Cereal Chem 66:289-295   |  VIEW ARTICLE

Isolation and Characterization of Lignin from Hard Red Spring Wheat Bran.

P. B. Schwarz, V. L. Youngs, and D. R. Shelton. Copyright 1989 by the American Association of Cereal Chemists, Inc. 

Dioxane-extractable lignin (DEL) preparations were isolated from hard red spring (HRS) wheat bran (bran DEL) and HRS wheat outer pericarp tissue (pericarp DEL). Alkali lignin was prepared from the bran (bran AL). Prior to lignin extraction, the bran and outer pericarp tissues were treated to remove nonlignin materials. Treatments included pin milling, air classification, and enzymatic digestion. Bran DEL contained 0.86% nitrogen and 18% carbohydrate, whereas the bran AL and pericarp DEL contained, respectively, 1.95 and 1.06% associated nitrogen and 0.9 and 2.2% associated carbohydrate. Esterified hydroxycinnamic acids were detected in the bran DEL preparation. These consisted largely of trans-ferulic acid with lesser amounts of trans-p-coumaric acid. Ultraviolet spectroscopy indicated the absence of these compounds in the bran AL and pericarp DEL isolates. Bran DEL was characterized by nitrobenzene oxidation. The molecular weight distributions of the bran DEL and AL isolates were determined by gel permeation chromatography. The bran AL isolate had a high average molecular weight, whereas that of the bran DEL isolate was quite low. All lignin preparations were obtained only in low yields, perhaps representing less than 5% of the total tissue lignin.