MODIFIKASI TEPUNG UMBI KIMPUL: PENINGKATAN KADAR PATI RESISTEN DAN KARAKTERISASI SIFAT FUNGSIONAL DENGAN FERMENTASI SERTA PEMANASAN BERTEKANAN-PENDINGINAN

Kimpul tuber flour predominantly contains rapidly digestible starch, which can elevate the glycemic index. To convert a portion of this starch into a digestion-resistant fraction, flour modification is required. Resistant starch bypasses degradation in the small intestine and functions as dietary fiber and a prebiotic.Therefore, this study investigated the potential of combining fermentation with pressurized heating–cooling treatments to enhance resistant starch content and improve the functional properties of kimpul tuber flour. Surface morphology and granule structure changes were examined by Scanning Electron Microscopy (SEM) at 500,000× magnification to visualize three-dimensional topography. The research unfolded in two stages. In Stage I, interactions among two lactic acid bacteria strains (L. bulgaricus and L. plantarum) and a commercial bacterial mix (Bimo-CF) were evaluated for their effects on resistant starch content and functional properties of the modified flour. Stage II assessed the efficacy of combining optimal fermentation with pressurized heating–cooling cycles to further increase resistant starch and characterize resulting chemical, functional, and particle morphology changes. Stage I results indicated that fermenting modified kimpul flour with L. plantarum for 36 hours was the best treatment, yielding 24.22% resistant starch, 36.9% swelling power, and a 6.10% water solubility index. In Stage II, applying three pressurized heating–cooling cycles (15 minutes each) after fermentation increased resistant starch to 26.66% (a 2.44% improvement over Stage I), with 33.52% swelling power, a 3.83% water solubility index, 13.94% moisture content, 1.65% ash content, and a lightness (L) value of 84.74. SEM analysis of the pressurized heating–cooling–treated flour revealed predominantly spherical to sub-spherical granules with visible damage to the starch structure.