Effects of Ultrasonic Assisted Autoclave Modification on the Structure, Physicochemical Properties and Digestibility of Corn Starch

Corn starch was modified through autoclave treatment (autoclave temperature/time: 127 ℃/32 min) and ultrasound assisted autoclave treatment (compression heat temperature/time: 110 ℃/26 min) to explore the effects of ultrasonic assisted autoclave modification on its resistant starch content, structure and properties. And the influence of modification treatment on the changes of its resistant starch content was evaluated by analyzing the structure, physicochemical properties and digestive characteristics. Results showed that the modification treatment resulted in irregular lumps of starch granules with notches on the surface and the shift in the crystal form from A-type to V-type, which changed the short-range ordering of starch but not accompanied by the formation of new functional groups and chemical bonds. The hydrolysis rate of modified corn starch was significantly lower than that of corn starch (P<0.05), while the water separation rate, transparency and solubility were significantly higher than that of corn starch (P<0.05). Compared with autoclave alone, higher resistant starch content, amylose content, transparency, and anti-digestion were observed in corn starch as a result of ultrasonic-assisted autoclave modification, but decreased freeze-thaw stability was observed. The ultrasonic assisted autoclave modification effectively improved the resistant starch content and anti-digestibility of corn starch by changing the structure and physicochemical properties. Modified corn starch can be used as an ingredient with a low glycemic index in starch-gelatinized food as well as in staple and side dishes.