Improved Modified Pressure Imaging and Software for Egg Micro-Crack Detection and Egg Quality Grading

Abstract

Cracks in the egg shell increase the food safety risk. Eggs with very fine, hairline cracks (micro-cracks) are often undetected during the grading process because they are almost impossible to detect visually. A modified pressure imaging system was developed to detect eggs with micro-cracks and regular cracks alike without adversely affecting egg quality. The modified pressure imaging system forces a change in pressure from the atmospheric pressure to the negative pressure (vacuum) in an enclosure to open the cracked shell surface momentarily, while intensity changes in the open shell surface are recorded by a high-resolution digital camera and detected by an image processing algorithm. In this article, modifications and improvements to the system are reported along with application software development. The previous design for 15 eggs was modified to accommodate 20 eggs and improved to add a stepper motor to image the entire surface of eggs automatically and the data management software was added to aid a professional grader in egg grading. In a three-day study with 3,000 eggs in a commercial egg processing plant, a professional grader operated the 20-egg imaging system after a short training on the first day and another professional grader graded the eggs with hand candling. The accuracy in crack detection of both graders and the system itself was compared in order to test the crack-detection performance of the system and to explore the possibility of the use of the system for egg grading by USDA graders. The system automatically detected checked and cracked eggs with 94.53% accuracy with 0.29% of a false positive rate while a hand candler had 83.58% accuracy in crack detection. The grader operating the system had 98.51% accuracy in crack detection without any false positives. Other quality factors were also graded by both graders. The study demonstrated the potential of the system for egg grading in high accuracy.