Determination of starch digestibility in white sweet potato after acid hydrolysis and heat-moisture treatment using terahertz spectroscopy

Acid hydrolysis and heat-moisture treatment (HMT) have been used to alter digestibility of starch in white sweet potato, providing health benefits. The potential of terahertz spectroscopy for rapid and non-destructive determination of starch digestibility in white sweet potato treated with acetic acid and citric acid, followed by HMT, was investigated. An in vitro starch digestibility assay was employed to measure the contents of rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS). The intensities of the peaks attributed to covalent vibrational modes at 9.0, 10.5, and 13.1 THz showed a strong correlation with RDS content (R² > 0.95). Moreover, the intensities of the peaks sensitive to non-covalent forces within and between double helices of starch, around 5.0 and 7.9 THz, were correlated with RS content (R² > 0.65). These results indicate, after acid hydrolysis and HMT, the starch digestibility of white sweet potato can be determined using THz peaks.