Scope and field of application

 This method measures total available carbohydrates in food products, including cereals and cereal products, dairy products, fruits, vegetables, processed foods, food ingredients and animal foods. The method has been validated in a multi-laboratory study. “Available Carbohydrates” is defined as carbohydrates that are digested and absorbed in the human small intestine. Quantification of Available Carbohydrates is based on complete and specific hydrolysis of digestible starch, sucrose, lactose, maltose and isomaltose, with subsequent measurement of galactose, glucose and fructose.

References

-      ICC Standard No 101/2, Sampling of cereal grains.                               

-      ICC Standard No. 110/1, Determination of moisture content of cereals and cereal products (practical method).

-      ICC Standard No 130, Sampling of milled products.

-      ICC Standard No 138, Mechanical sampling of milled cereal products.

-      ISO 24333, Cereals and Cereal products - Sampling.

-      ISO 3696, Water for analytical laboratory use - Specification and test methods.

Definition

“Available Carbohydrates” is defined as carbohydrates that are digested and absorbed in the human small intestine. Quantification of available carbohydrates is based on complete and specific hydrolysis of digestible starch, sucrose, lactose, maltose and isomaltose, with subsequent measurement of galactose, glucose and fructose. Traditionally, available carbohydrates have been measured by the method of McCance and Lawrence (1929) which measures total starch, sucrose, lactose, maltose, glucose, fructose and galactose. Limitations of this method include the fact that total starch, rather than digestible starch is measured, and the use of a non-specific enzyme (invertase) for hydrolysis of sucrose results in the concurrent hydrolysis of fructo-oligosaccharides (FOS) and hydrolysis of the fructosyl residue from galactosyl-sucrose oligosaccharides, such as raffinose and stachyose. Furthermore, the method requires to sum data obtained from several analyses which is time consuming and increases the risk of errors. In the United States, the ‘by difference’ method for determining total carbohydrates was introduced by Atwater and Woods in 1896 and is still widely used. The moisture, protein, fat, ash and alcohol contents of a food are determined and then subtracted from the total weight of the sample and the remainder, or ‘difference’, is considered to be total carbohydrate. More recently, ‘net carbohydrates’ has been determined by subtracting dietary fiber from the total carbohydrates value. This value is meant to equate with ‘available carbohydrates’ determined directly, but the ‘by difference’ figure includes non-carbohydrate components such as lignin, organic acids, tannins, waxes and some Maillard products. Also, it combines all the analytical errors from the other analyses.