The Study On Reducing The Quality Loss Of Vacuum-cooled Chicken By Negative Pressure Liquid Injection And On The Impact Of Improved Chicken Quality

Cooling is one of the most important steps during the manufacture of chickenproducts. Compared with traditional cooling methods, vacuum cooling has theadvantages such as fast speed and high security. However, vacuum cooling may makethe meat lose water and affect its quality. In this paper, with the method of negativepressure liquid injection (NPLI) to add fresh liquid to the chicken, the quality loss ofvacuum-cooled chicken reduced and the edible quality of chicken was improved.Low-field nuclear magnetic resonance (LF-NMR) technology was used to determinethe moisture distribution of meat. Additionally, the best preservation liquid ratio andthe shelf life of corresponding processed chicken were studied during the vacuumcooling process.The main results were as follows:（1）The meat products were vacuum-cooled to different temperatures（50℃、40℃、30℃、20℃、10℃）, and then the quality loss rate, fluid infusion rate, shear forceand the color of the products were measured. The results showed that the maximumchicken quality loss rate was7.80%when the cooling temperature reached10℃. TheNPLI method had an impact on the fluid infusion rate and the shear force（p<0.05）,while this method had no obvious effect on the color of the chicken（p>0.05）. The fluidinfusion rate increased at first and then decreased. When the chicken was cooled to20°C in vacuum, the fluid infusion rate reached the maximum value of122.40%. Theshear force first declined and then increased, reaching a lowest point of2N/mm at20°C.（2）The moisture content and the moisture distribution of the negative pressureliquid injected chicken were measured when vacuum-cooled to different temperatures.It showed that the moisture content of chicken was first increased and then decreasedas the vacuum cooling temperature declines, and finally reached the maximum of72.90%at20°C. The result of LF-NMR analysis of the meat products manifested thatthe signal intensities of T22peak and T23peak were both increased, and the rangeability became larger when the temperature reduced. The T23peak moved backward, whichindicated that the content of immobilized water and free water in the chicken productsincreased through NPLI. The freedom degree of the free water also increased, whilethe bound water remained no change.（3）The volume of the injected fresh-keeping solution in chicken was measuredby different injecting time. The result was that the maximum volume was120ml withthe injection time of8s. This procedure is simply-operated and unpolluted. Throughresponse surface analysis, the optimal proportion of natural compound preservationsolution was with0.01%pimaricin,0.02%tea doxycycline, and0.01%Nisin. Bymeasuring the values of TVBN and TBARS, and the pH of the vacuum-cooled injectedchicken at4℃during storage, it can be seen that the various indicators of injectedchicken samples were better than the traditionally vacuum-cooled samples. Throughthe comprehensive evaluation of the indicators, the shelf life of the vacuum-coolednegative pressure liquid injected chicken and the non-injected chicken was about120dand80d, respectively.