USDA Pressure Chamber Makes Egg Microcracks Shine

A prototype pressure chamber and camera system that finds very small cracks, called microcracks, in fresh eggshells has been developed by Agricultural Research Service (ARS) scientists.

The device could help the fresh egg industry find microcracks that can often go undetected during grading, according to scientists at the agency's Egg Safety and Quality Research Unit (ESQRU) and Quality and Safety Assessment Research Unit (QSARU), both in Athens, Ga.

The ARS team that developed the device included food technologist Deana Jones at ESQRU and engineers Kurt Lawrence, Seung Chul Yoon and Bosoon Park, image analyst Jerry Heitschmidt, and technician Allan Savage at QSARU. Both units are part of the ARS Richard B. Russell Research Center.

The technology emulates human graders who squeeze the egg along suspected cracks to see if it opens. A prototype chamber was built that uses a brief negative pressure to slightly pull the eggshell outward to expose any existing cracks that may be present, without causing cracks in intact eggs. The camera system then takes a picture before and while the crack is opening to "see" if the shell is cracked.

According to Lawrence, the system detected 99.4 percent of eggshell cracks while recording almost no false positives--only 0.3 percent. In comparison, professional human graders had an 85.8 percent crack detection rate and 1.2 percent false positives.

Currently, many high-speed egg-processing plants use high-frequency analysis to "listen" for cracks, while other plants use human graders visually inspecting eggs with a bright light source in a low-light environment. But there hasn't been a reliable method for finding microcracks.

Microcracks are so small they can escape even the most experienced human grader's eye at the processing plant. Unfortunately, microcracks grow over time and are often easily visible by the time they reach consumers at market. Cracks are a safety concern, because they potentially create a pathway for pathogens such as Salmonella to enter the egg. The crack detection system would support the efforts of human graders to ensure high-quality eggs reach consumers.

Read more about this research in the February 2009 issue of Agricultural Research magazine.

ARS is the principal intramural scientific research agency of the U.S. Department of Agriculture.