Influcence of cooking procedures on structure and biochemical changes in sweet potato

Fresh sweet potato roots from a selected cultivar (VIII-18) were either boi led or steamed. with or without a precooking step. Significant structural a nd physicochemical changes occurred as a consequence. Whatever the cooking procedure, native starch granules were gelatinised and starch macromolecule s were totally reorganised, forming networks inside the cells. The structur e of the starch network and the pore sizes were dependent upon the method o f cooking and highly variable from one cell to another. Cell walls were les s damaged when roots were submitted to a precooking stage before cooking. H owever, cell walls were drastically damaged by steaming, even when roots we re precooked, giving rise to a soggy texture. Physical and biochemical anal ysis showed a dual behaviour: an increase in cell wall strength could be re lated to an increase in insoluble cell wall polysaccharides due to cooking, whereas a part of cell wall being solubilised in cooking water.