Analysis of Dietary Fiber in Feces of Rats Fed with Fiber Supplemented Diets

Abstract

A procedure based on Southgate's fractionation scheme with subsequent calorimetric determination of monomeric constituents in the individual fractions was used for the analysis of feces of rats fed with diets supplemented with cereal bran or its fiber components. Prior to fractionation, dehydrated feces were extracted with chloroform:methanol (2: 1) mixture and hot 80% methanol and then subjected to treatment with both amylolytic (MERCK glucoamylase, 6O"C, 2 hr) and proteolytic (CALBIOCHEM pepsin, 4O"C, 48 hr) enzymes. Calorimetrically determined values of noncellulosic polysaccharides and cellulose (calculated as sums of hexoses, pentoses, and uranic acids) agreed satisfactorily with those determined by detergent fiber analysis. The sums of neutral sugars determined calorimetrically correlated closely with the values obtained by GLC analysis after Saeman's hydrolysis (2 hr with 72% (w/w) HzS04 at 20°C and 2 hr with 2N H2S04 at 100°C) of defatted samples. The GLC data were, however, consistently higher, especially those for hexoses; the difference was more pronounced with feces than with tested bran material. Confidence in the analysis was strengthened by the observation that the results of proximate and fiber analyses closely approached 100%.

Measuring lignin in human and rat faeces

“…We have previously observed nitrogen in lignin from faecal neutral detergent fibre (NDF), a fibre fraction obtained under conditions of moisture and heat (Marlett and Johnson 1985). Rasper et al (1981) have reported that artefact lignin was produced during rat faecal fibre analysis unless the samples were treated extensively with pepsin to remove protein. These 'lignins' must be generated either during gut transit or during analysis.…”