African Journal of Biotechnology Vol. 5 (17), pp. 1528-1536, 4 September 2006   

ISSN 1684–5315 © 2006 Academic Journals        

Full Length Research Paper

Isolation and Characterization of Starches from eight Dioscorea alata cultivars grown in Jamaica

Riley, C. K. ¹*, Wheatley, A. O.^1,2 and Asemota, H. N.^1,2

¹Biotechnology Centre and ²Department of Basic Medical Sciences (Biochemistry), University of the West Indies, Mona Campus, Kingston 7, Jamaica, W.I.

*Corresponding authors E-mail: cliff.riley@uwimona.edu.jm  Tel: (876) 9771828. Fax: (876) 9773331. 21 23

Accepted 14 July, 2006

Starches from eight Dioscorea alata cultivars grown in Jamaica were isolated and characterized. The starches were found to possess the open hydrated hexagonal crystalline pattern (type-B) with apparent amylose content ranging from 20.117 ± 0.017 gKg^-1 for Darknight yam to 23.001 ± 0.058 gKg^-1 for Barbados. The starch granules were found to display an asymmetric “Maltese” cross upon exposure to polarized light with projected mean granule diameters ranging from 22.89 µm to 28.01 µm. The starch granules were predominantly ellipsoidal in shape with only Renta yam and Barbados yam displaying triangular shaped granules. The swelling power of the starches were found to increase with temperature, with Moonshine (895.551 ± 1.051%) having the highest swelling power and Renta yam (757.401 ± 6.101%) the lowest at 95°C. Variations were also observed in the solubility, phosphorous content, crude fat content and gelatinization temperatures of the different yam starches. The properties of the different Dioscorea alata starches may prove useful in nutritional applications.

Key words: Dioscorea alata, yam, starch, crystallinity, amylase.