Question: What is the Halachic status of milk powder (avkat chalav) manufactured from milk that is cholov akum?
Discussion: The prohibition of cholov akum is clearly delineated in Shulchan Aruch Yoreh De’ah Siman 115.
Some claim that this prohibition was specifically enacted regarding (liquid) milk, however, milk powder is a different entity to (liquid) milk, and even if the same reasons that apply to milk should apply to milk powder, ultimately Chazal never forbade unsupervised milk powder, and thus it should be permitted to eat.
However, there is a proof from a different siman in Yoreh De’ah that refutes this claim: The Shulchan Aruch rules (Yoreh De’ah Siman 97) that it is forbidden to bake milky bread – unless one only bakes a small quantity of bread or shapes the bread into an unusual shape. Ex post facto, if a regular quantity of milky bread was baked in the regular shape, the bread is forbidden to be eaten.
The Pischei Tesuva quotes the Chavos Da’as who posits that if a regular quantity of bread was baked in the regular shape, it is not possible to change the shape of the bread after it is baked (e.g., to cut the bread into unusually shaped slices) because at the stage of baking the bread becomes forbidden, and once the bread forbidden the prohibition remains on the food item, even if the reason for the prohibition no longer applies.
Therefore, returning to our situation, cholov akum is unanimously forbidden. Even if it can be argued that Chazal only forbade (liquid) milk when it is cholov akum and never forbade milk powder, since the milk which is used to make milk powder has been forbidden because of cholov akum, the prohibition remains even if the milk is changed into another form.
Answer: Milk powder that originates from cholov akum has the same status as liquid cholov akum and it is forbidden to eat/drink.