Don’t know the percentage of the top of my head, but milk powder (or casein derived from milk powder) is used in paints, paper manufacturing, textiles, it’s used a an ingredient for a whole bunch of things in labs, packaging, an additive to some plastics, in some places an additive to concrete, it’s used in cosmetics. Whey is used to produce industrial alcohol (Fonterra used to make this, don’t know if they still do). It’s got a lot of non-food related uses.

I submit that Fonterra does know the percentage. It's their business to know it. You don't know the percentage and therefore are in no position to criticise them for going after a market which may in fact be tiny compared to milk for human consumption.

And even in the food industry, corporations like Nestle aren’t going to care where it comes from when they’re using it to adjust fat or protein content in the vast majority of their foods.

They will if it effects the taste.