Regular Paper

Evolution of a Definition for Dietary Fiber and Methodology to Service This Definition

Barry V. McCLEARY, Jodi COX

Megazyme, Bray Business Park, Southern Cross Road, Bray, County Wicklow, Ireland.

The definition of dietary fiber has been evolving over the past 70 years. The changing definitions reflect our better understanding of the types and physiological functions of dietary fiber. Initial definitions focused on “the remnants of the plant cell walls which are not hydrolyzed by the digestive enzymes of man” and appropriate analytical methods were developed and implemented. More recently, the role of resistant starch and non-digestible oligosaccharides (NDO) as dietary fiber components has been recognized. Incorporation of these has required the development of a host of other methodologies to measure specific dietary fiber components such as fructo-oligosaccharides, galacto-oligosaccharides, resistant maltodextrins, resistant starch and others. Having these specific methods is useful for product manufacturers, but not necessarily for regulators because some of the specific component may also be partially measured by the “gold standard” fiber method, the Prosky method (AOAC Method 985.29). It is thus not possible to simply sum the various specific components with the value obtained with AOAC Method 985.29, as this will lead to “double counting” and thus overestimation of fiber content. To resolve this problem, and allow measurement of all dietary fiber components, an integrated method for measurement of total dietary fiber (AOAC Method 2009.01/AACCI method 32-45.01) was developed and adopted. Evaluation of this method over the past 8 years identified some aspects of the method that could be improved. Modifications have been made and incorporated into a Rapid Integrated Total Dietary Fiber (RINTDF) method, and this method has been subjected to interlaboratory evaluation under the auspices of ICC International and AACC International.