Study On Dection Method Of Pork Freshness Based On Impedance Spectroscopy

Freshness is an important indicator of the quality of fresh pork and is also an essential element in determining whether consumers accept pork products.However,the huge fresh pork market has always lacked a quick,easy,non-destructive and accurate method of measuring freshness.Impedance spectroscopy is a special electrochemical testing technique.In recent years,studies have shown that it can produce different responses to changes in biological tissues.In particular,the medical field began to study the evaluation of the health of biological tissues and organs by impedance spectroscopy.Impedance spectroscopy studies on biological tissues have shown that impedance spectroscopy can also be applied to the freshness evaluation of fresh pork.This paper takes the evaluation of freshness of fresh pork as the target,and uses the sensory evaluation as the standard,and the total number of volatile base nitrogen and colonies as evidence.Based on the impedance spectroscopy technique measurement,the impedance spectroscopy equivalent circuit model is used to evaluate the fresh pork.A evaluation method of freshness characteristics of fresh pork was established by changing the impedance characteristics of the decay process.The research content of this paper mainly includes:(1)A standard method for sensory evaluation of freshness of pork was designed,including environmental design,personnel screening and evaluation of product evaluation results.Fresh pork was classified into fresh meat,secondary meat and spoiled meat under different quality conditions.Four sensory attributes of color,odor,elasticity and viscosity were determined.Attribute weights were introduced to study the importance of each sensory attribute index.The odor attribute weight was the highest(0.29),indicating that it had the greatest influence on the sensory staff's evaluation of pork freshness.The other three attributes have similarity of influence.Two biochemical indicators(the total number of colonies and volatile base nitrogen)of fresh pork in the process of corruption were selected for testing,which corroborated the sensory evaluation for judging the accuracy of pork freshness.The results showed that fresh pork was stored in a constant temperature and humidity chamber at 35 degrees Celsius and 70% humidity.It was stored for 1 to 4 hours as fresh meat.After storage for 5-7 hours,it became secondary meat.After storage for more than 8 hours,it became Corrupted meat provides a reference model for fresh pork freshness ratings.(2)An impedance measuring device was designed,including a fourpin sensor and a sample cell suitable for measuring the impedance characteristics of pork.With the fitting error and impedance amplitude as the index,the measurement parameters and measurement methods in the impedance measurement process are optimized.The results show that the impedance amplitude decreases with the increase of pork storage time.The impedance result is optimally fitted and the error is the smallest at 1.08 Hz.The magnitude of the impedance measured when the excitation current is perpendicular to the pork fiber is greater than the amplitude of the impedance measured when the excitation current is parallel to the pork fiber,and the error is smaller,which is more suitable for comparing the impedance test of pork.(3)Try to introduce the equivalent circuit model in the field of electricity,and evaluate the change of freshness of pork by comparing the changes of various parameters in the equivalent circuit model.Two equivalent circuit models are designed.One is that the capacitor element and the resistance element are connected in parallel and the series resistor is used to form an equivalent circuit model.The other is a constant phase component and a resistor element in parallel with a series resistor.An equivalent circuit model composed of three equivalent circuit components.In both models,both the capacitance C and the tantalum capacitance CPET increase as the degree of deterioration of the pork deepens.At the same time,before the storage time of 5 hours,the capacitance C value is less than 6MF,and the error is small.After 8 hours of storage,the capacitance C value is greater than 6.5MF.The tantalum capacitor CPE-T value is greater than 240 kF after 5 hours of storage and greater than 270 kF after 8 hours.Therefore,both the capacitance C and the tantalum capacitance CPE-T reflect the change in electrical characteristics of the pork as it is stored,and can be used to evaluate the freshness of the pork.