Effect of Storage on Taste of Egg Albumen and Peelability of Hard-cooked Eggs

Abstract

It has been well known that peelability of hard-cooked egg is related to the storage condition, and that fresh egg is very difficult to peel. Recently, it has been maintained in Japan that albumen of hard-cooked fresh egg has sponge-like micro-structure, resulting in unfavorable taste.Fresh eggs, which were whithin 15min, on oviposition and were still warm by finger touch, were collected every mornining at 9:30 from the same flock of about 6-month-old White Leghorn hens. In Expt. 1, 10 fresh eggs and 10 eggs stored for 7 days at room temperature were compared. In Expt. 2, 40 eggs stored for 7 days at 23°C, 20 eggs each stored for 1, 2, 4, and 6 days at 5°C, and to fresh eggs were tested.The eggs were placed in water of twice in weight of the eggs in a pot, the water was brought to the boil, then putting out the fire the eggs were cooked for 15min. in the water. The eggs were cooled rapidly under running tap water.The ease of peeling was scored as follows: 1: no egg albumen adhering to the shell; 2: 1/4 of the shell covered with adhering albumen; 3: 1/2 of the shell covered with adhering albumen; 4: 3/4 of the shell covered with adhering albumin; 5: all of the shell covered with adhering albmen.The peeled eggs were sliced by egg slicers and egg yolk was taken off. In Expt. 1, three pieces of albumen, i, e., two of either fresh eggs or 7-day-stored eggs and one of the rest, were compared to find the odd one, and the panelists were asked whether the odd one was favorable or not. Eight sets of 6 panelists each, corresponding to 6 orders of arrangement of 3 pieces of albumen, were asked to test. In Expt. 2, taste of 3 pairs of albumen was compared separately by each of 49 panelists. The pairs were as follows: Eggs stored 7 days at 23°C (C egg) vs. eggs stored 2 days at 5°C; C eggs vs. eggs stored 4 days at 5°C; and C eggs vs. eggs stored 6 days at 5°C.By pH meter (Beckman zeromatic SS-3). pH of the albumen was determined individually after homogenizing genty for 10sec.Results were as follows:Among 48 panelists in Expt. 1, 37 (77%, P<1%) selected right albumen, of which 31 (65%, P<1%) pref ered albumen of the eggs stored 7 days to that of the fresh eggs. Number of the panelists who could find the difference in taste between pairs of albumen in Expt. 2, and number among them who prefered C egg albumen to that stored at 5°C are presented in Table 2. Percentage of the panelists who prefered C albumen was taken as an index of preference to show the difference in taste between pair of albumen. Highly significant correlation was observed between storage time (x days) and preference index (y %), as shown in Fig. 3. Linear relationship was also observed between storage time and peelability score. From these data, it was expected that an egg stored at 5°C will be easily peelable and have good taste of albumen after 9 days.Change in pH of albumen was curvilinear as shown in Fig. 3. Though it has been believed that egg shell will be easily peelable at pH of albmen higher than 8.6-8.9, pH of eggs easily peelable and having good taste of hard-cooked albumen was expected to be over 9.1.