| Water holding capacity(WHC)is one of the key indicators to measure pork quality,which will directly affect the color,texture,taste and flavor of meat quality.WHC is closely related to the economic benefits of the industry.The diameter and number of muscle fibers are the key factors affecting the water retention and tenderness of meat and the content of intramuscular connective tissue(IMCT)is closely related to the volume shrinkage of meat.Based on different contents and characteristics of muscle fiber and connective tissue in different muscle types,the purpose of this study is to investigate the influence of thermal protein denaturation on water holding capacity of boiled pork,as well as combine low-temperature long-time cooking with conventional cooking to improve meat quality.The quality of pork from different parts are different.(1)Effect of thermal shrinkage of muscle fibers and perimysium on water holding capacityFive commercial crossbred pigs(Duroc×Landrace×Yorkshire crossbred,6 months age,110±10kg weight)were obtained from the local supermarket.The longissimus thoracis(LT),semimembranus(SM)and semitendinosus(ST)were taken as the experimental materials.After being cut into pieces,they were heated in a boiling water bath for 45 min.The WHC,structural changes and protein denaturation were analyzed to clarify the influence of conventional cooking on the WHC of different muscle types.The WHC of ST was better than that of LT and SM(P<0.05),and the volume shrinkage was smaller.During the heating process,the myofibrillar protein thermal denaturation,surface hydrophobicity increased(P<0.05),sarcomere contraction,which squeeze water out.The surface hydrophobicity and decorin content of ST were lower(P<0.05),and the sarcomere length,collagen content and thermal solubility of ST were higher.IMCT contributed to maintain the integrity of muscle fiber structure,and the gelatinized collagen structure contributed to improve the WHC.(2)Study of the influence of two-stage heating conditions on pork based on orthogonal experimentThe results showed that there were significant differences(P<0.05)in cooking loss,centrifuge loss,shear force and color of meat samples under different heating conditions,and the coefficient of variation ranged from 8.47%to 20.98%.By factor analysis,three main factors were extracted based on eigenvalues greater than 0.6,and the cumulative variance contribution rate was 80.81%.Meanwhile,the quality evaluation model was established as F=0.025×M cooking loss+0.016×M centrifugal loss-0.189×M shear force-0.389×M L*value+0.490×M a*value+0.448×M b*value.According to the score,verification,the results of four factors and three levels of orthogonal test showed that the first stage(low temperature):heating temperature 48°C,heating time 2 h;the second stage(high temperature)heating temperature 90°C,heating time 15 min.According to the score results of different factors,low temperature heating temperature and time have greater influence on meat quality.In the process of segmenting heating,higher heating temperature will affect the structure change of muscle fiber,and then affect the water holding capacity and water distribution of meat.Compared with low-temperature heating,the water retention and other qualities of segmenting heating meat are more similar to those of high-temperature heating,which may be related to the denaturation of collagen in intramuscular connective tissue under high temperature conditions.Compared with simple low-temperature and long-time cooking and conventional steaming,segmenting heating can better maintain the quality and safety of meat.Compared with low temperature long time cooking,the quality of water retention of meat in two-stage heating is more similar to that of stewing,which may be related to the degeneration of collagen in intramuscular connective tissue under high-temperature conditions.Two-stage heating can maintain the quality and safety of meat.(3)Effect of two-stage heating on muscle fibers and IMCT in porcine musclesIn order to further explore the influence of different heating methods on WHC,nine commercial crossbred pigs were chosen as experimental materials,split after slices in two-stage heating condition.The WHC,structural change and protein denaturation were analyzed to clarify the influence of heating condition on the WHC of different muscle types.The results showed that the WHC of ST was better than that of LT and SM.During the two-stage heating,the denaturation of myosin was much more severe and the lateral contraction of meat increased.The content of connective tissue in ST muscle is higher but the thermal stability is worse.The triple helix structure of collagen molecules unwinds during heating.The content of cross-linking of hydroxylysine pyridine and lysine pyridine is less,which makes the collagen fiber network shrinkage less. |
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