Biological Impedance Method For Detecting The Pork Freshness And Model Prediction

The current main methods to detect the freshness of meat are sensory testing;the physical and chemical testing,mainly including total volatile base nitrogen(TVB-N),pH,color and crude ammonia;microbial detection.However,these methods have the shortcomings,such as complicated pretreatment,complex and time-consuming operation,damage on the sample.For these reasons,it can not reach the purpose of rapid,accurate and nondestructive.This topic is based on biological impedance technique,with fresh pork longissimus dorsi as the research object,explore the biological impedance to be used for predicting the feasibility of the pork freshness.The main contents are as follows:1.Effects of storage time on the quality and bioimpedance of pork longissimus dorsiFresh pork longissimus dorsi were vacuum packaged and refrigerated in 4? for 10d and its quality index and bioimpedance were assessed.The results showed that with the increase of storage time,the total volatile base nitrogen increased(P<0.05),pH had no significant change(P>0.05),L values increased significantly(P<0.05),a*value had no significant change(P>0.05),b*values rose and the overall quality of pork gradually became poor.With the increase of excitation frequency,impedance magnitude presents the downward trend and impedance phase angle was first decline after an upward trend.With the increase of storage time,impedance magnitude under the same excitation frequency decreased significantly(P<0.05),while no significant change in impedance phase angle(P>0.05).The impedance magnitude of electric field direction perpendicular to the direction of the muscle fibers was higher than the electric field direction along the direction of the muscle fibers,and the impedance phase angle were almost the same.2.Prediction the freshness of chilled pork based on the bioimpedance and model buildingPrincipal component analysis and Pearson correlation analysis showed that total volatile base nitrogen had strong correlation with impedance magnitude.Using multiple linear regression models to select the specific frequencies,which had high correlation between total volatile base nitrogen and the impedance magnitude,Person correlation coefficient of horizontal direction all reached-0.69,Person correlation coefficient of vertical direction all reached-0.67.Prediction models of two electric field directions were established and the goodness of fit of model was high,the model of horizontal electric field was better than the vertical direction of the electric field.The accuracy of horizontal prediction model was up to 92%,the model was TVB-N?37.509-0.319×Hz 40 +0.401×Hz 50-0.224xHz 1.5k.Verification results showed that the prediction model could well predict the freshness of pork based on the measurement of the specific frequencies and other parts for pork also had a better prediction.