What is this white foam when I boil my chicken?

Can someone please help me out? Ive been observing this for the last few times.

Is it fat?

The chicken is not expired and it isn’t close to expiry and was frozen before cooked.

Can someone please help me out? Ive been observing this for the last few times.

Is it fat?

The chicken is not expired and it isn’t close to expiry and was frozen before cooked.