|Davis, Paul - FD&AG DIV, UC DAVIS|
|Daggy, Bruce - GLAXOSMITHKLINE|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 1, 2002
Publication Date: November 15, 2002
Citation: Yokoyama, W.H., Knuckles, B.E., Davis, P.A., Daggy, B.P. 2002. Stability of Ingested Methycellulose in the Rat Determined by Polymer Molar Mass Measurements by Light Scattering. Journal of Agricultural and Food Chemistry. 50:7726-7730. Interpretive Summary: Methylcellulose is used in foods, cosmetics and pharmaceuticals to add viscosity or thickness to liquids. It is a form of soluble fiber that can improve some digestive processes. It is not easily determined in foods because of its high solubility. We show that it can be determined efficiently using size exclusion chromatography (SEC) and instruments that characterize polymer size. We show that about one in ten polymer molecules are degraded by bacterial enzymes in the colon of rats. Previous studies had shown that methylcellulose is not absorbed. Some studies indicated rapid breakdown by fecal bacteria. The study shows it relative inertness in the digestive system of rats.
Technical Abstract: Methylcellulose (MC) is ingested by humans in food and pharmaceutical formulations. The functional properties of MC like those of other linear polymers depends primarily on polymer length or molar mass for largely linear polymers. Although many studies in animals and humans have shown complete excretion of MC in vitro human fecal fermentation studies indicate that MC can be degraded and presumable lose some of its functionality. In this study, MC polymer distribution in the feces from rats fed a diet containing 8% methylcellulose were compared to the fed MC. The water soluble polymers in the feces were separated by a size exclusion chromatography (SEC) and the polymer distributions determined by multiple angle laser light scattering (MALLS). Detection of the fluorescent MC-calcofluor complex was used to confirm the identity of the eluting MC peak. All dietary MC was recovered in the feces. There is a small shift (P<0.06) in the weight-averaged molecular weight of polymer distribution of MC extracted from the feces to 2.71+/-0.15x10E5 g/mol from 3.15+/-0.02x10E5 g/mol in the standard. There is also an increase in the polydispersity from 1/5 in the standard to 1/8 in the fecal extract. The distribution of the substituted methoxylated glucose monomers by gas chromatography also confirms the stability of MC fed to rats. The amount of actual hydrolysis is estimated to be about 0.1 per molecule. MC is not easily determined by standard dietary fiber methods and SEC with MALLS and/or fluorescence may be a useful alternative.