Detection of intact egg eggshell quality based on NIR spectra

The quality of eggshell is an important factor on egg hatching, storage and transport. In this research, it was tried to detect the quality of eggshells with near infrared spectroscopy on the basis of eggshell quality indicator correlation analysis. Different spectral preprocessing methods and modeling algorithms were tested in different band ranges. The results showed that the best result was gotten with the partial least square regression (PLSR) modeling method at 5 characteristic wavelengths with the multiplicative scatter correction (MSC) preprocessing method. The quality indexes of the best modeling result were: 0.86(correlation coefficient, r), 4.42 N (root mean standard error of calibration, RMSEC) and 7.53 N (root mean standard error of prediction, RMSEP) for the relation between the eggshell strength and their spectra; 0.92, 0.313% and 0.529% for the relation between the eggshell percentage and their spectra; 0.81, 0.0176 and 0.0234 mm for the relation between the eggshell thickness and their spectra. The correlation between conventional eggshell quality indicators was studied. The result showed that the correlation is big between eggshell strength with eggshell percentage, egg specific gravity and eggshell thickness, the correlation coefficient were 0.55, 0.49 and 0.43, respectively. They are three parameters that closely related to the eggshell strength. And the eggshell strength can be characterized by them to a certain extent. The near-infrared spectra of different eggshell strength were compared. The result showed that the average spectral reflectance of the high-intensity group was biggest, the medium-intensity group is in the second place, and the low-intensity group is smallest. The result showed that near-infrared spectral characteristic was affected by the eggshell surface structure. In order to research the influence of eggshell internal structure on near-infrared diffuse reflectance spectra of eggs samples with different eggshell strength, the eggshell ultra-microstructure of samples was compared between groups of high and low eggshell strength. The result showed that with the increase of the eggshell strength, the eggshell cross-sectional consistency and smoothness became better, the mastoid layer and fiber layer related more closely and the effective thickness of the mastoid became smaller, the outer surface of eggshell became smoother and denser, and cracks reduced; the eggshell fiber layer structure became closer, the primary and secondary branch was clearer, fiber gap became smaller. All the results show that detecting eggshell quality using NIR spectra is feasible, and provides a new method for rapid non-destructive testing of eggshell quality.