"She buys one kilogram of potato in total."
Translation:Ela compra um quilo de batata no total.
While I understand why this is translated as is, I don't think at least in the US we would ever use the singular for potato in this context. Rather, we would say "She buys a kilo of potatoes in total." I think the only time we would refer to a potato in singular was if we were speaking of a specific potato (e.g., please give me that potato) or the potato as a type of food (e.g., the potato originated in the Americas).
I agree totally that it would never be 'kilo of potato', at least in the US! My question is, if it had been stated 'one kilo of potatoes' would the Portuguese still be 'um quilo de batata' or 'um quilo de batatas'? How would you ask the question if you walked into a Portuguese grocery?
My co-op (cooperatively owned grocery) that I used to go to – before moving as otherwise I would still go – had several organic dried soups we could buy in bulk. One of them was a potato soup mix. They also had dried potato flakes which would make instant mashed potatoes. I think they may also have had just dehydrated already peeled and cut potatoes (like processed food mixes such as Hamburger Helper use, only better and organic). We also could bring our own containers in for filling.
So I could actually see this use. What kind of the soup mix does she buy each time? She buys 2 bulk bags of potato which together [in total] weigh 1 kilo.
Or, what kind of salad does he buy? He likes potato, and buys 4 containers which together [in total] weigh one kilo.