Purpose: This study investigated the feasibility of antibacterial coatings for controlling the microbial growth and improving qualities of fresh eggs stored at ambient temperature
Methods: Prior to coating application onto whole eggs, the antibacterial effect of prepared coating solutions (10% LYZ-3% CH, 0.5% cellulose nanofiber (CNF)-0.5% CH, and 0.5% CNF-0.1% OEO) was investigated against E. coli using agar-based disc diffusion method. Eggs were then coated by three coating solutions using an air-spray gun (~25-30 psi) and dried at the ambient temperature under an air-flow fan. Coated eggs were stored at ambient conditions (~25 °C) for 5 weeks. Total bacterial counts (TPC) and weight loss of whole eggs and egg grade were evaluated during the storage. Data were analyzed via analysis of variance (ANOVA) with the Tukey method (P < 0.05).
Results: The 10% LYZ-3% CH and 0.5% CNF-0.5% CH coatings significantly inhibited E. coli growth in comparison with 0.5% CNF-0.1% OEO coating. TPC of eggs coated with 10% LYZ-3% CH, 0.5% CNF-0.5% CH, and 0.5% CNF-0.1% OEO were 7.30, 11.34 and 11.98 log CFU/g egg after 5 week of storage, respectively, which was significantly lower than that of non-coated eggs (12.82 log CFU/g egg). Weight loss of coated eggs was also significantly lower (6.57-8.17%) than that of uncoated ones (9.18%) after 5 weeks of storage. The 10% LYZ-3 %CH coated eggs maintained B grade after 5 weeks of storage, but non-coated ones rapidly changed from AA to C grade within 3 weeks at ambient storage.
Significance: This study proved that lysozyme and chitosan based coatings can protect eggs from microbial contamination and improve internal freshness, thus extending shelf life.