Chapter 3 - Extractives

Abstract

The extractives are a heterogeneous group of substances, which can be extracted from wood or straw using solvents like acetone or dichloromethane. The main extractives are resin acids, triglycerides, steryl esters, fatty acids, sterols, neutral compounds, such as fatty alcohols, sterols, and a variety of phenolic compounds. The chemical composition is dependent on the factors that influence the wood or nonwood species, such as straw, growing age, and environmental conditions. Extractives are a minor component, often constituting less than 2% of the total dry matter; they make a major contribution to the characteristics of wood or nonwood species. These extractives are low-molecular-weight compounds, and the different classes of extractives have different chemical behaviors. Among the residues, wheat, barley, rye, and rice straws are the most economically important raw materials and are used extensively for pulp and paper production in developing countries, particularly Algeria, Argentina, China, and India. In these countries, corrugating medium, board, and packaging paper are produced from high-yield unbleached straw pulps, whereas bleached straw pulps are used as a major furnish for fine-quality writing, printing, and other paper grades.