Improved Hairline Crack Detector and Poor Shell-Quality Eggs

Abstract

As more egg processors are moving to in-line processing facilities, human egg graders are having difficulties detecting small hairline-cracks in table eggs. These small hair-line cracks are much harder to detect than larger or older cracks. To aid graders, a modified-pressure imaging system was developed to detect cracks in table eggs. The original system was modified and can now process 20 eggs at a time in batch mode. The eggs are positioned on rollers and held in a sealed clear acrylic chamber. The system utilizes high-intensity white LED lights for illumination and a stepper motor is now used to automate the rotation of the eggs. It also uses a high-resolution monochromatic camera to take images of the eggs. The first image is taken at atmospheric pressure and the second is taken while the chamber undergoes a short, rapid, negative change in pressure. If there is no crack, then there is effectively no difference in the two images. However, if a crack is present, it causes an increase in the intensity of the crack pixels in the negative-pressure image resulting in a significant difference between the two images. This difference (in the form of a ratio) is the basis for identifying a crack. Software then displays the egg images and color-codes each egg as either green (intact) or red (cracked) and highlights any cracks with a contrasting color. Typically, the system uses four sets of images to cover practically all the eggs surface and completes the crack detection in about 40 s. The modified system was tested with poor shell-quality eggs from multiple strains of hens to see if it would induce cracks in these eggs. Analysis of 3279 poor shell-quality eggs (both white and brown), from six strains of pre-molt hens, laid in the heat of the summer, resulted in only one crack caused by the system (0.03%). Thus, it is highly unusual for the system to cause cracks in intact eggs, even eggs with poor shell quality.