Innovative packaging system for shell eggs storage: effects on egg quality traits and microbial loads

Shell eggs are breathable material and, after laying, allow moisture and CO2 to permeate through the eggshell, with a consequent sharp rise in pH especially in albumen. At the same time, several properties change, such as albumen whipping behaviour and foam stability. According to previous researches, modified atmosphere packaging (MAP) with high CO2 levels is very promising for shell egg quality traits maintenance, but the increase of the relative humidity in the package headspace, and the water condensation on the shell surface can promote microbe growth. The aim of this research was to study some quality modifications of eggs packed with different MAP active systems, during 28 days of storage at 21°C, with particular attention to physico-chemical (weight loss, pH, Haugh unit, colour) and microbiological traits (total microbial load). Fresh hen eggs were placed on plastic or carton supports and sealed in barrier pouches in air or in 100% CO2 MAP, with or without humidity absorber. The absorbing effect of the carton support and water absorbers was evident in terms of weight loss increase of packed eggs; as expected, the decrease of the relative humidity in the package headspace inhibited the microbes growth, with a maximum effect for eggs packed with the combined presence of carton support and water absorber. Eggs packaging reduced the pH increase and consequently the Haugh unit decrease. The greatest decline of egg quality was observed for not packed eggs, while eggs of all samples packed in 100% CO2 maintained about the initial values of Haugh unit for the whole storage period. The albumen pH of these samples was 1.5-2 points lower compared with the not packed product, for the whole storage period.