Alterations in Cell Wall Constituents of Yams Dioscorea dumetorum and D. rotundata with Maturation and Storage Conditions. Relation with Post-Harvest Hardening of D. dumetorum Yam Tubers

Hot water-insoluble cell wall polysaccharides of immature and mature Dioscorea dunietomin and D. rotundata yam tubers have been characterized in enzymatically destarched flours and were mainly constituted of cellulose followed by hemicellulosic polymers of xylose, galactose, mannose and arabinose. Immature tubers of both species contained a higher proportion of cell wall carbohydrates than mature ones essentially because of their low starch content. Storage of mature tubers of both species induced an increase of cell wall polysaccharides content particularly for D. dumetorum. The strong hardening of D. duinetoiuin yam during storage was characterized by the deposition of a xylose-containing polymer and of additional cellulose and by the lignification of the tubers.