Structural, functional and digestibility characteristics of sorghum and corn starch extrudates (RS3) as affected by cold storage time

• Published in: International journal of biological macromolecules 2020-12, Vol.164, p.3048-3054
• Main Authors: Shaikh, Faiza, Ali, Tahira Mohsin, Mustafa, Ghulam, Hasnain, Abid
• Format: Article
• Language: English
• Subjects: Carbohydrate Sequence; Extrusion; Resistant starch; Rheology; Sorghum - chemistry; Spectroscopy, Fourier Transform Infrared; Starch; Starch - chemistry; Thermodynamics; X-Ray Diffraction; Zea mays - chemistry
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2020.08.105

The aim of the study was to compare the properties of resistant starch (RS3) formed during extrusion of corn and sorghum starches. The extrudates were stored for 7 and 14 days at 4 °C to allow for molecular rearrangement i.e. retrogradation. The extruded starches were analyzed for enzymatic digestibility, long range (X-ray diffraction, XRD) and short range (FTIR) molecular order, thermal characteristics (DSC) and rheological properties as affected by temperature. The highest RS (70.64%) was obtained for sorghum extrudate (ES14) as compared to corn extrudate (EC14) (64.90%), on 14th day of storage. The increase in RS correlates with the increase in percent crystallinity (%Xc), too. The (ES14) reported the highest %Xc among all extrudates i.e.37.83. The XRD results showed an additional peak at 13° and 20°, reflecting the formation of V-type pattern in all samples. The FTIR spectroscopy also exhibited increase in the ratio of 1047 cm−1/1151 cm−1 and 1047 cm−1/1022 cm−1. The extruded starch showed significantly higher thermal stability and lower cold paste viscosity. The significant (p ≤ 0.05) decrease in the glycemic index was obtained as the storage time increased. The (ES14) exhibited glycemic index equal to (EC14) i.e.55.53 and 52.53, respectively; thereby making it a suitable substitute of corn starch. •Sorghum starch is a sustainable alternative to corn starch in future.•The starch was extruded and stored at 4 °C to produce RS3 i.e. retrograded starch.•The sorghum extrude (after 14 days' storage) produced highest RS fraction (70.6%).•The highest percent crystallinity was observed for (ES14) starch.•The DSC results also confirmed the higher melting enthalpy for ES14.