Determination of carbohydrates in sugarcane bagasse pulp in different TCF bleaching sequences

Changes in the carbohydrate content of cellulosic fibers during pulping and bleaching processes is a very important factor for evaluating every individual stage in pulp processing. The carbohydrate contents of raw depithed bagasse, soda pulp and bleached pulp, in each stage of two TCF sequences (OQPQP and OQPoQP), were determined by methanolysis and acid hydrolysis, and subsequently by gas-chromatography. Results showed that the bagasse hemicellulosic carbohydrates, representing about 24% of chemical components, were mostly composed of xyloses, glucose and L-arabinose sugars. The pulping process had the greatest effect on the amount of chemical components and their ratio, as the portion of all carbohydrates was increased. Also, the pulping process and all bleaching stages increased the cellulosic glucose content, while the hemicellulosic carbohydrates did not present significant changes in pulping and oxygen delignification stages. However, there was a significant reduction of hemicellulosic carbohydrates, especially in 5-carbon sugars, in the bleaching stages.