather broilers meat.Meanwhile,CML contents in white feather broilers meat were much higher than that in yellow feather broilers meat.Thus,white feather broilers can be selected as the research object to study the mechanism of storage time on CML content in the broiler meat in the future.2.Effects of changes in meat quality,oxidation degree and precursor substancecontent during aging on AGEs contents in broiler meatBreast and leg meat of white feather broilers were aged for 0–7 d at 4℃.The broilers meat quality(cooking loss,drip loss,shear force,non-protein nitrogen and myofibrillar fragmentation index),the degree of oxidation(fat oxidation and protein oxidation),CML precursor substances content(lysine(Lys),glyoxal(GO)and schiff base)and the content of CML during aging were investigated.The changes of CML in cooked broilers meat(100℃,30 min)after aging were also studied.Finally,Pearson correlation analysis of CML with oxidation indexes and precursors was carried out.The results showed that during aging,the water-holding capacity of broilers meat were significantly increased firstly(p<0.05),significantly decreased(p<0.05),and finally significantly increased at 1-7 d(p<0.05);The shear force of broilers meat increased firstly and reached the highest value at 6 h(p<0.05),significantly decreased(p<0.05);The non-protein nitrogen,myofibrillar protein fragmentation index,TBARs and carbonyl groups of broilers breast and leg meat were significantly increased(p<0.05);The contents of GO and Schiff base in broilers breast meat were firstly increased significantly(p<0.05),significantly decreased(p<0.05),and finally increased again,while the content of broilers leg meat showed a significant increasing trend(p<0.05).As aging time increased,the CML content in cooked broiler breast meat significantly increased from 1.81 to 2.00 mg/kg during 0-6 h,and then decreased from 2.00 to 1.80 mg/kg during 6 h-1 d,finally increased again during 1-7 d,while the CML contents of raw and cooked leg meat significantly and continuously increased from 1.78 to 2.08 mg/kg.Furthermore,CML was extremely positively correlated with fat oxidation(R~2=0.793,p<0.01),protein oxidation(R~2=0.917,p<0.01)and GO(R~2=0.678,p<0.05),and was negatively correlated with Lys(R~2=0.536,p<0.05).No significant correlation was observed between Schiff base and CML.3.Effects of chicken myofibrillar protein at different aging times on AGEsformation in glycosylation simulation systemBreast and leg meat of white feather broilers were aged for 0–7 d at 4℃.The changes of solubility,turbidity,surface hydrophobicity,particle size,carbonyl group,sulfhydryl group,secondary structure and protein bands in SDS-PAGE of myofibrillar protein of white feather broilers meat during storage were investigated.Then,the extracted myofibrillar protein was mixed with glucose,and glycation reaction was carried out at 100℃to detect the CML content of the mixed solution.Pearson correlation analysis was made between CML and the above indexes.During aging,the solubility of myofibrillar protein in breast and leg meat decreased significantly at 0-6 h(p<0.05),significantly increased at 6 h-7 d(p<0.05),while the results of turbidity were just the opposite;The carbonyl group andβ-folding of myofibrillar protein in breast and leg meat were significantly increased(p<0.05),while total sulfhydryl group,active sulfhydryl group andα-helix showed a decreasing trend(p<0.05);The particle size of myofibrillar protein of breast and leg meat and the surface hydrophobicity of myofibrillar protein of breast meat were significantly increased at 0-6 h(p<0.05),significantly decreased at 6 h-3 d(p<0.05),but the surface hydrophobicity of broiler leg myofibrillar protein was significantly increased at 0-6 h(p<0.05),and then decreased.With aging time increasing,the CML content of breast meat myofibrillar protein after glycosylation increased firstly,then decreased,and finally increased again,while the CML content of leg meat myofibrillar protein after glycosylation increased significantly(p<0.05).In addition,CML was positively correlated with turbidity,carbonyl group andβ-folding(p<0.05),had a very significant positive correlation with the α-helix(p<0.01). |
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