Fortification of dietary fiber in cassava pulp by conversion of the remaining starch to resistant starch

A novel high-fiber product enriched with resistant starch type 3 (RS3) was successfully prepared from cassava pulp (CP). The remaining starch in CP underwent debranching and retrogradation processes to convert it to RS3. Pullulanase was used to debranch the starch in CP at 55°C for 24 h, followed by incubation at 4°C for various retrogradation time intervals: 0, 6, 12, 24, 48, 72, 96, and 120 h. Retrogradation of the debranched starch in CP for 24 h resulted in a significant formation of RS3 (11.8%) with heat stability. Additionally, the total dietary fiber content of the obtained product increased from 47.4% to 59.4%. Structural analysis revealed the presence of small irregularly shaped and sponge-like particles of retrograded, debranched starch on the fiber matrix surface. The X-ray diffraction pattern of the CP revealed the presence of cassava starch (A-type) and cellulose (type I) crystals. After debranching and retrogradation, the crystalline structure transitioned to the B-type. The novel products showed higher lightness and whiteness index compared to CP. The gel of cooked products had a firm texture and a homogenous appearance. The functional properties of the obtained product demonstrated significant differences compared to CP. It exhibited enhanced water-holding capacity (10.2 g/g), oil-holding capacity (6.3 g/g), and swelling capacity (17.7 mL/g). Moreover, the product had a lower bulk density (0.13 g/mL) than the original CP. This innovative approach enhances CP's nutritional and functional qualities, offering potential for healthier, more functional food products.