Power Ultrasound Enhanced One-Step Soaking and Gelatinization for Rough Rice Parboiling

The conventional parboiling of rough rice is a lengthy process that takes 24-28 h to complete. It would be beneficial to the industry if the processing time could be reduced. The objective of this study was to develop an ultrasound based one-step protocol for soaking and gelatinization during rice parboiling. The gelatinization temperature was measured by alkali (KOH) degradation and found to be 72 degrees C. The combined soaking and gelatinization was conducted at 75 degrees C with or without sonication (control). The moisture content during soaking was measured following the AOAC oven method. Starch gelatinization was evaluated by differential scanning calorimetry (DSC). Moisture content after 3 h of ultrasonic soaking (48.6% w.b.) was equivalent to 10 h conventional soaking (44.0% w.b.), indicating that ultrasound reduced some 70% of soaking time. DSC showed that the retrogradation peaks (Tr) values for 80 degrees C soaking and ultrasonic horn (US. horn) soaking, which were accomplished during 4 h, was 53.8 degrees C and 53.5 degrees C, respectively. This showed that US. horn soaked samples at 75 degrees C partially gelatinized at the same time frame (4 h) with the samples soaked at 80 degrees C. This study showed the feasibility of ultrasound to enhance the rice parboiling by reducing processing time.