Characterization and proprieties of cellulose isolated from the Crambe abyssinica hull
Introduction
Crambe abyssinica (crucifer family) is an annual herbaceous plant found, in the wild form, in the Abyssinian foothills and the North African plain. Studies of C. abyssinica seed as a new source of oil for food (i.e. confectionery and margarine) and industrial uses (i.e. mineral and mould lubricants in the manufacture of greases and in steel casting) have been in progress since the early 1960s (Grashchienkov, 1959, Anon, 1966, Cornelius and Simmons, 1966).
Experimental cultivation has resulted in a good quality hull-free seed containing 46% oil and 27% protein, the latter being present in the meal residue after oil extraction. The amino acid composition of the protein in the meal residue indicates good nutritional quality, thus the meal has potential as a feed for animals (Mustakas et al., 1965). However the presence of 8–10% thioglucosides and other antigrowth factors means there are palatability problems (Van Etten et al., 1965, Kirk et al., 1966), hence the need for chemical or enzymatic modification of the thioglucosides. However the trend nowadays is towards the extraction of some thioglucosides (i.e. epi-progoitrin glucosinolate) from the defatted meal for the production of enatiomerically pure fine chemicals (Aliano et al., 1977).
The experimental seed contained about 24% hull, a proportion that is a preliminary positive guide to the sample quality. In fact some samples grown or harvested under non-optimal conditions contained an abnormally large proportion of hull due to the pods being only partly filled or containing incompletely developed seeds (Cornelius and Simmons, 1966). Nevertheless it must be remembered that the overall economics of Crambe abyssinica processing are considerably influenced by the exploitation of the by-products, the hull in primis.
The objective of this work was to study the characteristics of the hull cellulose component for its feasible exploitation as a parent polymer of chemical derivatives.
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Materials and treatments
C. abyssinica hull was supplied by Enesad (France) within the framework of a European Concerted Action (AIR3 CT 94-2480) and was used as received. The bleached softwood kraft pulp (BKP) was a commercial sample supplied by Fincell (Finland). All solvents were commercial products and were used without any purification.
Results and discussion
The first aim of this work was the characterization of the untreated hull and the choice of alternative processes for cellulose isolation, based upon environmental impact reduction. The STEXT was also chosen for its high capacity to fractionate the starting material in the three major components, and OST for its high power of element separation.
By SEM analysis the C. abyssinica hull, as such, was found to consist mainly of the seed hull fragment (Fig. 1a) covered on the outside by a cuticle on
Conclusions
Exploitation of all the components of the annual C. abyssinica plant is the most important condition for both the successful commercialisation of the crop and a significant reduction in oil cost and ,hence, of all its derivatives. Both STEXT and OST are useful in isolating the cellulose component from the whole hull, without inducing any significant molecular degradation. C. abyssinica cellulose results in a polymer suitable for the preparation of chemical derivatives.
Acknowledgements
This work was supported by the European Community (Concerted Action: AIR CT-94-2480). Special thanks are extended to V. Richter and S. Orlandini for their experimental work.
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