The vernix caseosa was not removed. It's normal fetal bovine serum
Q2: What are the precipitates in the serum? Why do they look different between batches?
The flocculent substances in serum are usually normal fibrin precipitation. The fibrinogen content in the blood of different animals or individuals varies, which may lead to different degrees of fibrin precipitation in different batches of serum after thawing, but it does not affect the normal use of the product.