A comparison between the properties of seed,starch, flour and protein separated from chemically hardened and normal kidney beans

The physicochemical, functional and thermal properties of starch, flour and protein isolates obtained from chemically hardened kidney beans were evaluated. A rapid chemical hardening procedure (soaking in acetate buffer, pH = 4.0, 37 °C, 6 h) was used to produce hardened kidney beans. Chemical hardening altered physicochemical, cooking, hydrating and textural properties of beans to a significant level (P < 0.05). Soaked and cooked chemically hardened beans had a higher value for different textural parameters than their normal counterparts. Chemical hardening increased cooking time (from 49 to 123 min) of beans and decreased swelling power and solubility of starch. The turbidity value of gelatinized starch suspensions from chemically hardened beans was significantly lower than that from normal beans. Chemical hardening of beans caused significant increase in transition temperatures (T_o, T_p, T_c) and enthalpy of gelatinization (ΔH_gel) of both starch and flour. Chemically hardened bean starch showed significantly higher pasting temperature (94.9 °C) as compared to normal bean starch (83.2 °C). Flour and protein isolate from chemically hardened beans showed significantly lower water absorption, oil absorption, foaming capacity and gelling ability than those from normal beans. The onset temperature (T_m), peak denaturation temperature (T_d) and heat of transition or enthalpy (ΔH) of protein isolate from hardened and normal beans did not differ significantly. Copyright © 2007 Society of Chemical Industry