Dear Amit,

Currently two different AOAC methods are described for the analysis of FOS and inulin in foods, being the AOAC 997.08 and the AOAC 999.03.

Methods of analysis.

Both analytical methods for inulin/FOS have typical different fields of application in the analysis of (food) samples. The different underlying principles of analysis are the reason that there is not one ‘golden standard’ method. It is necessary to choose

the best method for different matrices. The principle and the pro’s and contra’s of both methods are described here. At the end of this brochure, advice is given for choosing the best method.

Method 1 AOAC 997.08

In this method first the free fructose and free sucrose content are quantified. In the next step after enzymatic conversion of starch and maltodextrins, total glucose is measured. The last step includes total conversion of inulin/FOS and sucrose into glucose and fructose and analysis of these components. After three high performance anion exchange chromatographic (HPAEC-PAD) measurements the inulin/FOS content is calculated by subtracting the glucose, sucrose and fructose contents as measured in step 1 and 2 from the total fructose and glucose content as measured in step 3. This implies that large corrections have to be made for samples containing large quantities of fructose, glucose, sucrose, maltodextrin and/or starch. Subtraction of two large values in order to calculate much lower inulin/FOS values generally results in less precise data with a large standard deviation. The advantages/disadvantages of this method are summarized in the tables below.

Method 2 AOAC 999.03

The principle of this method differs from AOAC 997.08 in that here all

monosaccharides present after the combined amylases and sucrase treatment

are removed by converting them into alditols (borohydride reduction). So, also samples with high contents of monosaccharides, sucrose, maltodextrin and/or starch can be accurately measured in this procedure because subtractions are not needed. The standard methodology of end point measurement is colorimetry (total of reducing sugars present after inulinase treatment). Eurofins applies, like in AOAC

997.03, HPAEC-PAD, since this is specific for glucose and fructose and not hindered by turbidity, which is characteristic for e.g. dairy samples. However, there is a major drawback in this method since also the reducing end groups of Fm molecules are reduced into alditol and so these end groups escape analysis. This

implies that recovery of difructose (F2) is only 50%, for F3 67 %, for F4 75% etcetera. GFn molecules do not have a reducing end group, so these are recovered completely. FOS material prepared by depolymerization of inulin contains in general high amounts of F3 and F4, so total recovery will be about 80% or even lower for these preparations.

For more details, please use the following link:

http://www.dietaryfibretesting.com/media/4304392/Which_Carbohydrate_Testing_method_to_use.pdf

Rafik