Why doesn't the protein in the egg white work to jell a custard?

Question

Answers to prevoius questions indicated that only an egg yoke will work not an egg white. Why?

Answer 1

Because the yolk thickens as it's cooked. The protein itself actually changes chemically. There is fat and cholesterol in teh yolk which "tempers" the denaturing (protein-changing) process and help yield a smooth, emulsified product.

You can use whole eggs (White + Yolk) in custards, but not whites alone.

Answer 2

Custard A liquid that is thickened or set by the coagulation of egg protein // this the deffintion of custard the protien is in the egg yolk wich is why that is the fat as well