Thermochemical modification of unripe plantain flour with fumaric acid: structure and functionality

BACKGROUND: Unripe plantain flour is naturally rich in resistant starch and of interest for developing foods with a reduced glycemic response but exhibits limited processing stability. Thermochemical modification using organic acids represents a promising strategy to alter starch structure, improve functional properties and stabilize resistant starch fractions. This study evaluated the techno-functional, physicochemical, structural, and digestibility properties of unripe plantain flour treated with fumaric acid. RESULTS: The treatment induced dual structural modifications, as evidenced by Fourier transform infrared spectroscopy and X-ray diffraction analyses, involving partial hydrolysis of glycosidic bonds and esterification of starch hydroxyl groups. These molecular changes led to a marked reduction in peak viscosity (approximately 90% compared to the native flour) and swelling power, as well as to a substantial increase in resistant starch content, reaching 86.74%. The modified flour also exhibited increased water solubility, reduced water-holding capacity and increased yellow coloration. CONCLUSION: Overall, thermochemical modification with fumaric acid effectively altered the structural and functional properties of unripe plantain flour. This treatment resulted in an ingredient with greater rheological stability and a higher resistant starch content than its native counterpart. Technologically, the modified flour exhibited a notable reduction in retrogradation-induced syneresis and gelation capacity, at the same time as retaining its oil absorption capacity. These characteristics support its potential application in food formulations requiring low viscosity (reduced thickening capacity) and a mitigated glycemic impact. Finally, it is recommended to optimize processing conditions to mitigate browning and adapt its functionality to specific food matrices.