Research On The Differences In Quality Characteristics And Multi-omics Analysis Of Bactrian Camel Meat From Different Ages And Different Muscle Parts

Bactrian camels adapt to harsh environments such as cold,heat,and high radiation in arid and semi-arid regions in China.The cultivation and product processing of camels have always been an important economic source for herdsmen in the Gobi Desert region of China.Recently,with the increase in consumption of meat products,high nutrition and high-quality meat products have received widespread attention.Camel meat is considered to be suitable for human consumption because of its high protein,low fat,and low cholesterol characteristics.Moreover,it is a good source of essential amino acids and essential fatty acids.However,the current research on the quality characteristics of camel meat is not systematic and in-depth,the selection of the optimal slaughter age and the value of high-quality muscle part meat have not been reflected.Especially,the unique nutritional functions of camel meat have not been fully exploited,resulting in low economic benefits for camel meat,seriously restricting the development of characteristic animal husbandry in desert areas of China.This research selected Alxa Bactrian camel meat as experimental material to analyze the nutritional composition and edible quality characteristics of camel meat from three different age groups(3～4year old,6～7year old,9～10year old;represented by I,II,and III,respectively)and three different muscle part groups(longissimus dorsi,Psoas Major,Semitendinosus;represented by W,L,and X,respectively),to explore the effect of age and muscle part on the chemical composition and quality characteristics of Bactrian camel meat.Simultaneously,proteomics and metabolomics were performed to study the differences in the expression of proteins and metabolites in camel meat,revealing the internal mechanism of meat quality changes in camel meat from different ages and different muscle parts.In addition,the important proteins,metabolites,and metabolic pathways that affect muscle quality changes were emphatically analyzed.This study provided a scientific basis for the selection of the optimal slaughter age for camels and the development of high-quality camel meat products.The main research results are as follows:1.The result showed that the nutritional quality,color quality and tenderness quality of camel meat from different ages and different muscle parts were different.The protein and fat content in camel meat increased significantly with age(P<0.05),while the water content decreased significantly(P<0.05).The ratio of essential and total amino acids(EAA/TAA)in camel meat was 39.61%～39.97%,and the ratio of essential and non-essential amino acids(EAA/NEAA)was 65.59%～66.58%,indicating that the protein of camel meat conforms to the ideal protein standard model proposed by FAO/WHO.The polyunsaturated fatty acid(PUFA),the ratio of saturated fatty acid to unsaturated fat acid(UFA/SFA),n-6/n-3,n-6,n-3 in group I were significantly higher than those in group III;the content of saturated fatty acids in group W was significantly higher than that in group X and L(P<0.05),while the content of unsaturated fatty acids(MUFA and PUFA)in group X was higher than that in group W and L(P<0.05).Mineral elements such as potassium,phosphorus,iron,selenium,and copper were significantly affected by age(P<0.05),while the effect of muscle part was not significant(P>0.05).Age had significant effects on meat tenderness,cooking loss,and color(P<0.05).With the increase of age,the sarcomere length of myofibril ultrastructure became shorter,the shear force increased,and the palatability decreased;meanwhile,the brightness and cooking loss decreased,resulting in a decrease in juiciness and a darker color of the meat.2.The result showed that the differential expression of proteins had an important effect on meat quality of camel meat from different ages and different muscle parts.A total of 311 differentially expressed proteins(DEPs)were identified in three age groups.The number of DEPs was 245 in the I vs II comparison group,16 in the II vs III comparison group,and 139 in the I vs III comparison group.194,1,and 110 DEPs were up-regulated,where as 51,15,and 29 DEPs were down-regulated.GO functional annotation analysis indicated that structural proteins,metabolic proteins,and heat stress proteins could be used as biomarkers for different ages of camel meat.KEGG pathway analysis showed that DEPs were mainly involved in fatty acid metabolism,glycolysis/glucose production,amino acid biosynthesis,and HIF-1 signaling pathway.PPI analysis shows that metabolic enzyme proteins were key network connecting proteins that affect camel meat of different ages.Correlation analysis between DEPs and quality traits of camel meat showed that there were 16 DEPs with significant correlation were correlated closely with tenderness quality.The tenderness of camel meat from three age groups was mainly influenced by actin,histone and protein kinases.In addition,a total of 552 differentially expressed proteins(DEPs)were identified in three muscle parts.The