This Is AuburnElectronic Theses and Dissertations

Safety and Quality of Non-Commercial Shell Eggs




Santos-Norris, Geraldine

Type of Degree

PhD Dissertation


Poultry Science


The market for non-commercially sourced shell eggs has primarily been driven by consumers’ perception of higher safety and quality. Due to the marginal availability of data on these eggs, the objective of this study was to evaluate the safety and quality of non-commercial shell eggs to provide data to its current state, as well as establish a baseline for reference. Convenience sampling of shell eggs were derived from small/backyard flocks, small farms, community farms, farmers markets, and/or health food stores. Safety evaluation focused on microbiological (specifically, Salmonella spp.) and chemical (specifically, lead and arsenic) as a potential hazard. For detection of Salmonella spp. (n=1,388) (isolated by FDA BAM culture methods and confirmed through PCR), 3 positive samples were identified, which suggests that the risk of Salmonella is higher in shell eggs from non-commercial sources compared to those produced by commercially caged hens (1 in 20,000). In a rural backyard flock case study, composite eggs (yolk and albumen) analysis (n=36)(ICP-MS) indicated lead and arsenic concentration ranges from <0.02 ppm to 0.05ppm and <0.02 ppm to 0.04 ppm, respectively, where environmental soil analysis (ICP-AES) indicated lead and arsenic detection at 1,835 ppm and 6 ppm, respectively. The presence of lead and arsenic from this case study, suggests a potential public health concern from non-commercial shell eggs. With quality evaluation, yolk color data (n=1,118) was conducted with a novel digital yolk colorimeter (Digital YolkFan™) and indicated an average of 9.0. Haugh unit (HU) data (n=1,273) indicated an average of 75.24 HU. Based on collected HU values and equivalence to USDA grading, approximately 65% of all samples evaluated were Grade AA, 25% were Grade A, and 10% were Grade B or less. Average shell strength (n=1,273) was observed at 3,939 g Force, which is within the average range of commercially produced brown and white eggs. Average vitelline membrane strength (n=1,191) was observed at 122.79 g force, which is below previously evaluated commercial eggs that underwent extended storage. Overall, the quality of shell eggs from non-commercial sources can vary from comparable to retail markets to well below. Finally, non-commercial shell egg suppliers are varied in their flock management and egg handling practices (egg collection frequencies, egg washing, and storage/transport conditions). These variances can contribute to the quality and safety of shell eggs, and is important to consider as a consumer to understand the potential impact to the shell eggs being purchased/obtained.