Validation of a size exclusion liquid chromatographic method for determination of methylcellulose and hydroxypropyl methylcellulose food gums as soluble dietary fiber in food and food product

A size exclusion liquid chromatographic method was developed for the determination of methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC) as dietary fiber in food. These modified cellulose food gums are used in a wide variety of foods and physiologically behave as dietary fibers but are not determined using existing analytical dietary fiber methods. This article reports a single laboratory validation of a new method based on AOAC 991.43, and uses a liquid chromatograph with a refractive index detector. This new method was validated for foods containing 0.2–27% of MC and HPMC employing AOAC’s Single Laboratory Validation protocol. Ten food samples of meat, bread, milk powder, potato and orange juice drink mix were studied. Precision of the new method, measured as total standard deviation (St), varied from 0.01 to 2 for foods containing 0.2–27% MC; and from 0.05 to 0.2 for foods containing 0.5–3.8% HPMC. Recovery varied from 76% to 85% for MC, and from 75% to 113% for HPMC. Use of a blank matrix proved successful in correcting for indigenous food fibers. The method demonstrated excellent linearity down to 0.03%. This provides the sensitivity required for food nutrition labeling purposes. These results show the method is suitable for determination of MC and HPMC in food and support further validation through a collaborative study.