PHYSICOCHEMICAL AND FUNCTIONAL PROPERTIES OF RED KIDNEY BEAN STARCH AND CASSAVA STARCH- A COMPARATIVE STUDY

ABSTRACT Starch remains one of the most significant biopolymers in food and industrial applications, with functional and physicochemical properties that vary greatly depending on botanical origin. This study comparatively investigated the physicochemical and functional properties of starches extracted from red kidney bean (Phaseolus vulgaris) and cassava (Manihot esculenta) to evaluate their potential utilization in food and non-food systems. Starches were isolated using standard wet extraction methods and analyzed for granule morphology, proximate composition, pasting behavior, gelatinization characteristics, and functional properties. Results revealed notable differences between the two starches. Red kidney bean starch exhibited a higher amylose content (45.40%) compared to cassava starch (20.20%), reflecting a greater capacity for gel formation and retrogradation. Cassava starch demonstrated superior dispersibility (90%) and moderate bulk density (0.720 g/mL), while red kidney bean starch showed lower dispersibility (85%) and a slightly higher bulk density (0.800 g/mL), indicating tighter granule packing but slower hydration. Pasting analysis highlighted a high peak viscosity in cassava starch (499.25 RVU), signifying excellent swelling and thickening potential, whereas red kidney bean starch recorded a lower peak viscosity (187.08 RVU) but higher setback viscosity (228.83 RVU), indicative of strong gel stability and a greater tendency toward retrogradation. Gelatinization behavior further distinguished the starches: cassava starch exhibited a moderate onset temperature (To = 81.30°C) and enthalpy change (ΔH = 12.10 J/g), while red kidney bean starch showed a significantly higher peak temperature (Tp = 116.30°C) and enthalpy (ΔH = 15.40 J/g), suggesting a more ordered crystalline structure and greater thermal stability. Proximate analysis confirmed the purity of both starches, with low lipid (0.10%) and protein content (cassava: 0.10%, red kidney bean: 0.03%), although red kidney bean starch contained slightly higher ash levels (0.30%). Morphological examination revealed that cassava starch granules were predominantly smooth and rounded, whereas red kidney bean starch granules were larger, compact, and irregular, influencing hydration and functional behavior. Collectively, the findings demonstrate that cassava starch excels in applications requiring rapid solubilization, paste clarity, and smooth texture, making it ideal for instant foods and sauces. Conversely, red kidney bean starch offers superior gel strength, thermal stability, and structural integrity, suggesting its potential for biodegradable films, resistant starch production, and pharmaceutical delivery systems. This comparative evaluation underscores the importance of diversifying starch sources to reduce overreliance on conventional crops while unlocking the industrial potential of underutilized legumes. Future work should focus on starch modification and composite formulations to mitigate the retrogradation tendencies of red kidney bean starch and optimize functional performance for specific applications. Keywords: Gelatinization, solubilization, proximate, dispersibility, morphology, retrogradation.