Study On The Effects And Mechanism Of Ultra Sonic Treatment On Beef Quality

At present,the researches about the ultrasound mainly focus on the effects of ultrasound on beef quality,while few studies investigated it effects on the protein degradation and oxidation.Therefore,the objective of this study was to investigate the effects and mechanism of different ultrasound treatments on beef quality through measuring calpain activation,protein degradation myofibril fragmentation index and protein denaturation.The specific research contents and results are as follows:1.Effects of ultrasound treatment on beef quality during agingTwelve left semitendinosus muscles of Luxi cattle with same gender and similar weight were randomly divided into control group,ultrasound treatment for 20 min,and 40 min group.Each treatment was set up with 4 animal repeats and samples after treatment were aging for 0,2,and 6 d at 4℃,respectively.The pH values,meat color,Warner-Bratzler shear force and water holding capacity(purge loss,cooking loss,pressing loss and measurement of Low-Field Nuclear Magnetic Resonance)were determined.The results showed that the ultrasound treatment significantly increased the pH value of beef at 0 d after treatment,and decreased the purge loss and cooking loss(P<0.05)without significant effect on the pressing loss.The ultrasound treatment significantly improved the L*value of beef samples,decreased the a*value,and reduced the WBSF at 2 and 6 d(P<0.05).The results of LF-NMR data showed that the ultrasound treatment group had more immobilized water and less free water(P<0.05).2.Effects of ultrasound treatment on the microstructure and protein degradation of beef during agingSarcomere changes can directly reflect the influence of ultrasound on myofibrillar structure.The major components of the cytoskeleton proteins,including desmin and troponin,have the function of maintaining the order and integrity of the muscle cell structure and controlling the contraction of muscle cells.Calpain may affect the quality of beef through the regulation of myofibrillar protein degradation.This chapter investigated the effects of ultrasound treatment on beef myofibrillar structure,autolysis of calpain and protein degradation during aging to determine the influence of ultrasound on the quality of beef and its mechanism.Results showed that the swelling at the A-band region was observed in the muscle fibers of the two ultrasound-treated samples at 2 and 6 d in particular near the H-band.The region near the Z-line became irregular and muscle fibers were separated by gaps,while the control group of the sarcomere structure was relatively complete.The myofibrillar fragmentation index was also significantly improved by ultrasound indicating that ultrasound treatment promoted the ripening process of beef.The autolysis of μ-calpain in ultrasound samples of 0 d was increased,while the degradation rate of desmin and troponin-T was significantly higher than the control group at 2 and 6 d(P<0.05).The above results showed that the ultrasound treatment can promote the autolysis of μ-calpain and accelerate the degradation of myofibrillar protein.3.Effects of ultrasound treatment on the protein and lipid oxidation of beef during agingThe effects of ultrasound treatment on the protein carbonyl content,the content of free protein thiol group,protein solubility and lipid oxidation were studied in this chapter.Results showed that at 2 and 6 d after ultrasound treatment,the protein carbonyl content of ultrasound group were significantly increased,free protein thiol group content was decreased,total protein solubility and myofibrillar protein solubility were lower.Beef TBARS determination showed ultrasound treatment significantly increased the degree of lipid oxidation.The above results indicated that ultrasound treatment promoted the degree of lipid oxidation and protein oxidation.