Effect Of Muscle Fiber Type Composition On Water-holding Capacity Of Pork

Water-holding capacity was one of the key indicators to evaluate meat quality,and it was associated with the color,texture and eating quality of fresh meat and also the economic benefits of the whole industry.The skeletal muscle was composed of multitudinous muscle fibers and muscle fibers can be classified into different types according to certain physiological and biochemical characteristics.The composition of muscle fiber type was correlated with water-holding capacity.This study aimed to: ?.analyze the correlation between muscle fiber type composition and pork quality.?.to clarify the effect of muscle fiber type composition on water-holding capacity of pork during storage at 4 °C.?.use the DIA proteomic strategy to compare the proteome differences at postmortem 45 min among longissimus thoracis(LT),semimembranosus(SM)and semitendinosus(ST)muscles.This study provided a reference for the classification of pork grade and pork quality control through manipulation of muscle fiber type composition.At first,a total of 90 crossbred(Duroc × Landrace × Yorkshire)pigs at age of 6 months were collected,and the LT,SM and ST muscles were excised from the left side of each carcass.The immunohistochemical staining method was used to detect the composition of muscle fiber types.Meat quality was measured and the correlation between the composition of muscle fiber type and meat quality among different muscles was analyzed.The results showed that LT and SM muscles contain predominantly type IIB fiber,respectively,60.4% and 50.1%.ST muscle was composed of more type I fiber.The correlation between muscle fiber type composition and water-holding capacity was also related to muscle type,but the percentage of type ?A muscle fibers in all three muscles was positively correlated with cooking loss while negatively correlated with moisture content,and the percentage of type ?X muscle fiber was negatively correlated with cooking loss.When analyzed the correlation in LT,ST,and across all muscles,the percentage of type ?B muscle fibers were positively correlated with cooking loss.Secondly,the effect of muscle fiber type composition on water-holding capacity during storage at 4 °C was investigated.The results showed that during storage at 4 °C,the purge loss,cooking loss,press loss and centrifuging loss of LT muscle were higher than that of SM and ST muscles.After a storage period of 1 d and 7 d at 4 °C,the drip loss was highest(P < 0.05)in LT muscle.And after 7 d stored at 4 °C,the contracted muscle fibers and muscle fiber-fiber detachments were observed more frequently in LT muscle compared with ST,while SM showed an intermediate frequency.The higher incidence of fractured muscle fibers was found in LT and SM muscles,while ST had the lowest degree of fractured fibers.The results of this study indicated that the muscle with higher content of type ?B muscle fibers had a lower water-holding capacity.And the contracted muscle fibers,muscle fiber-fiber detachments and fractured muscle fibers were more serious in muscles with more type ?B muscle fibers after a period of storage.In order to further understand the mechanism of the effect of muscle fiber type composition on water holding capacity,a DIA quantitative proteomics strategy was used to compare the differential abundance of proteomes in LT,SM and ST muscles at 45 min postmortem.A total of 3361 proteins were identified,and a total of 151 differential abundance proteins were selected under the condition of P < 0.05 and the fold change was 1.5.The results showed that structural proteins(B9ZSM8,A0A286ZY90,Q8HZW2),cytoskeletal proteins(F1RJ93,I3LPY1,A0A287AUH9,F1RJ93,Q6QAQ1,P10668,I3LPY1)and calcium ion binding proteins(A0A287AHD5,F1S2E2,K9J4R8)were down-regulated in LT.In addition,fructose-bisphosphate aldolase as one of the enzymes in those differential abundance proteins was up-regulated in LT and significantly enriched in glycolysis/gluconeogenesis pathway.The results indicated that the abundance of structural proteins,cytoskeletal proteins,and calcium-binding proteins were related to the water-holding capacity in muscles with different muscle fiber type composition.The differential abundance of enzymes involved in glycolysis pathway was also affect the water-holding capacity.