title: Comparison of microwave oven and convection oven for acid hydrolysis of dietary fiber polysaccharides.
abstract: Hydrolysis of dietary fiber polysaccharides (DFP) is an integral part of any enzymatic-chemical method for dietary fiber analysis. Residues obtained after enzyme treatments of fiber-containing foods are usually suspended in 12 M sulfuric acid and kept at or slightly above ambient temperature for at least 1 h, and then the mixtures are diluted with deionized water to a final concentration of 1 M or 2 M acid, followed by heating at 100 degrees C in a water bath or convection oven for 1 or 2 h. Under these hydrolytic conditions, some degradation of the released monosaccharides generally takes place over the duration of hydrolysis. We investigated the feasibility of using microwave energy as a heat source to reduce time and minimize degradation. Preliminary tests were done on the well-characterized soy polysaccharide Fibrim. With a microwave digestion system equipped with temperature and pressure monitors and control lines, optimum settings of power (5%, 75%), time (up to 3 min and 30 s), temperature (35 degrees-55 degrees C), and pressure (45-65 psi) were determined for different foods depending on the residue weight and volume of acid. Results were comparable for microwave oven and convection oven hydrolysis of DFP from 5 foods with good correlations for neutral sugar values; r2 = 0.997 for arabinose, 0.925 for galactose, 0.981 for glucose, 0.969 for mannose, and 0.990 for xylose.
authors.affiliation: U.S. Department of Agriculture, Beltsville Human Nutrition Research Center, Food Composition Laboratory, MD 20705, USA.
authors.forename: B W
authors.initials: BW
authors.lastname: Li
mesh_terms: D001089:Arabinose / Q000032:analysis; D018481:Convection; D004043:Dietary Fiber / Q000032:analysis*; D005690:Galactose / Q000032:analysis; D005947:Glucose / Q000032:analysis; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008358:Mannose / Q000032:analysis; D008872:Microwaves; D011134:Polysaccharides / Q000737:chemistry*; D013025:Glycine max / Q000737:chemistry; D013464:Sulfuric Acids; D014574:Uronic Acids / Q000032:analysis; D014994:Xylose / Q000032:analysis
chemical_list: D004043:Dietary Fiber; D011134:Polysaccharides; D013464:Sulfuric Acids; D014574:Uronic Acids; D014994:Xylose; D001089:Arabinose; D005947:Glucose; C033158:sulfuric acid; D008358:Mannose; D005690:Galactose