Studies On Physical & Chemical Properties And Positive Regulation Of Meat In Qinchuan Cattle

With Qinchuan cattle as the subject, the present dissertation studies physical and chemical properties of carcass different part meats of Qichuan cattle; the properties indexes change of physical, chemical and histological of Qinchuan cattle beef in different month; connective tissue, adipose tissue, and muscle fiber diameter on tenderness of Qinchuan cattle beef; influence of different nutritional levels on Qinchuan beef quality;μ-Calpain localization in the muscle cell and influence on Qinchuan beef tenderness and microstructure; influence of lactic acid fermentation on Qinchuan beef quality; cloning, prokaryotic expression of Qinchuan cattle leptin receptor gene function (protein combinding) domain and the expressed protein combinding 1eptin property by the employment of physical, chemical, histological, immunohistochemical, RT-PCR, molecular cloning and expression methods, and so on, so as to provide theoretical basis and technical routes for production of high-grade and high nutritional value Qinchuan beef. The exprement results are presented in the follows:1. The objective of this research was to determine the difference in physical and chemical properties of Qinchuan cattle carcass different parts beef and to provide a theoretical basis for the production of high-grade and high nutritional value of Qinchuan cattle beef. Drip loss, shear force, cooked rate, intramuscular fat content and fatty acids composition, crude protein and essential amino acid(EAA) content, and microelements(Ca, Fe, and Zn) were determined by low temperature(4℃) hanging, texture analyzer, cooking, Soxhlet extraction, micro-Kjeldahl, GC-MS, amino acid analyzer, and ICP—AES methods respectively. The results were compared with each other. The results showed that the physical properties(drip loss, shear force, and cooked rate)and fat content of longissimus dorsi, serratus ventralis, rectus abdominis, and pectoralis profundus were more desirable than that of gluteus medius, trapezius, and semitendinousus(SD); The crude protein and EAA of gluteus medius, trapezius, and semitendinousus were higher than that of longissimus dorsi(LD), serratus ventralis, rectus abdominis, and pectoralis profundus; The structure of intramuscular fat acids, essential amino acids (EAA), and the microelements of different parts beef was silimar. The physical properties and fat content of pectoralis profundus, serratus ventralis, longissimus dorsi, rectus abdominis are more desirable; consequently, their commercial value are higher. The crude protein and EAA content of trapezius, semitendinosus, gluteus medius are higher, and the intramuscular fat is lower, so, they have higher nutritional value. Crude fat content is negatively correlated with the beef nutritional value; while crude protein is the opposite; and the nutritional value of polyunsaturated fatty acids (PUFA) of intramuscular fatty acid is desirable. The marbling abundance and PUFA content of Qinchuan beef should be further promoted.2. Physical, chemical and histological properties of Qinchuan cattle beef in different month were explored in order to provide a theoretical basis for the production of high-grade Qinchuan beef. Shear force, pressurized water loss rate, cooked loss, water content, intramuscular fat content and fatty acids composition, crude protein and amino acids(AA) content, meat colour value(L﹡﹡ a﹡﹡ b﹡) were determined. The muscle intramuscular connective tissue in paraffin-dyed sections were measured by muscle fiber gap. The muscle fiber diameter was measured by scanning electron microscope. The results showed that the different month beef shear force increased significantly(p<0.05), pressurized water loss rate, cooking loss, and water content were reduced significantly(p<0.05), the content of intramuscular fat and crude protein increased significantly(p<0.05), the of content saturated fatty acid(SFA) and essential amino acid(EAA) increased, unsaturated fatty acids(USFA) content reduced, L﹡ value reduced significantly(p<0.05), a﹡ value increased significantly(p<0.05), the muscle fiber gap and the muscle intramuscular connective tissue increased, the muscle fiber diameter increased significantly(p<0.05). With the age increasement of Qinchuan cattle, the content of intramuscular fat and crude protein increased significantly(p<0.05), pressurized water loss rate, cooked loss, water content were reduced significantly(p<0.05), and the beef commerical value increase; EAA content increase, and protein nutritional value increase; USFA content reduced, and their nutritional value reduce; With the age increasement of Qinchuan cattle, the muscle fiber diameter is the primary factor for beef tenderness.3. Studies on connective tissue, adipose tissue, and muscle fiber diameter on tenderness of Qinchuan cattle beef, and analysis the main factors on beef tenderness of Qinchuan cattle, in order to provide a basic theory for beef production and quality improvement. Influence of connective tissue, adipose tissue, and muscle fiber diameter on beef tenderness was analysed by physical and chemical analysis, muscle histology, RT-PCR, and so on. The results showed that the tenderness and intramuscular fat of longissimus dorsi were higher than that of semitendinosus(p<0.05). The connective tissue of longissimus dorsi are main fatty tissue, with loose structure. The connective tissue of semitendinosus is main collagen protein (collagen fibers), with compact structure and hardness. The collagen protein of semitendinosus is higher than that of longissimus dorsi, while the content of fat was the opposite. The collagenⅠc ontent was not significant difference between