The Research Of Effects Concernning Calpain And Calcium During Postmortem Conditioning Of Pork

Of all the attributes of the quality of meat,tenderness is considered as the most important one by consumers,for pork.Postmortem conditioning is the basic way to improving tenderness.To update,there is not yet the conclusion about the conditioning mechanism.This paper would research on effects of calpain and calcium during postmortem conditioning of pork,further proved the conditioning mechanism of pork,to provide more evidence to support controlling postmortem conditioning process.The establish -ment of pork tenderness characteristics index system,would provide evidence for establishing tenderness forecasting model of pork.Experiment 1:establish the characteristics of pork tenderness index systemLD,PM and SM of DLY three-way cross combination were dissected,and the tenderness indexs of each cut aged at hour 0,24,48,72,96,120,144 and 168 was studied respectively,the tenderness indexs including CAF,MFI,SFV and related the results of SDS-PAGE whole muscle protein, to comprehendsive evaluation of pork's tenderness during postmortem conditioning in the process of change.The results showed as follows:(1) Condition time influenced tenderness of pork significantly at P<0.01,with conditioning time extending,tenderness levels significantly increased (P<0.01).The initial tenderness of pork between different cuts significantly different (P<0.05),the initial tenderness of PM was best,SM was second and LD was thrid.Conditioning speed of different was not the same,PM had the fast conditioning speed at the early time of conditioning. After conditioning.the tenderness of three different cuts at 168h was different significantly (P<0.01).PM was sill had the best tenderness, tender than both SM and LD.(2) The activity of CAF dropped significantly at early postmortem conditioning time (P<0.01),and the tenderness was improved significantly (P<0.05).After conditio -ning 72h,the speed of CAF activity declining was gradually slow down,and the speed of tenderness increasing was slow down too,proved that calpain played a major role during the postmortem conditioning of pork,and its mainly effect on the early time of postmortem conditioning.(3) there was a very significant negative correlation between MFI and SFV (P<0.01),there was a significant positive correlation between SFV and CAF(P<0.05), proved that MFI and CAF activity could be as the tenderness indicators of pork.(4)During postmortem conditioning,along with the improvement of muscle tenderness,the SDS-PAGE photogragh of whole-muscle proteins had emerged in the fragments with the size of about 30kDa.This fragments were degradation products from Troponin-T.Color of this bands gradually deepened,proved that the fragment with the size of about 30kDa, also could be as one of the indicators of pork.Experiment 2: Different injection processing effects on the conditioning of porkLD cut from DLY three-way cross combination carcasses, samples were injected (10% of weight) with distilled water(control), 0.2mg/ml Leupeptin, 200mmol/L Znic chloride, 200mmol/L Calcium chloride, 0.2U CAF, 0.2U CAF+200mmol/L Calcium chloride, each cut aged at day 0,1,3,5,7 was studied respectively, the tenderness indexs including activity of CAF, MFI, SFV, and related the results of SDS-PAGE whole muscle protein, The results showed as follows:Exogenous calpains inhibitors,Leuptptin and Znic chloride,slowed the speed of pork conditioning significantly,in the course of postmortem conditioning the level of tenderness was almost unchanged (P>0.05).Calcium chloride injection and CAF injection, The level of tenderness to the control group was significantly improved (P<0.01), and greatly shortened pork aging period.Along with the extension of aging time, CAF activity was significantly lowed down(P<0.01), and the speed of tenderne -ss improving slowed down gradually.Increasing the concentration of Ca²⁺ in muscle or increasing the content of calpain,would both contributed to enhancing the tenderne -ss of pork.Further explaned that calpains played an important role in myofibril degra -dation,and it needed a certain concentration of Ca²⁺ to be activated,and its mainly affected at the early period of conditioning time.Experiment 3: Effects of calcium solution injection on pork conditioningThis experiment included two parts.The first part was that LD cut from DLY three-way cross combination carcasses,samples were injected(10% of weight) with distilled water(control), 1mmol/L, 10mmol/L, 100mmol/L, 200mmol/L, 300mmol/L Calcium chloride.And the second parts was that LD samples were injected(10% of weight) with distilled water(control),100mmol/L Calcium lactate,100mmol/L Calcium gluconate,100mmol/L Calcium chloride.Both each cut aged at day 0,1,3.5,7 was studied respectively,the tenderness indexs including activity of CAF, MFI, SFV, and related the results of SDS-PAGE whole muscle protein,discussed the role which was Ca²⁺ palyed in the conditioning of pork,and the possibility of organic calcium used in the pork tendering.The results showed as follows:(1)The concentration of Ca²⁺ injected in LD was more than 100mmol/L,coule be improving the tenderness of pork significantly,and to a certain concentration,the tenderness improved greatly,with the concentration of Ca²⁺ increasing.But when the concentration of Ca²⁺ was biger than 200mmol/L,the increasing space of tenderness was limited.This proved the concentration of Ca²⁺reached on lOOmmol/L could be improved the tenderness of pork,but in order to got better tenderaess,the concentration of Ca²⁺ could increased to 200mmol/L.(2)This experiment also try to choose a suitable source of organic calcium to replace the calcium chloride,the results of experiments showed that calcium gluconate on the role of tendering pork was not obvious, 100mmol/L of calcium lactate could be played with 100mmol/L calcium chloride the same role.Therefore,the organic calcium to replace the calcium chloride is feasible.