Dietary fibre analysis in high starch containing products: modification of the AOAC 2009.01
and 2011.25 methods

By Yannis Vrasidas, Eurofins Food Testing Netherlands, Carbohydrate Competence Center

Dietary fibre (DF) analysis is a very important analyte for the food industry. Nowadays DF is generally accepted as an essential part of the human diet. Chemically, DF consists of nonstarch polysaccharides and/or other components including resistant starch, inulin, pectins and ß-glucans. Various analytical methods for the quantification of total DF, and/or its individual components, are known and widely used. It is understandable that following the developments and needs of the analytical & nutrition research community and industry, it may be necessary to change and/or improve established methods.

Brunt and Sanders from Eurofins' Carbohydrate Competence Centre (CCC) identified a shortcoming in the AOAC 2009.01 and 2011.25 methods for high starch containing products e.g. bread or pasta. The methods include, as an initial step of the analysis, an enzymatic treatment in order to remove starch and maltodextrins from the sample as those components are not considered as DF. The team observed that, for those matrices, starch and maltodextrins were not fully hydrolysed and completely removed from the sample. This incomplete hydrolysis results in amounts of about 0.5 - 1.5% residual digestible maltooligosaccharides that are erroneously counted as DF. For various types of bread and pasta an overestimation of 0.5 - 1.5% in DF can be decisive for the use of the dietary claim "source of dietary fibre" or "rich in dietary fibre".

In order to eliminate this over-estimation, the Eurofins' CCC team developed a modification of the methods by introducing a second enzymatic hydrolysis within the analytical protocol. Their findings were published¹ and were independently confirmed by two other groups (B.V. McCleary (Megazyme) and W.D. Park (Texas A & T University)). In December 2013 the improvement for high-starch containing matrices was adapted by AOAC and a revision of the AOAC 2009.01 and 2011.25 methods has been published.

Eurofins offers to its clients, among a large variety of official DF methods, both revised methods and routine tests.

Contact: carbohydrates@eurofins.com

¹   K. Brunt, P. Sanders Food Chemistry 140 (2013)  574-580