longissimus dorsi and semitendinosus(p>0.05). Muscle fiber diameter longissimus dorsi is bigger than that of semitendinosus. Muscle fiber membrane impact the sensory tenderness of beef. The kind and content of intramuscular connective tissue in different parts of Qinchuan cattle carcass are different. In general, the ratio between collagen protein and intramuscular fat to the tenderness has greater contribution than that of muscle fiber diameter, and it is a key fator for beef tenderness.4. Influence of different nutritional levels on Qinchuan beef quality in order to provide a basic theory for the production of high-grade beef. The calf were divided, and were fed in three different nutritional levels, i.e. low, middle and high. Muslim Slaughter was used, and longissimus dorsi was choosed. Different nutritional levels on beef quality were analysed by physical and chemical analysis, and muscle histology. The results showed with the enhancement of the energy level, the tenderness, the intramuscular fat content, and the marbling(intermuscular fat) abundance of high energy level group beef was significantly higher than other groups(p<0.05); the marbling abundance and the intramuscular fat content were positively correlated with the beef tenderness, it is the same as that of water holding capacity(WHC), and water loss rate; pH significantly decreased(p<0.05); sarcolemma significantly thickened; there were no significant change on fat content and fatty acid composition, protein content and amino acid(AA) composition, and microelements(p>0.05), and other chemical and histological properties. With the enhancement of nutritional levels, the beef can be significantly improved in tenderness (p<0.05), marbling abundance, and commercial value. But the beef nutritional value will be further improved.5. Study onμ-Calpain localization in muscle cell, and its tenderization effect on beef were explored by activation ofμ-calpain to provide a theoretical basis for beef tenderizing in postmortem.μ-Calpain position in muscle cell was located by paraffin-dyed sections of immunohistochemistry; Qinchuan beef was injected different concentration calcium chloride solution(μM and mM), meat samples were vacuum-packed at 4℃for 72 h, shear force was measured by texture analyzer, muscle fiber microstructure change was observed by paraffin-dyed sections, myofibril fragmentation(MF) and myofibril was observed by atomic force microscope, activation and degradation ofμ-Calpain were analysed via western blot, change of muscle fiber membrane was observed by environmental scanning electron microscope. The results showed thatμ-Calpain mainly exists in the cell membrane and the cytoplasma; tenderness of meat samples was no significant improvement(p>0.05); little change was in microstructure of muscle fiber;there was some amount myofibril fragmentation; myofibril membrane ruptured,and muscle wire is clearly visible; Exogenousμmol / L concentration CaCl2 can activateμ-Calpain zymogen;μ-Calpain has little degradation effect on the muscle fiber membrane structure.μ-Calpain mainly exists in the cell membrane and the cytoplasma;μ-calpain have a certain degradation activation on beef myofibrils, but its hydrolytic activity is far lower than that of m-calpain.6. Qin chuan beef qulity change was studied in lactic acid fermentation. Dip Qin chuan beef into different concentration of NaCl(10 g.L-1, 20 g.L-1, 30 g.L-1, 40 g.L-1, 50 g.L-1) and mensurate beef acidity and TVB-N. Add lactobacillus (1 g.L-1, 2 g.L-1, 3 g.L-1) and ferment respectively(1 h, 2 h, 3 h, 4 h) and mensurate beef acidity and TVB-N and shear force. The results showed lactic acid fermentation can improve Qin chuan beef quality and protect beef from rancidity very significant(p﹤0.01) and the optimum fermentation conditions were 30 g.L-1NaCl and 2～3 g.L-1 Lactobacillus and 2～3 h fermentation. The beef quality index of lactic acid fermentation were as following, TVB-N≤5.0mg.100g-1, shear force≤4.00 kg, acidity≥1.0 g.kg-1. Beef flavor ingredients are more rich. Lactic acid fermentation can be very significant (p <0.01) on improvement of beef quality, and very significant (p <0.01) on inhibition of beef corruption. Lactic acid fermentation may improve the eating and processing quality of beef.7. Cloning and expression of Qinchuan catlle leptin receptor gene function (protein combinding) domain, and analysis of the expressed protein combinding leptin properties, in order to provide theoretical basis for regulation leptin receptor on leptin combinding. The cDNA of leptin receptor gene was amplified from muscle mRNA of Qinchuan cattle by PCR. PCR product was cloned into the T vector pMD18-T to construct plasmid for sequencing. Then the cDNA was subcloned into the prokaryotic expressing plasmid vector pET30a (Nde1/Xho1) and transformed into host Escherichia coli strain BL2l(DE3) for expression. The expression of leptin receptor function protein was induced by IPTG, and was identified by SDS-PAGE. The protein was purified by Ni-NTA column. Combinding leptin function of the expressed recombinant protein via high performance liquid chromatography-frontal analysis(HPLC-FA). The results showed that leptin receptor function gene was highly expressed in Escherichia coli;and the expression product was observed with soluble protein and inclusion body; Western blot showed that the recombinant protein was recognized by his antibody specifically; The expressed recombinant protein has combinding leptin function. In vitro expressed exogenous Lepr gene function protein has combinding leptin function, and the study laid the foundation for inhibitting Qinchuan cattle energy metabolism, and fat deposition through regulation of leptin receptor on combinding leptin.