I couldn’t find definitive info on this. Having just arrived, I thought I’d let people know for the future.
I packed 2 bags of Huel in my hold luggage. I declared it as ‘food’ on the customs form. When questioned at Auckland, I explained that it was protein powder and he crossed it off my declaration. Then went through x-ray without an issue.
Just in case, I’d packed unopened bags so they could verify the contents and country of origin.