Non-destructive examination for freshness of eggs based on dielectric properties and yolk index regression model

Abstract: Egg is an important source of protein nutrition in China. Eggs which have high protein, low fat and a variety of nutritional elements, easy to digest and absorb, and so on are popular with people. Detection of freshness of egg effectively is not only to protect the interests of consumers, but also beneficial to the management of producers and operators. At present, fluorescence spectrum, infrared spectrum, image processing and dielectric property detection are the main methods of egg nondestructive testing. Dielectric property detection technology is a fast and nondestructive testing technology. The characteristics of dielectric properties have been shown to have special advantages in the field of agricultural product quality evaluation and grading. There are many achievements in non-destructive testing of agricultural products by using dielectric properties. In order to achieve a more accurate and rapid determination of egg yolk index, we studied the relationship between the dielectric properties and egg yolk index. Based on the dielectric properties, we established an egg fresh degree nondestructive detection model, and obtained the egg yolk index information. In this experiment, we used parallel plate method to measure the dielectric properties of different fresh eggs between 1 and 200 kHz. This experiment was based on different fresh degree eggs. We measured the dielectric properties of different fresh eggs between 1 and 200 kHz by using the parallel plate method. We used MATLAB to analyze the effects of frequency and freshness on the dielectric properties of eggs, and to draw the curve. The research results showed that the measurement frequency and the fresh degree had a significant effect on the dielectric properties. Between 1 and 200 kHz, the relative dielectric constant and dielectric loss factor of eggs decreased with the increase of the test frequency. When the frequency was less than 50 kHz, the decline was obvious. When the frequency was more than 50 kHz, the decline was not obvious. Between 1 and 200 kHz, the relative dielectric constant of the egg decreased with the increase of the egg fresh degree. When the egg yolk index was less than 0.2, the relative dielectric constant decreased significantly. When the egg yolk index was greater than 0.2, the relative dielectric constant change was not obvious. We used MATLAB to fit the equation of relative dielectric constant and egg yolk index. Comparison of the determination coefficient, we found that the best fitting effect of measurement data under frequency of 1.2 kHz. The determination coefficient was 0.995. In order to test the correctness of the model, we randomly selected 50 eggs to measure. Validation of the results was that the determination coefficient was 0.9115 and the yolk index error within was ±4.2%. The results showed that the egg yolk index obtained by the fitting equation can predict the egg yolk index, which provided a new feasible method for the measurement of fresh degree of eggs.