Blackcurrant stems: A novel non-tree fibre for the production of pulp and paper

Debarked stems of blackcurrant (Ribes nigrum L.; cv. Ben Alder) were hammer-milled and extracted with water (70°) and diethyl ether. The residue was subjected to alkaline extractions with increasing concentrations of aqueous NaOH and chlorite delignification. Analysis of the neutral sugar, lignin and uronic acid contents of the residues and extracts indicated that blackcurrant stem should be considered as a typical hardwood. The 0.1 M and 1.0M NaOH extracts provided both hemicellulose (H/C) A and a H/C B fraction, while the 4.5M NaOH extract only yielded the latter. The principal polysaccharides in all these fractions were glucuronoxylans. These were present at higher concentrations in each H/C B fraction than the corresponding H/C A fraction. Other polysaccharides present were arabinoglucuronoxylan, glucomannan, mannan and galactan. The extracted lignin contents were greatest in the H/C A fractions. The effects of chlorite delignification were largely confined to a reduction in the residual lignin content by c. 94%. This was confirmed by FT-IR spectroscopy. Four distinct cell types were found in blackcurrant stems ; tracheids, libriform fibres, vessel elements and ray parenchyma cells. These cell types are also present in a typical hardwood, although their dimensions were smaller. The results of the study suggest that blackcurrant stem fibres have the potential to be used along with existing wood-based fibres in the production of pulp for paper manufacture.
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