Abstract: The starch blocking stability of speckled kidney beans (Phaseolus vulgaris) alpha-amylase inhibitor (α-AI1) for application as a nutraceutical additive against diabetes and obesity was assessed. The inhibitor was purified to 0.09% w/w of seed flour using pH fractionation, alcohol precipitation (75%), DEAE-Sepharose CL-6B and Sephacryl S-200 chromatography. The interactive effect of pH (A), temperature (B) and time (C) on residual inhibitory activity was modeled using Response surface methodology with the Box-Behnken design. Intrinsic fluorescence and ANS-assisted surface hydrophobicity indicated activity loss is accompanied with tertiary structural unfolding. Chaotrophic salts at high (1.0 M) and kosmotrophic salts at low (0.1-0.01 M) concentration stabilized the inhibitor in the order CH3COO– > Cl–>Br– >I– > SCN– and vice-versa, respectively.