Physicochemical and functional characteristics of cassava starch in Ugandan varieties and their progenies

Ephraim Nuwamanya¹, Yona Baguma²*, Naushad Emmambux³, John Taylor³ and Rubaihayo Patrick¹

¹Department of Crop Science, Makerere University Kampala, P. O. Box 7062, Kampala, Uganda.

²National Crops Resources Research Institute (NaCRRI), P. O. Box 7084, Kampala, Uganda.

³Department of Food Science, Faculty of Agriculture, University of Pretoria, South Africa.

*Corresponding author. Email: ybaguma@naro-ug.org,  bgmyn@yahoo.co.uk.

Accepted   25 November, 2009

   Abstract

Due to poor root quality traits in improved, disease resistant cassava (Manihot esculenta Crantz.)  varieties and hence low acceptability among farmers, a study was undertaken to improve these varieties by crossing them with disease susceptible, farmer preferred local landraces. Five improved varieties and four local landraces were used and hybridisations among them were made in a poly-cross nursery block.  Starch isolated from the nine cassava varieties and their F₁ progenies was analysed for physicochemical and functional properties. Significant differences were observed between varieties, progenies and within the F₁ progenies. The amylose content ranging between 19.0 - 25.0% was negatively correlated to swelling power and solubility but positively correlated to starch content. Average starch granule sizes ranged between 7.0 - 12.0 mm, though smaller granules ranged between 2 - 6.9 mm and large granules between 13 – 20 mm. Granules were mainly truncated in shape and similar across varieties and their progenies. Individual parents had peak viscosity, set back viscosity and viscosity at breakdown higher than the progenies suggesting inherent genetic and biochemical differences among parents used in the study. Variations were also observed in the parents and progenies for starch swelling power, solubility and starch content on dry basis. Starch associated molecules such as proteins and lipids did not vary significantly but dietary fibre significantly (P< 0.05) varied both in parents and F₁ families. Significant correlations (r > 0.45) were observed among starch properties including swelling power and breakdown viscosity. Based on these results, selections for lines with different starch quality and quantity properties can be made among the F1 families for future dietary and industrial uses.

Key words: Progenies, starch granules, viscosity, physicochemical properties.