Both whey protein concentrate (WPC) and whey protein isolate (WPI) generally classify under 040410 as modified whey products, provided they are derived from whey and have not been so extensively processed as to lose their character as a milk constituent product. However, highly processed whey derivatives used primarily as food additives may migrate to other chapters. The protein content, processing method, and intended use should be reviewed against the heading text and any applicable CBP rulings.

Heading 0404 covers whey in its various forms and other products consisting of natural milk constituents (such as milk protein concentrates). Lactose — the milk sugar — classifies separately in the sugars chapter, and casein (the principal milk protein used in industrial and food applications) has its own heading in the chapter on albumins and proteins. When a product is a blend or has been fractionated, the predominant constituent and the degree of processing determine which heading applies.