Definition and Analysis of Dietary Fiber in Grain Products
This chapter discusses the evolution of the definition of dietary fiber and the methodology to service this definition. Cereals are an important source of fiber in the human diet and therefore accurate analyses of the compounds that make up this dietary component are needed. The need to quantify the amount of carbohydrate that affects blood glucose levels led to methods to measure “available” carbohydrates and the recognition of the presence of “unavailable” carbohydrates, although no physiological role was assigned for this latter material. The term dietary fiber was introduced in 1953 and a physiological definition was introduced in 1976. A concerted effort was made to develop a method to service this definition through research. The outcome was the Prosky method (AOAC Method 985.29), which was accepted in 1985 as the gold standard method for the measurement of dietary fiber. As our understanding of the physiological importance of dietary fiber has advanced, it was realized that carbohydrates other than those measured by AOAC Method 985.29, namely resistant starch and non-digestible oligosaccharides, should also be included in the definition and measured and a new definition for dietary fiber was released by Codex Alimentarius. This definition includes resistant starch and the option to include non-digestible oligosaccharides. An integrated total dietary fiber (INTDF) method was developed in 2007 (AOAC Methods 2009.01 and 2011.25) and in 2015 was updated as a rapid integrated total dietary fiber method.