Studies on the Keeping Interior Quality of Chicken Eggs

Abstract

From the food hygienic point of view, we have investigated on the problems of lipid peroxidation and migration into edible part (albumen and yolk) of edible vegetable oils coated to egg shell.The peroxide values were measured colorimetrically for lipids from shell with shell membrane and the edible part of eggs coated with five kinds of edible vegetable oils, which were prepared from a palm oil and a safflower oil which were subjected to fractional distillation, and from a coconut oil, as three kinds of a palm oil and safflower oil mixtures supplemented with 0, 150, and 300ppm of α-tocopherol, a coconut oil, and a palm oil, coconut oil and safflower oil mixture. The coated and uncoated eggs were held in a box at a room (temperature: 25-31°C; relative humidity: 60-93%) for 5 weeks in summer, and the peroxide values were determined weekly. The peroxide values of lipids from shell with shell membrane of the coated eggs ranged from 1.3 to 6.7meq/kg among the five kinds of oils used through storage period for 5 weeks. The corresponding figures for the edible parts gave less than 0.4meq/kg, while the edible part from the coated eggs tended to have peroxide value a slightly higher than that from the uncoated eggs from 2nd week through 5th week, with the latter remaining at about 0.1meq/kg.The migration amount of the palm oil and safflower oil mixture, which has a radioactivity of 2, 890cpm of carboxyl-14C-tripalmitin per mg, into the edible part have been investigated next. The coated eggs were held in a room (temperature: 14-28°C) for 60 days in early summer, and the respective radioactivities for the portions of egg shell, shell membrane and edible part (albumen and yolk) were measured. The migration amount of carboxyl-14C-tripalmitin into the edible part ranged from 0.07 to 0.39% of the amount (about 52mg) used for coating egg shell, but most of the radioactivity remained in egg shell and shell membrane. The obtained migration amounts of carboxyl-14C-tripalmitin in this experimnent were found to be about one-twentieth to one-tenth of the migration amount for mineral oil (liquid paraffin) reported in the literatures.