So what exactly is tomato puree? When i look for tomato based products i dont see any saying puree.
As I said in my previous post, it's tomato concentrate. Basically passata (sieved tomatoes) which has been boiled down to a very concentrated form. It usually says on the tube "Double Concentrate" Here:
http://www.bbc.co.uk/food/tomato_puree that's what it looks like. Here's a tube:
http://www.tesco.com/groceries/Product/Details/?id=254879475Please don't confuse
tomato puree with with pureed (you can see where the confusion comes in) or
blended plum tomatoes - they're quite different things. The most important of which is that one has had virtually all its water removed (puree) and is in a very concentrated form and one still has a lot of water still in it - blended plum tomatoes.
The major difference between them in terms of BIR cooking is the amount of reduction you'll need to do to remove the water elements. The reason tomato puree is mixed with water prior to being added is because if you add puree direct to hot oil, it will burn and stick to the bottom of the pan very quickly. By diluting tomato puree with water, you gain more control over exactly when all the water has evaporated, the oil separates and you start to get slight caramelisation of the puree sugars as it starts to turn a darker shade. This shade darkening is caramelisation.
The purpose then of puree rather than blended plum tomatoes is the slight caramelisation of the puree sugars, the dark red/brownish colouring and texture.
You cannot achieve all of those things with blended tomatoes.