The reactivity of lignin carbohydrate complex (LCC) during manufacture of dissolving sulfite pulp from softwood

•Pine heartwood contained covalent bonds between lignin and hemicellulose of phenyl glycosides, γ–esters and α-ethers types.•During sulfite cooking the α-ethers types linkages were absent in the pulp samples.•LCC bonds between lignin and wood polysaccharides might be a bottleneck for efficient lignin removal in sulfite pulping.