Effect of Storage Conditions on External and Internal Quality of Table Eggs

Abstract

The shelf life of table eggs from poultry farm, open market and supermarket stored in the refrigerator, open shelf and cupboard for 21days were determined using standard microbiological and weight reduction techniques. The changes in pH, weight loss and bacterial load of the eggs were monitored as quality indices. Out of 216 eggs collected, only 24 (11%) were observed to be microbiologically spoilt. The bacterial isolates and their frequencies of occurrence were Micrococcus sp. 1(10%), Sarcina sp. 2(20%), Bacillus sp. 3(30%), Streptococcus sp. 1(10%), Staphylococcus sp. 2(20%), Salmonella sp. 1(10%) within the internal surfaces and  Micrococcus sp. 4(13.3%), Sarcina sp. 3(10%), Bacillus sp. 5(16.7%), Streptococcus sp. 3(10%), Staphylococcus sp. 8(26.7%), Salmonella sp. 2(6.7%), Flavobacterium sp. 1(3.3%), Corynebacterium sp. 2(6.7%), Proteus sp. 1(3.3%) and E. coli 1(3.3%) from the external surfaces respectively. Under the different storage conditions, the pH of the eggs were highly alkaline but progressively declined over the 21 days of storage. Similarly, there was a significant weight loss (p<0.05) over the storage period. Also, the microbial load on the external surface of the refrigerated eggs which was actually lower than those on the open shelf and cupboard differed significantly (p=0.05). From the correlation analysis, there existed a combined effect of pH and weight on the overall microbial load/quality of the eggs investigated. Eggs stored in the refrigerator over time generally recorded lower bacterial count and relatively no significant changes in weight loss and pH values. There was a positive correlation between the bacterial load and the storage time in all the samples. Refrigeration was therefore recommended as the best storage condition for eggs in order to increase their shelf life.