Unlocking the potential of bean starch (Phaseolus vulgaris L.): How sequential dual modification by γ-radiation and dry heat enhances structural, thermal, and functional properties.

This study investigated the effects of dual modification (gamma radiation and dry heat treatment) on bean starch (Phaseolus vulgaris L.), analyzing structural, thermal, and functional changes. Continuous (CDHT) and repeated (RDHT) dry heat treatments (120 °C/3-9 h) were applied in combination with gamma radiation (10 kGy) in different sequences (γ-DHT and DHT-γ). The results showed that both treatments caused granule fissures and aggregation, with more pronounced effects in repeated cycles (RDHT). Gamma radiation slightly reduced crystallinity, while its combination with DHT increased thermal stability (with higher gelatinization temperatures T and T) and gelatinization enthalpy change (ΔH up to 19.4 J/g). Dual modification also significantly increased retrogradation tendency (up to 78.1 %), indicating a greater tendency for molecular reorganization. Fourier-transform infrared (FT-IR) spectroscopy analysis indicated that no new functional groups were formed after the modifications. One of the most significant findings was that samples treated with γ-DHT retained a higher resistant starch (RS) content after cooking (18.27 % vs. 3.10 % in the control), a valuable characteristic for developing low-glycemic-index foods. Regarding pasting properties, a significant reduction in viscosity was observed, especially in γ-DHT treatments, attributed to molecular degradation. The results demonstrate that the sequence of treatment application is relevant, with the γ-DHT approach being the most promising for starch modification.