Effects of Acetylation on the Micromeritics of Yam (Dioscorea sp.) Starch Powder for Pharmaceutical Application
Alexia C. Harvey , Amusa S. Adebayo, Andrew O. Wheatley, Helen N. Asemota , Cliff K. Riley
1 Department of Basic Medical Sciences (Biochemistry), University of the West Indies, Mona Campus, Kingston 7, Jamaica.
2 Department of Biopharmaceutical Sciences, College of Pharmacy, Roosevelt University, Schaumburg, IL 60192
3 College of Health Sciences, University of Technology, Jamaica.
Corresponding Author: Amusa S. Adebayo
Email: aadebayo02@roosevelt.edu, Phone: 847-330-4548
ABSTRACT
Background: Starch constituents contributes to its intrinsic and binding properties. Native starch is insoluble in cold water and tends to undergo uncontrolled viscosity (pasting) on application of heat. These inherent weaknesses of native starch powders have been modified through thermal and chemical processes such as acetylation, acylation, carboxymethylation, oxidation and pregelatinization
Objectives: Effect of acetylation on micromeritics of starch from five yam varieties grown in Jamaica was investigated.
Methods: Native starch pre-treated with pyridine was reacted with acetic anhydride and acetylation process was monitored with Fourier Transformed Infrared Spectroscopy (FTIR) and by volumetric titration of the hydrolyzed starch acetate. Particle size and size distribution were determined microscopically and the mean diameter (dp) was treated to the Edmundson’s equation to obtain various derived size parameters.
Results: Yield of starch acetates ranged from 93.18 to 113.96% of different native starch varieties. Presence of a distinct peak in the ester range (1750-1735 cm-1) indicates acetylation and the degree of substitution was between 0.15±0.01 and 0.33±0.03. Starches from different yam varieties differ significantly (p<0.05) in specific surface area, particle mass, density, together with particle shape. These parameters could be used to distinguish starch acetates of different botanic sources. Correlation of degree of substitution with the amylose content and the specific surface area suggests that the amylose content contributed more significantly to the degree of the substitution than the effective surface area of the starch.
Conclusion: Acetylation resulted in significant changes of the micromeritics of varieties of native yam (Dioscorea sp.) starch powders and may impact formulation compressibility, fluidity, mixing and homogeneity.
Key words: acetylation, yam starch varieties, amylose content, micromeritics.