4. Conclusion
The morphologies of the cells from the skin of Opuntia ficus indica, before and after disencrustation and homogenisation steps, were followed by optical and transmission electron microscopy. The microfibrillated cellulose, obtained after mechanical disintegration, contained collenchyma and parenchyma cells which were shown to be very stable gels in water. These cellulose microfibrils presented great similarities, in terms of composition and morphology, to those extracted from primary walls (particularly microfibrils made of parenchyma cells such as sugar beet pulp). These observations help to explain similarities in the rheological properties, as well. Thus, as stated in the different patents, MFCs from skins of OFI should find the same range of applications as those from other sources, such as sugar beet pulp, wood pulp and bacterial cellulose, all of which are used for their thickening, suspending, binding and coating properties. A noteworthy fact is that prickly pear fruits have better nutritional properties than have sugar beet roots. Finally, we note that OFI plants have minimal soil and water requirements and therefore are an interesting alternative for the agricultural economy of arid and semi-arid regions.