Maize starch vs cornflour

What is the difference?

I do get people asking that question from time to time. The short answer is maize starch is the same as corn flour made from corn (like the photo of my yummy backyard produce). Cornflour from corn = maize starch and is very low in protein (~0.3 g/100 g). In other countries corn can mean the locally grown crop (confusing the issue even further) so it might not be maize.

The non wheaten corn flour sold in the supermarkets is actually maize starch.

Remember cornflour available in most supermarkets can also be made from wheat. In this case it really is wheat starch. Check the labelling for the source of the starch.

Starch vs Flour?

The labelling of starches/flours is a little confusing - & there seems to be no rhyme or reason. Technically a flour should contain protein, carbohydrate, any fat & any fibre available from the grain/nut etc. that is being ground & a starch should just have the carbohydrate. The potato starch you can buy in the supermarket is labelled potato flour (check the nutritional panel for the protein content) but has no protein (so it's really a starch).

In most cases potato flour = potato starch, like maize starch it has very little protein (<1 g/100 g).

Adding on to the above I have seen tapioca flour (with no protein content) at 5x the price of tapioca starch (also no protein content). Cassava flour contains tapioca starch with ~1 g of protein/100 g. 

If you are unsure whether the product is a starch or not check the nutritional information. If the product has less than 1 g of protein per 100 g the product is a starch.

Why add starch?

Like protein, starch is essential for baking (whether that be gluten free or containing gluten). For example starch can help with the structure of the product, it can be used to 'soften' the product, it can be used to lighten the product & to minimise the effect of gluten on the product.

Some people will throw up their hands in horror at the amount of starch added to a gluten free product & will aim to buy products that have no added starch. That is not necessarily better as the flour used may have minimal protein eg. cassava flour or green banana flour & be mostly starch. It really depends on the amount of starch & protein added to a specific gluten free blend.

As a point of reference if a packet of wheat flour was labelled with its constituents it would look like this;

Wheat starch 70.5%, wheat protein 9.7%, dietary fibre 2.8%, sugar 1.8%, fat 1.6 % & salt.