Functional properties of starches from tropical roots and tubers : Starch behaviour under different agro-industrial stress conditions

This study was undertaken to evaluate the possibility of using starches from non-conventional sources as alternative solutions when specific functional properties are not provided by conventional starches. Twenty two non-cereal starches, 17 of which were from roots and tubers from South America, were evaluated and compared to common starches from cereals, potato and cassava. Variability among clones was evaluated using germplasm (cassava, sweetpotato, yarn, taro, and canna) frorn Latin America, Africa and the Pacific region. Several functional properties, mostly sought by industrial users, were determined: hot paste viscosity, clarity of the gel, resistance to acidic medium (pH 2.4) and to sterilisation (121°C for 2 hours) and stability of paste at -20°C. Several starches presented promising results, like starch from Canna indica that has very high hot paste viscosity and is resistant to sterilisation and acidic condition and -starch from Arracacia xanthorrhiza that gave clear paste with low syneresis during freezing storage conditions. The functional properties were related to starch physico-chemical characteristics. Amylose content was strongly correlated to resistance to acidic medium and degree of syneresis. On the other hand, hot paste viscosity was mainly related to starch granule size: the largest the granule, the higher the viscosity. In addition, gel clarity appeared to be positively correlated to hot paste viscosity, reflecting the predominance of starch swelling and disintegration during cooking on gel clarity.