Application of protease and high-intensity ultrasound in improving corn starch isolation

摘要

The conventional corn wet milling process requires a long steeping time and has environment concerns from sulfur dioxide usage. This project explored two new methods, protease digestion and combination of protease and high-intensity ultrasound, as possible alternatives for corn starch isolation within a shorter time and without the usage of sulfur dioxide. First, commercial acidic, neutral, and alkaline proteases of different concentrations were applied to corn flour at 50 for 1 hr with constant stirring to evaluate their effectiveness in isolating corn starch. The neutral protease digestion gave the highest yield and thus was used in combination with sonication. The corn flour slurry was subjected to sonication before, during, and after protease digestion. The starch yield ranged from 45.8 to 70.9% (starch dry basis) compared with 53.4% of the control with stirring only and 71.9% of the conventional method with sulfur dioxide and lactic acid steeping for 48 hr. The preferred combination was neutral protease digestion for 2 hr followed by sonication at 75% amplitude for 30 min. By combining neutral protease with high-intensity ultrasound, the efficacy of corn starch isolation was greatly improved, and sonication following protease digestion facilitated the separation process.