Comparative Structural and Functional Characterization of Underutilized Tropical Tuber Starches: Implications for Pharmaceutical Excipient Development

Abstract

The starches from tigernut ( Cyperus esculentus ), two varieties of water yam ( Dioscorea alata ) and trifoliate yam ( Dioscorea dumetorum ) were comparatively evaluated for their structural and functional properties and the implications for pharmaceutical excipient development. The extracted starches were characterized for yield, proximate composition, amylose concentration, hydration characteristics, pasting behavior, thermal properties, crystalline structure, granule shape, and short‐range molecular order. The starches were of high purity with low residual protein, fat, and ash concentrations. Amylose concentration was in the range of 25.25%–30.18%. Relative crystallinity was similar (28.0%–28.2%) despite different crystalline polymorphs. Water yam starches showed increased water absorption capacities and peak viscosities (483–513 RVU), while trifoliate yam starch had the highest pasting temperature (85.7°C), lowest breakdown viscosity (72 RVU), and reduced setback viscosity, indicating better thermal and shear stability. Differential scanning calorimetry showed onset gelatinization temperatures between 61.55°C and 80.95°C, indicating differences in starch crystalline organization. Tigernut starch had small, spherical granules with A‐type crystallinity, while water yam starches had larger granules with C‐type polymorphism. These results show that less‐used tropical tuber starches have different structural and physicochemical properties that could support their future use in pharmaceutical excipient development. However, more formulation and performance assessments are needed to prove their use in pharmaceutical dosage systems.