A method for determination of soluble dietary fiber in methylcellulose and hydroxypropyl methylcellulose food gums

A size-exclusion chromatographic approach is proposed as a modification to the currently practiced AOAC International methods, to provide reliable means for the determination of methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC) food gums as soluble dietary fiber (SDF). The official enzymic/gravimetric AOAC methods, including the most common method 991.43, do not reflect the SDF status of MC and HPMC, and possibly many other water-soluble cellulosics gums that may either gel or precipitate at high temperatures in 100% aqueous solutions, or may be soluble in approximately 71% ethanol. As referenced within this paper, all of these gums exhibit the characteristics of SDFs, from both the chemical and physiological standpoint. The enzymic digestion principle of the existing AOAC methods is left unchanged in general, with only very minor adjustments introduced. The SDF recovery determined by the modified method is 77% for MC and 90% for HPMC in 0.1% (wt/wt) aqueous solution and 93% and 99%, respectively, in a pound cake food matrix. The method has been adopted First Action by AOAC as method 2006.08.