Fiber (Insoluble, Soluble, Total - Gravimetric) Test

Method description

Samples (defatted if necessary) are digested with three enzymes (alpha-amylase, protease and amyloglucosidase) to remove starch and protein. Any solid particles not in solution after digestion are considered insoluble dietary fiber and are filtered off and measured gravimetrically. The filtrate from this first filtration is collected and ethanol is added to precipitate the soluble dietary fiber. The soluble fraction is then filtered and measured gravimetrically. All residues are corrected for ash and protein content. Total dietary fiber is calculated as the sum of the insoluble and soluble percentages.

Acceptable matrices

All foods and food products

Equipment

Standard Gravimetric Analytical Chemistry Equipment

Method reference

AOAC 991.43 with modifications

Reportable unit

%

Sample size requirements

40 grams

Information required by submitter

Please supply expected estimates. Indicate matrix type and indicate if samples are high in fat (>5%). Indicate whether the sample contains fructans (inulin or fructooligosaccharides (FOS)), or psyllium, flax and gum (i.e. guar gum).

Additional information

This test is ISO/IEC 17025 accredited through A2LA, Certificate # 2769.01.

Dietary Fiber is the portion of the carbohydrates which is not digested in the human gut. It is composed of both soluble and insoluble components. These methods are applicable to all food products, however samples containing psyllium or fructans should be submitted under specific test codes. High-fat (>5%) samples require special handling.