Lignin studies I. Investigations concerning lignin determination

Authors

• Maija-Liisa Salo Department of Animal Nutrition and Husbandry, University of Helsinki

DOI: https://doi.org/10.23986/afsci.71423

Abstract

In this investigation a sulphuric acid method for the determination of lignin is presented and the influence of various details critically studied. The samples ground to pass through a 60 mesh (0.25 mm.) screen gave 0—5 % smaller results than those ground through an 1 mm. screen. Locating the extraction with ethanol-benzene before or after the prehydrolysis had no significant influence on the lignin values. The refluxing with water before the acid prehydrolysis lowered the lignin values (N-free) to some extent. The pepsin pretreatment lowered them still further. The nitrogen content of the part of crude lignin which was digested by pepsin was 9—13 %. On the nitrogen content of crude lignin obtained from faeces the use of pepsin had no influence. The hydrolysis procedure with 72 per cent sulphuric acid did not appear to be conventional as to the extension of the hydrolysis above the time needed, the effeciency of the stirring of the mixture or the stability of the temperature. The refluxing of the dilution after 72 per cent acid treatment was not necessary if the acid prehydrolysis was sufficiently effective. The lignin values obtained by different acid methods correspond to each other provided that certain fundamental principles are followed.