Structural and functional characterization of RS III produced from gelatinized, enzyme-hydrolyzed and retrograded sweet potato starch

Abstract

The demand for the application of resistant starch as a functional ingredient is growing, thus, the analysis of its structural, thermal and digestibility properties can help food producers in optimizing industrial applications. The effect of autoclaving (120 °C/30 min)-debranching (2% pullulanase/50 °C) time (1 or 11 or 21 h) and retrogradation temperature (4 or 32 or 60 °C/24 h) on sweet potato starch fractions were studied. Further, the functional, pasting, thermal and structural properties of gelatinized, enzyme-hydrolyzed and retrograded (GEHRS) were also investigated. All the treated starches exhibited a dextrose equivalent value ranging between 3.70 and 5.30%. Debranching of starch at 50 °C for 21 h and retrogradation at 4 °C yielded 63% of RS. Results showed that most of the functional properties had been enhanced in GEHRS. GEHRS registered a lower pasting profile, higher gelatinization temperatures and displayed the B + V diffraction pattern with an increased crystallinity. The SEM of debranched starches showed rough plate-like surfaces with irregularly shaped structures. The study concludes that pullulanase debranching of sweet potato starch at 50 °C for 21 h and subsequent retrogradation at 4 °C produce a higher amount of resistant starch in sweet potato starch.