Effects of emulsion coatings on the internal quality and shelf life of eggs

Abstract

Mineral oil (MO) is currently used for coating eggs to preserve quality. Chitosan possesses inherent antimicrobial and film-forming properties. Chitosan coating (CH) is dried much faster than MO when applied on egg shell. Information on synergistic effects of MO:CH emulsion coatings on egg quality does not exist. We developed MO:CH emulsion coatings, and evaluated their effects on internal quality and shelf-life of eggs during storage. In the first study, MO, CH and three emulsions (MO:CH = 75:25, 50:50, and 25:75) were evaluated during 5 weeks at 25°C. Haugh unit (HU) and yolk index values decreased whereas weight loss increased during storage. Noncoated eggs changed from AA to C grade after 3 weeks. However, all emulsion-coated eggs maintained an A-grade for 4 weeks. All emulsion-coated eggs had weight losses <1.5%. Only 25:75 MO:CH emulsion-coated eggs were not sensorially glossier than noncoated eggs. All emulsion-coated eggs had >80% positive purchase intent and were negative for Salmonella spp. In the second study, 25:75 MO:CH emulsions prepared with four different emulsifier types were evaluated during 5 weeks at 25 °C and 20 weeks at 4 °C. All emulsion-coatings minimized weight loss (<1.5%) and preserved internal quality of eggs for at least 3 weeks longer than observed for noncoated eggs at 25 °C. At 4 °C, all coated eggs changed from AA to A grade after 5 weeks and maintained this grade up to 10 weeks with weight losses <2% at refrigeration. The emulsifier type generally did not insert significant effect on the internal quality. In the third study, MO and 25:75 MO:CH emulsion were evaluated during 5 weeks at 25°C using eggs from three different albumen qualities, expresed as HU, before coating: ‘High’=87.8 HU, ‘Medium’=75.6 HU and ‘Low’=70.9 HU. MO and/or 25:75 MO:CH coatings could preserve the internal quality for at least 4 more weeks for ‘High’ HU eggs; all with weight losses <0.92%). This study demonstrated that MO:CH emulsion coatings could preserve the internal quality of eggs and prolong their shelf life.