A Poultry CRC research project is being undertaken at the University of New England, Australia (UNE) to examine how defects in shell quality and structure increase the risk that bacteria on the outside of the eggshell can enter the egg.

Sub-Project Leader, UNE's Associate Professor Juliet Roberts, said that, essentially, the Australian egg industry produces a very safe product.

"Australia is fortunate in not having a problem with Salmonella Enteriditis in its layer flocks, as is the case in North America and Europe," explained Associate Professor Roberts. "However, Salmonella Typhimurium causes problems with food-borne illness from time to time and some of these occurrences have been traced to the consumption of eggs. For this reason, the industry needs to be vigilant in monitoring the impact of food borne pathogens such as Salmonella in eggs and egg products."

The project will investigate the incidence and significance of minor defects in the ultrastructure of the eggshell, such as translucency, which is where lighter colour spots are observed when an egg is candled over a light source. These spots appear when moisture from the egg albumen seeps into spaces within the fine structure of the eggshell, but they are difficult to detect in very fresh eggs.

"There is some evidence that translucent regions of the eggshell are more easily penetrated by bacteria than areas which are not translucent," said Associate Professor Roberts.

Another feature of eggshells that will be investigated is micro cracks, which are very small fine cracks not visible to the naked eye and which can be difficult to detect by candling, particularly in very fresh eggs. Micro cracks have the potential to facilitate the entry of bacteria into the egg.