Effects Of Combined Heat And Ultra-high Pressure Treatment On Quality Of Black Pork

The high-pressure technology is a new technology developed in the last decade，itcan improve meat tenderness and extend shelf life under the premise of the meat flavorand nutrients are not affected. Pre-rigor meat pressure treatment individually can play agood tender role, but the effect of post-rigor meat pressure treatment is not verysatisfactory. Meanwhile, the inhibitory effect of pressure treatment on spore is not verygood. Therefore, in recent years, high pressure is applied with heat treatmentcombination. In this thesis, the effects of high pressure(0.1to600MPa) applied atdifferent temperatures (20to60℃) for20minutes on texture，myofibrillar protein, lipidoxidation and color of black pork post-rigor longissimus dorsi and its sausage werestudied.(1) Effects of combined heat and ultra-high pressure treatment on muscle tissue issignificant. Texture profile analysis shown that the hardness, springiness and chewinessof sample increase with increasing temperature at ambient pressure, and increasedsignificantly at60℃. Meanwhile, when pressure was applied at room temperature, thehardness, springiness and chewiness of sample increased again with increasing pressure,the texture of muscle tissue changed significantly at400MPa. When the pressureincreased to400MPa above, the hardness, springiness and chewiness decreased.Similar results were found at40℃, but the hardness decreased at60℃when thepressure increased to400MPa and above. Effects of combined heat and ultra-highpressure treatment on sausage were similar to muscle.(2) The pH of muscle tissue is also affected by ultra-high pressure and temperature,the structure of muscle proteins were changed by combined heat and ultra-high pressuretreatment, so that the acidic groups reduced, pH increased with increasing pressure.(3) When the myofibrillar proteins were treated after ultra-high pressure, the bandof actin was clearly visible in SDS-PAGE profiles from supernatant at0.1MPa, butactin band become blurred when the pressure increased to200MPa, and disappeared at400MPa. With the pressure increased, it appeared again. The solubility of troponin Tand troponin I/C in SDS-PAGE profiles from supernatant increased with increasingpressure, the most significant pressure is400MPa. In the presence of SDS and2-mercaptoethanol, tropomyosin is divided into two bands, similar results to thosefound in troponin T and troponin I/C were found. The concentration of three myosin light chains were both low in the supernatant and the precipitate, but when the pressureincreased to400MPa and above, the three bands were visible in the supernatant, thatshown that the concentration of three myosin light chains increased with increasingpressure. But in SDS-PAGE profiles from precipitate, the changes of protein bandswere opposite.(4) When the black pork were treated at different pressure and temperatures for30minutes, lipid oxidation rate was significantly accelerated. TBA test shown that TBAvalues have a significant increase as pressure increase. When the samples were storagedat4℃for7days, TBA values were significantly higher than the first day of TBAvalues.The change of TBA values of sauage is similar to meat, TBA values increasedwith increasing pressure. VE is an effective free radical terminating agent, It can makelipid oxidation reaction chain terminated. The results shown that, VE has goodantioxidant effect.(5) Effects of combined heat and ultra-high pressure treatment on the color ofsausage were complicated. The appearance of the sausage has significant changes, thecolor of sausage gradually changes from red to pink, then to gray after pressuretreatment at20℃and40℃. When treated at600MPa, the sausages became brown. L*values increased with increasing pressure, on the contrary, a*values decreasedaccompanied by a rise in pressure. Whiting phenomenon of sausage (L*valuesincreased) probably due to the denature of globin under ultra-high pressure. When thesausage was treated by200MPa at60℃, L*and a*values did not appear a significantchange. Because that had caused denature of myoglobin and myofibrillar proteins underambient pressure at60℃. But whenpressure increased to400MPa, L*and a*valueschanged significantly.(6) The results shown that the effects of nitrite and monascorubrin on L*valueswere significant (P＜0.05）. But it did not change significantly at60℃（P=0.375）. Theeffects was also significant on a*values. Nitrite and monascorubrin play a role in theimprovement of the color of sausages.