Effects Of Different Muscle Fiber Type On Beef Quality And Caspase-3

Beef quality is considered to be the most important criterion for meat quality by most consumers.Aging can improve the overall quality of beef,especially beef tenderness.Muscle fiber is the basic structural unit of muscle.Muscle fiber type can affect beef quality.The relationship between muscle fiber types and postmortem beef quality is still under discussion.Supraspinatus(SU),infraspinatus(IF),triceps brachii(TB),psoas major(PM),longissimus dorsi(LD),semitendinosus(ST),semimembranosus(SM)and biceps femoris(BF),which are composed by different ratio of muscle fiber types,were used to study the relationship between beef quality and muscle fiber type.ATPase staining,SDS-PAGE and transmission electron microscopy technology was used to study muscle fiber characteristics,quality difference,myofibril protein degradation,myofibril ultrastructure and caspase-3 activity of eight major muscles.The aim was to study the effects of muscle fiber types on beef quality.This study can provide data support for fine aging of different muscles.The results as follows:(1)The muscle fiber types and quality of different parts of beef were studied.The muscle fiber characteristics and quality characteristics of 1h were determined.The results showed that PM,LD and BF had the highest muscle fiber ratio of type ?,type ?A and type ?B fibers,respectively.The diameter order was type ?B>?A>?.The diameters of the type ?,type ?A and type ?B fiber of PM were smaller than other parts.PM had lower Warner-Bratzler shear force(WBSF),hardness,gumminess,pH and b*value,and had higher cohesiveness and pressing loss;ST had lower pressing loss,cohesiveness and resilience,and had higher L* value.LD had lower chewiness,resilience and springiness.BF had higher springiness,cohesiveness and chewiness.Muscle fiber area and diameter of type ?,?A and ?B fibers were positive correlated to WBSF,hardness and cooking loss.Muscle fiber area and diameter of type ?,?A and ?B fibers were negative correlated to pressing loss.The muscle fiber ratio of type ? was negative correlated to hardness and WBSF(p<0.05).The muscle fiber ratio of type ?B was positive correlated to WBSF(p<0.05).Therefore,increasing the proportion of type I fiber,reducing the proportion of type ?B fiber is beneficial to improve the beef tenderness.(2)The change regularity of beef quality was studied.The quality changes of SU,IF,TB,PM,LD,ST,SM and BF during postmortem period were determined.With the aging time increasing,pH of eight major muscles were first decreasing and then increasing.PM had higher pH decline rate than other parts.The muscle fiber ratio of type ? was negative correlated to pH rate of change(r=-0.77).The muscle fiber ratio of type ?B was positive correlated to pH rate of change(r=0.78).With the aging time increasing,WBSF of eight major muscles were first increasing and then decreasing.PM had higher pH decline rate than other parts.PM had lower WBSF than other parts(p<0.05).The muscle fiber ratio of type ? was negative correlated to WBSF rate of change(r=-0.56).The muscle fiber ratio of type ?B was positive correlated to WBSF rate of change(r=0.50).BF had the highest WBSF rate of change,and PM had the lowest WBSF rate of change.ST had the highest L* value and PM had the highest a* value.With the increasing of aging time,a* value increased.(3)The change of protein degradation and caspase-3 activity in different beef during the maturation were studied.The MFI,protein solubility,myofibrillar degradation and caspase-3 activity of PM,LD and BF were determined.Results showed that with the increasing of aging time,the MFI of PM was higher than LD and BF.The myofibrillar degradation rate of the BF and LD was faster than PM.The troponin-T and desmin degradation rate of BF and LD was faster than PM.With the increasing of aging time,the caspse-3 activity of three major muscles were first increasing and then decreasing.The caspse-3 activity of PM and LD was negatively correlated with WBSF,pressing loss and hardness.The caspse-3 activity of BF was significantly positively correlated with MFI(p<0.05),and negatively correlated with pressing loss.The initial MFI and caspase-3 activity was positive correlated to muscle fiber ratio of type ?(p<0.05),and negative correlated to muscle fiber ratio of type ?B(p<0.05).The MFI rate of change was negative correlated to muscle fiber ratio of type I(p<0.01),and negative correlated to muscle fiber ratio of type ?A(p<0.05),and positive correlated to muscle fiber ratio of type ?B(p<0.01).