Effect of storage temperature on the quality of eggs from conjugated linoleic acid-fed laying hens
AbstractThis study was designed to investigate the effects of storage temperature on the quality of eggs from conjugated linoleic acid (CLA)-fed laying hens. For 40 days laying hens (20 per group) were fed a diet containing either 0.5% maize oil (Group A, Control) or 0.5% CLA (Group B). For fatty acid analysis, three eggs were collected after the eighth day of feeding. After two days of feeding, eggs were collected and stored for 28 days at 4°C, 15°C or 24°C for colour quality assessment. For pH measurements, 30 eggs from each group were stored at 4 C or room temperature (21-24°C) for one, two or three weeks. Dietary CLA caused higher levels of C16:0 and C18:0 and lower levels of C16:1(n-7) and C18:1(n-9) compared to the control group. Egg yolk from Group B had higher levels of c-9, t-11 and t-10, c-12 CLA than the control group. The ratio of total saturated to unsaturated fatty acids (SFA/UFA) increased 2.4-fold in the eggs from CLA-fed hens. CLA eggs stored at 4°C had higher pH values in yolk and lower pH values in albumen compared to those from the control group. However, pH values of yolk or albumen in eggs stored at 21-24°C were similar in the control and treatment groups. Dietary CLA caused significant colour changes in yolk and albumen of the eggs stored at 4°C and 15°C. No colour changes were observed in the yolk and albumen of CLA eggs at 21-24°C. Results indicated that dietary CLA influenced fatty acid composition of eggs and had negative effects on the quality of eggs stored at 4°C or 15°C, but not at room temperature (21-24°C). It is suggested that CLA probably changed the permeability of the vitelline membrane during cold storage.
South African Journal of Animal Science Vol. 36(1) 2006: 13-19