Antimicrobial lysozyme-chitosan coatings affect functional properties and shelf life of chicken eggs during storage.

BACKGROUND: The interior quality, shell impact strength and functional characteristics of eggs coated with chitosan and lysozyme-chitosan combinations were evaluated for enhancing egg freshness during storage. A 10% (w/w) lysozyme solution was incorporated into 1% (w/w) chitosan film-forming solution at ratios of 0, 10, 20 and 60% (w/w).
RESULTS: Storage time and coating had significant effects on Haugh unit, yolk index, weight loss, albumen pH, dry matter, relative whipping capacity (RWC) and albumen viscosity. Uncoated eggs had higher albumen pH and weight loss and lower albumen viscosity. All coated eggshells showed greater puncture strength than uncoated eggshells, resulting in extended shelf life. The 20 and 60% lysozyme-chitosan coatings were more effective in maintaining the internal quality of eggs (e.g. pH, dry matter and RWC). Attributes such as pH, dry matter and RWC were better after the 20% lysozyme-chitosan treatment than after the other treatments.
CONCLUSION: The 10, 20 and 60% lysozyme-chitosan coatings, considered active packaging, showed promising attributes. They could be a viable alternative to existing techniques for maintaining the internal quality of fresh eggs during long-term storage. Chitosan coatings also improved shell strength. This study also confirms that measurements of albumen quality (pH, dry matter, viscosity and RWC) are excellent indicators of egg freshness.