Effect of different cooking time on the textural profile and lipid composition of hard-boiled egg

In present study,fresh eggs which were boiled in water for 10,15,20 and 25 min were used and analysis methods including water content,water T₂ relaxation time distribution,texture of egg white and egg yolk as well as the lipid composition of egg yolk were established,with the aim at systematically investigating the effect of different boiling time on the texture of boiled eggs and nutritional components in lipid. The results showed that,the gel structure of egg white and egg yolk were completely formed after 15 min and 20 min boiling,respectively. The amount of bioactive lipid components in egg yolk such as phosphatidylcholine(PC),phosphatidyl ethanolamine(PE),phosphatidyl hexanol(PI),phosphatidic acid(PA),phosphatidyl glycerol(PG)and ceramide(Cer)were highest in samples boiled at 15 min,while the content of sphingomyelin(SM)was highest in samples treated with 10 min boiling and decreased when boiled till 15 min. The amount of total monounsaturated fatty acids(∑MUFA)was significantly increased during the first 15 min boiling(p<0.05)but was not significantly changed by further boiling. The amount of total polyunsaturated fatty acids(∑PUFA)was not significantly changed by the first 15 min boiling but was significantly decreased with the extended boiling time(p<0.05). The results showed that,the texture of boiled eggs and nutritional components in egg yolk lipid reached the best level when treated with 15 min boiling. And these findings would provide theoretical basis forindustrial production of boiled or stewed eggs for breakfast in China.