number of DEPs was 141 in the L vs W comparison group,436 in the W vs X comparison group,and 196 in the L vs X comparison group.102,190,and 128 DEPs were up-regulated,where as 39,246,and 68 DEPs were downregulated.GO functional annotation analysis indicated that heat stress proteins and metabolic enzyme proteins could be used as marker proteins for different parts of camel meat.The significantly different pathways for the DEPs mainly included Oxidative phosphorylation,glycolytic metabolism,and amino acid synthesis and metabolism.PPI analysis revealed that proteins such as NADH oxidoreductase and laminin were key network connecting proteins that affect meat quality.Correlation analysis showed that 17 DEPs were significantly correlated with tenderness quality;3 DEPs were significantly correlated with p H value,and 11 DEPs were significantly correlated with meat brightness.3.The results showed that the differential expression of metabolites(DEMs)also had an important impact on the meat quality of camel meat from different ages and different muscle parts.The number of DEMs was 78 in the I vs II comparison group,49 in the II vs III comparison group,and 65 in the I vs III comparison group.The content of polyunsaturated fatty acids(especially n-6 PUFA and n-3 PUFA)and the PUFA/UFA ratio in group I were significantly higher than those in group III,which was mainly related to the significant upregulation of arachidonic acid,linoleic acid,and 13-L-hydroperoxide oleic acid concentrations in related metabolic pathways.L-leucine,L-valine,L-glutamine,etc.could be used as biomarker metabolites for different ages of camel meat.The DEMs in different age groups are mainly enriched in significantly different pathways such as protein,amino acids,fatty acids,vitamin and mineral metabolism,indicating that the digestion and metabolism of various nutrients in camels at different age stages are different.In the comparison of metabolites in the three muscle parts,the DEMs were 62 in the L vs W comparison group,79 in the W vs X comparison group,and 69 in the L vs X comparison group,respectively.L-isoleucine,L-phenylalanine,L-tryptophan,etc.could be used as biomarker metabolites for different muscle parts.The DEMs in different part groups are mainly enriched in significantly different pathways such as amino acid biosynthesis,protein digestion and absorption,glycolysis/gluconeogenesis,pentose phosphate pathway,taurine metabolism,mineral absorption,and other metabolic pathways,which are closely related to differences in meat quality.4.The association analysis between proteomics and metabolomics showed that the key DEPs and DEMs affecting meat quality were different for different ages and different muscle parts of camel meat.A total of 285 DEPs and 87 DEMs were identified in three age groups.The commonly annotated pathways mainly have included nutrient related metabolic pathways such as carbon metabolism,amino acid biosynthesis,protein digestion and absorption metabolism,indicating that these DEPs and DEMs were directly related to nutrient changes between age groups.In addition,there was a significant correlation between 282 DEPs and 44 DEMs in the three muscle parts.These DEPs and DEMs were mainly enriched in metabolic pathways such as oxidative phosphorylation metabolism,amino acid metabolism,citrate cycle(TCA cycle),and glycolysis /gluconeogenesis,which were closely related to the formation of quality characteristics of meat.These studies highlighted that the association DEPs with DEMs were responsible for meat quality different.In summary,the analysis of camel meat quality indicators found that there were significant differences in tenderness and color among different age groups,which could be used as important evaluation indicators for establishing a camel meat grading system.Meat from younger camels could make consumers easy to accept and provide better quality characteristics.For meat from older camels,its color parameters and tenderness were poor,but its nutritional quality was better;it was recommended to use certain tenderization methods to improve its edible quality and facilitate processing and sales.The quality characteristics of camel meat from different ages,such as tenderness and color,were closely related to 311 differential proteins and 145 differential metabolites,of which 285 differential proteins and 87 metabolites have significant effects on the quality of camel meat from different ages.Bioinformatics analysis showed that these DEPs and DEMs were directly related to the metabolic pathways of nutrient changes in camel meat.In addition,the quality characteristics of camel meat from different muscle parts,such as tenderness and color,were closely related to 552 DEPs and 150 DEMs,of which 282 DEPs and 44 DEMs had significant effects on the quality of camel meat.The significant differences in the functions and metabolic pathways of these DEPSs and DEMs are the internal factors that cause the differences in quality traits.We can understand the internal regulation mechanism of the difference of quality characteristics in different ages and muscle parts of camel meat from the molecular level.