This method seeks to describe the preparation of samples for cell wall polysaccharides analysis in order to assess the amount of the different types of sugars contained in the cell walls of raw and boiled yam and plantain. The extraction of cell wall polysaccharides (CWP) involves several steps. Yam and plantain are rich in starch polysaccharides (>80% d.b.) in order to obtain reliable and measurable data on cell wall polysaccharides, starch removal is mandatory before cell wall analysis. This step has been particularly optimized. This SOP has been developed on commercial yam and green plantain, as they are particularly high in starch. It was then applied to various yam and banana samples at different ripening stages (fresh fruits, cold powders or freeze-dried). The preparation of CWP samples from amylaceous products requires 4 steps: (i) extraction of alcohol insoluble solids (AIS) to remove all the soluble sugars and polyphenols, (ii) starch removal in aqueous solution thanks to enzymatic reactions, (iii) quenching by 96% EtOH, followed by new extraction of destarched AIS, to remove the soluble sugars and polypeptides produced by the starch removal process, and finally (iv) starch assay to assess the efficiency of the starch removal process.