Dept. of Food Science and Technology, University of Karachi, 75270 Karachi, Pakistan.
Dept. of Food Science and Technology, University of Karachi, 75270 Karachi, Pakistan.
Int J Biol Macromol. 2020 Dec 1;164:3048-3054. doi: 10.1016/j.ijbiomac.2020.08.105. Epub 2020 Aug 14.
The aim of the study was to compare the properties of resistant starch (RS) 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 (ES) as compared to corn extrudate (EC) (64.90%), on 14th day of storage. The increase in RS correlates with the increase in percent crystallinity (%Xc), too. The (ES) 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/1151 cm and 1047 cm/1022 cm. 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 (ES) exhibited glycemic index equal to (EC) i.e.55.53 and 52.53, respectively; thereby making it a suitable substitute of corn starch.
本研究旨在比较玉米淀粉和高粱淀粉在挤压过程中形成抗性淀粉（RS）的性质。挤出物在 4°C 下储存 7 和 14 天，以允许分子重排，即回生。分析了挤出淀粉的酶消化率、长程（X 射线衍射，XRD）和短程（FTIR）分子有序性、热特性（DSC）和受温度影响的流变特性。与玉米挤出物（EC）相比，高粱挤出物（ES）在第 14 天储存时的 RS 含量最高（70.64%），而 RS 含量最高。RS 的增加与结晶度百分比（%Xc）的增加相关。（ES）在所有挤出物中报告的%Xc 最高，即 37.83。XRD 结果表明在 13°和 20°处出现了附加峰，反映了所有样品中 V 型图案的形成。傅里叶变换红外光谱（FTIR）也显示出 1047cm/1151cm 和 1047cm/1022cm 的比值增加。挤出淀粉表现出明显更高的热稳定性和更低的冷糊粘度。随着储存时间的增加，血糖指数显著（p≤0.05）降低。（ES）表现出的血糖指数与（EC）相等，分别为 55.53 和 52.53，因此它是玉米淀粉的合适替代品。
