How do you measure starch on a food label?

Answer 1

You cant, under the current US labeling regulations. The issue most concerning is the gluten allergy problem, and the "modified food starch" problem, that can be made from wheat and containing gluten.

Only the top eight food allergens are reqired to be listed on the label in ingredients, but even then, often they are disguised.

Answer 2

There is usually not much starch on a food label and so this would be difficult to determine.

I presume you mean you want to know how to determine how much starch there is in a food product in order to compare with what is on the packet's label?

There are a number of methods which depend on the starch. Starch it self is a complex molecule as I am sure that you are aware. Some methods determine the numbers of functional groups while other use oxidation of the aldehyde groups. One method is to use spectroscopy to determine the light absorption of the colour developed between iodine and the carbohydrate.
Some carbohydrates (such as sugars in syrup) are determined by high perfromance liquid chromatography.

Answer 3

As Bob says this is a complex problem. Quite often you will see on a label something like ("carbohydrate xx g of which yy g as sugars"), while on others they may give you a figure (often as %) for the starch content. The latter may or may not be defined further as 'maize starch' or 'modified starch' for example.

The gluten issue is well know to me as I am a coeliac.

In Eurpope the position is slightly different to that in the US. The new European labelling legislation came into force in November 2005.

The following 12 allergens, where present, are required to be declared on the label of food/drink products:

Tree nuts, peanuts, sesame seeds, mustard, celery, fish, shellfish, soya beans , cereals containing gluten, eggs, milk, sulphur dioxide and sulphites at levels above 10mg per kg or per litre.