| The loss of juice after slaughter of meat products has had an adverse effect on production and consumption.In this experiment,conventional chilling(CC)and rapid chilling(RC)treatments were applied to the longissimus dorsi muscle,and the acidity value,juice quality loss,and energy metabolism in the muscle during the aging of the two groups were determined.Changes of the key products and their rate-limiting enzyme activities,muscle cell microstructure,and myofibrillar protein(MP)characteristics,etc.,explored the water-holding capacity and MP functional properties of beef during postmortem aging by different chilling methods.In order to compare theoretically whether the chilling method can reduce the loss of juice in the muscles,provide basic data for further research on the changes in the waterholding capacity mechanism of beef under rapid chilling.The findings are as follows:1.The pH and apparent water holding capacity of the longissimus dorsi muscle under different chilling methods during postmortem aging were studied.Under rapid chilling,the pH decreased slowly within 24 h after slaughter,and the pH(pHu)of 5.58 was greater,there was a significant difference in chilling methods between 6h,12 h,and 168 h after slaughter(P<0.01).The juice loss increased after slaughter and decreased or remained unchanged after 72 hours.Within 48 hours after rapid chilling,the rate of weight change was small and the juice loss rate was large.In the rapid chilling group,the pressure loss was 25.78%,the cooking loss was 41.86%,and the drip loss was 4.54% after 168 hours post-mortem.2.The energy metabolism of the longissimus dorsi muscle under two chilling modes during postmortem aging was studied.The levels of muscle glycogen,adenosine triphosphate(ATP),lactate dehydrogenase(LDH),creatine kinase(CK)decreased,and glucose(Glucose,Glc),Lactic acid(HL)and Glycolysis potential(GP)rose first and then decreased.After rapid chilling,the metabolic rate is low and the enzyme activity are low in the early postmortem period.There was a significant difference between the aging points of ATP content(P<0.01).In the RC group,the ATP content was 219.21 ?mol/gprot,the LDH content was 9.01 U/gprot and the CK content was 3.46 U/mgprot at 72 h postmortem.3.The microstructural changes in beef aging under two chilling modes were studied.The muscle fiber area is still decreased and the muscle fiber clearance increases after postmortem aging.The muscle fibers of the CC group were significantly dispersed at 72 h after slaughter,and the cell gap was larger.The muscle fibers of the RC group were closely arranged and did not change significantly from 0h to 12 h.The cross-sectional area of muscle cells in the RC group was lower than that in the CC group.4.Changes in the protein properties of the longissimus dorsi muscle under different chilling methods during postmortem aging were studied.Combined with albumin(Combine BPB)content of the conventional chilling group reached a peak of 24.45?g at 72 h after slaughter,rapid chilling group reached a maximum of 21.82?g at 48h;sarcoplasmic protein solubility reached a maximum of 76.77mg/g,81.66mg/g at 72 h.;the gel water-holding capacity of the two groups increased to 89.83% and 90.73% respectively at 168 h after slaughter.Emulsifying activity index(EAI)and emulsion stability(Emulsifying stability,ES)decreased first and then increased.Rapid chilling in the early postmortem period changed slowly.After chilling MP oxidation is low.Degradation products of Desmin in the RC group appeared earlier in the vicinity of the maximum period of the stiffness.In summary,rapid chilling can effectively improve the water-holding capacity of the longissimus dorsi muscle,and the maximum period of rigor mortis is completed as soon as possible.After inhibit the early slaughter protein degeneration,rapid chilling has a protective effect on the integrity of the protein structure. |
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