Determination of Ferulic and p-Coumaric Acids in Wheat Straw and the Amounts Released by Mild Acid and Alkaline Peroxide Treatment

Abstract

Ferulic acid (FA) and p-coumaric acid (PCA) are two major phenolic acids in a wide variety of graminaceous plants. Particularly, FA has been implicated in cross-linking cell wall polymers. In the present paper, the variations in FA and PCA contents of wheat straw upon various treatments relevant to the process of producing paper-making fibers were investigated. Wheat straw contained 0.48% FA and 0.42% PCA on the basis of dry material. Among them, of the total FA, 56% was esterified only and 44% was etherified. In contrast, >80% of the PCA was esterified only. In general, the phenolic acids had a high tendency to dissolve in hot water or alkaline peroxide solution, as compared to lignin. Nevertheless, the two-step pulping process, a mild acid wash followed by alkaline peroxide bleaching, removed <40% of FA and <20% of PCA. The phenolic acids remaining attached to the lignin might have an effect on the properties of wheat straw fibers made according to this method. Keywords: Ferulic acid; p-coumaric acid; lignin; wheat straw; alkaline peroxide bleaching