Thermal and structural characterisation of resistant starch from Andean roots cultivated in Colombia

Abstract

Resistant starch (RS) is a type of dietary fibre with recognised health benefits. This study aimed to obtain and characterise RS from Andean roots, resources that have a low ecological footprint and contribute to agroecosystem resilience under climate change, while remaining rooted in traditional cultural practices. Starch extracted from achira (Canna edulis Ker), ibia (Oxalis tuberosa Molina) and batata (Ipomoea batatas Lam) was subjected to enzymatic debranching followed by autoclave-cooling (AC) cycles according to a completely randomised 3 × 3 × 2 factorial design. The highest RS percentages (p ≤ 0.05) were obtained with two or three AC cycles of 90 or 120 min at 121 °C for I. batatas (46.23% RS), with two AC cycles of 120 min at 130 °C for C. edulis (48.02% RS) and with three AC cycles of 90 min at 130 °C for O. tuberosa (45.37% RS). Total dietary fibre (%TDF) in RS increased by 10.88% for I. batatas, 12.88% for C. edulis and 10.21% for O. tuberosa compared with their native starches (NSs). Thermogravimetric analysis showed greater thermal stability of RS against degradation than NS. Differential scanning calorimetry revealed that RS exhibited lower gelatinisation temperatures (Tg) and enthalpy (ΔHg) and a broader gelatinisation range (ΔTg) than NS, due to the formation of retrograded structures with heterogeneous and less hydrated crystalline regions. X-ray diffraction patterns showed a C-type crystallographic pattern for C. edulis RS and mixed B- and V-type patterns for RS from I. batatas and O. tuberosa. Infrared spectra (FTIR-ATR) confirmed a higher degree of retrogradation and distinct crystalline organisation in RS compared with NS. These properties highlight the potential of RS from Andean roots as functional ingredients with prebiotic benefits.