This is a scientific study on the effects of storage of eggs and quality and nutrition. In short, under 2 weeks, out of refridge and kept under 75 degrees in pantry is just fine. Oiled eggs, stay nutritious the longest, the icebox comes in second. In our opinion, the best freshest eggs are those used within 1-4 days of laying-- Own your own hens, in other words.
In tropical countries like Nigeria, egg preservation is a serious problem. The common practice is to store under ambient condition due to lack of refrigeration facilities and erratic power supply. Four crates of fresh table eggs were bought from the University of Agriculture, Makurdi farm and preliminary investigations of egg weights, Haugh unit, pH and yolk index were carried out before storage and found to be within standard. Thirty eggs were stored under ambient condition with and without application of oil respectively. The other group of thirty eggs was refrigerated. The initial weights were in the range of 60 – 69 g which reduced drastically. All other quality indices like the Haugh unit, the yolk index and pH declined drastically within the four weeks of the storage especially those that were stored under the ambient conditions. Those stored under refrigeration and those that were oiled and stored under ambient conditions (32 + 2 °C) maintained high quality standards in all the quality indices evaluated. The microbiological result also showed higher bacteria, yeast and mould count on those stored under ambient condition with the initial count of 5.0 × 103 at first week and 2.8 × 107 at the fourth week while the oiled and refrigerated eggs had values of 5.0 × 103 at week zero and 7.2 × 104 at week four of storage respectively. It is suggested that application of oil on eggs before storage can be practised to ensure retention of good quality eggs especially in the tropics and most developing nations of the world.
Eggs are laid by females of many different species, including birds, reptiles, amphibians and fish but the most often consumed by humans is the chicken (Table) egg (Wikipedia, 2012). Chicken eggs provide a well balanced source of nutrients for man of all ages. Chicken egg, whole and hard-boiled, contains 12.6 g/100 g protein, 10.6 g/100 g fat, 1.12 g/ 100 g carbohydrate and 647KJ (155Kcal)/100 g energy. Due to the protein content, the United States Department of Agriculture (USDA) categorised eggs as meats within the Food Guide Pyramid (Howe et al., 2004). Eggs are declared as A (Jumbo) quality must have at least 72 Haugh Units, eggs of B (Extra large) quality must have more than 60 Haugh Units and eggs with Haugh Units lower than 30 are not for consumption as a shell egg (Faris et al., 2011). Chicken eggs consist of a protective egg shell, albumen (egg white) and vitellus (egg yolk) contained within various thin membranes. Egg shells act as hermetic seals that guard against bacteria invasion (Wikipedia, 2012) and the shell membranes function to retain the fluid of the albumen and also to resist bacterial invasion (Hassan and Aylin, 2009). A young hen produces eggs with thicker shells and longer pores than older hens. The egg shell colour is caused by pigment deposition during egg formation in the oviduct and can vary according to species and breed (USDA, 2011).
All foods have a limited shelf life which will vary depending on the food and storage conditions. Eggs are very perishable food products. Careful preservation of edible eggs is extremely important as improperly handled eggs may contain elevated levels of Salmonella bacteria that can cause severe food poisoning, hence the USDA recommends refrigerating eggs in order to prevent the growth of Salmonella (Wikipedia, 2012). The application of coatings on eggs, on the other hand, can be justified since they maintain the functional properties of food by decreasing moisture loss and gas transport (oxygen and carbon dioxide), hence the application of coating on eggs reduces weight loss and maintains internal measurement such as albumen and yolk (Nadia et al., 2012). Though oiling of eggs is very effective in slowing down reduction in albumen and yolk quality, it does not replace the need for cool storage (Faris et al., 2011). The internal quality of eggs starts to decline as soon as laid by hens (Roxana and Usturoi, 2012). The major difference between freshly laid eggs and stored eggs are albumen pH and albumen quality (Albumen height) (Nadia et al., 2012). Albumen quality, a standard measure of egg quality, is influenced by genetic and environmental factors such as temperature, time and humidity of storage (Roxana and Usturol, 2012).
Egg handling and storage practices have a significant impact on the quality of eggs reaching consumers. Read the rest