Extraction and fractionation of insoluble fiber from five fiber sources

Commercially processed wheat bran (WB), rice bran (RB), oat fiber (OF), tomato fiber (TF), and apple fiber (AF) were analyzed for proximate composition, soluble fiber (SF), insoluble fiber (IF) and total dietary fiber (TDF). IF was further fractionated into four fractions: cellulose, hemicellulose A and B, and lignin. Protein, IF, and TDF values were significantly different among the samples. Protein content ranged from 4.6% in OF to 24.9% in TF. SF values ranged from 1.5% in OF to 13.9% in AF. IF values varied from 46.7% in RB to 73.6% in OF. TDF ranged from 51.4% in RB to 75.1% in OF. Hemicellulose A to B ratio was high in all the samples except rice bran. WB had the highest total hemicellulose (44.0% of TDF) content followed by AF (38.4%), OF (38.3%), TF (36.5%), and RB (31.6%). Cellulose was 32.2, 26.6, 24.4, 20.8, and 19.7% of TDF in WB, OF, RB, AF, and TF, respectively. Lignin levels ranged from 5.2% in WB to 21.4% in OF.