The Effect of Storage Time and Other Chemo-Physical Treatments on Peelability of Hard-boiled Table Eggs

Abstract

An experiment was conducted using a 285 fresh laid table eggs to study the effects of different levels of storage time and chemo-physical treatments (5% HCl, and 1% NaOH or both) and egg size on hard-cooked eggs peelability and/or weight. At first, 240 out of the total fresh laid eggs were divided into four experimental groups of approximately similar grades. Each group consisted of four replicates of 15 eggs. The table eggs in group one (control group) were subjected only to the effect of the storage levels (1-day, 7-days, 14-days, and 21-days) at room temperature then hard-cooked, weight and peeled manually. The table eggs in groups two, three, and four, in addition to the storage time were hard-cooked, weight and further subjected to the effect of 5% hydrochloric acid, 1% sodium hydroxide and combination of hydrochloric acid with sodium hydroxide respectively. At all levels of the storage time and treatments the hard-cooked table eggs were weighed and peeled manually. The peelability of each of the four egg groups was determined on the basis of a scoring system. The rest of the experimental eggs were graded and used to evaluate the role of egg size as a physical parameter on shell removal of hard-cooked table eggs. The results indicated that the peelability and the weight of the hard-cooked eggs were affected significantly by the different levels of the storage time. Hard-cooked eggs treated with acid alone and combination of acid with alkali showed the highest peeling scores during the different levels of storage time compared to the control group and alkali group. The alkali treatment showed low effect on the peelability of fresh laid hard-cooked eggs. This effect declined with storage time until zero effect was reached at 7th day. Chemical treatments showed no effect on egg weight. There was no correlation between peelability and egg weight. The sensory evaluation of all experimental eggs scored moderately desirable and above, in all measured attributes. Egg size had no significant effect on hard-cooked table eggs shell removal. In conclusion, the acid and acid-alkali chemical treatments have significant improvement effect on peelability of fresh laid eggs which in turn could preserve the quality characteristics of the hard-cooked table eggs.