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. 2019 Aug 15;135:314-327. doi: 10.1016/j.ijbiomac.2019.05.115. Epub 2019 May 21.
The present study isolated starch from corn and sorghum grains through wet milling procedure. Sorghum starch is considered an alternative to corn starch in future, due to similar functional properties. However, agronomically sorghum is a cheap input cost crop compared to sorghum and can grow in drought hit areas. Lactic acid and citric acid modifications along with heat-moisture treatments were performed on both sorghum and corn grains followed by their comparison in terms of functional, textural, thermal, pasting and digestibility characteristics. For both corn and sorghum starches, the resistant starch increased after chemical modifications. The RS content of acid and acid-heat moisture treated starches were in the range of 77.9-90%, significantly higher than those of native starches (64.6-68.8%). The modifications increased the gelatinization temperature, decreased the peak and cold paste viscosity of starches. Chewiness significantly reduced after lactic and citric acid treatment along with heat-moisture treatments. The crystallinity to amorphous ratio measured through Fourier Transform infrared reduced after all chemical treatments. Percent light transmittance was further reduced after heat-moisture treatments, however the effect on corn starch was more pronounced i.e. it declined from 16.5 to 5.2%. The acid-heat moisture treatments had considerably lowered the glycemic index of starch. The GI reduced from 74 to 49.7 and 60 to 48.5 when treated with acid in the presence of heat and moisture. Thus, these starches could be used in production of low-calorie foods.
本研究通过湿法碾磨工艺从玉米和高粱谷物中分离出淀粉。由于具有相似的功能特性，高粱淀粉被认为是未来玉米淀粉的替代品。然而，与高粱相比，高粱作为一种廉价的农业投入作物，可在遭受旱灾的地区生长。对高粱和玉米进行了乳酸和柠檬酸改性以及湿热处理，然后比较了它们在功能、质构、热学、糊化和消化特性方面的差异。对于玉米和高粱淀粉，化学改性后抗性淀粉增加。酸和酸-热-湿处理淀粉的 RS 含量在 77.9-90%之间，显著高于原淀粉（64.6-68.8%）。改性提高了淀粉的胶化温度，降低了峰值和冷糊粘度。经过乳酸和柠檬酸处理以及湿热处理后，咀嚼性显著降低。通过傅里叶变换红外光谱测量的结晶度与无定形比率降低。经湿热处理后透光率进一步降低，但对玉米淀粉的影响更为明显，透光率从 16.5%降至 5.2%。酸-热-湿处理大大降低了淀粉的血糖指数。当在热和水分存在下用酸处理时，GI 从 74 降低到 49.7 和 60 降低到 48.5。因此，这些淀粉可用于生产低卡路里食品。
