The Effect of Ultrasonic Probe Size for Effective Ultrasound-Assisted Pregelatinized Starch

This study aimed to investigate the suitability of ultrasonication as an innovative pregelatinization method. The effect of ultrasonic probe diameter for effective pregelatinization on the physicochemical properties (color, solubility, and swelling), crystallinity (by X-ray diffraction), pasting properties (by rapid visco analysis, RVA), morphology (by scanning electron microscopy), and thermal behavior (by differential scanning calorimetry) of wheat and tapioca starch were compared. The ultrasonication power, temperature, frequency, time, and probe diameter were optimized via response surface methodology (RSM). The RSM results demonstrated that increasing temperature raised the solubility of ultrasound-pregelatinized wheat and tapioca starch, more than increasing the power input and treatment time. According to the RVA data, the cold and complex viscosity of the samples decreased as follows: ultrasound-assisted pregelatinized wheat starch (probe diameter, 100 mm) > ultrasound-assisted pregelatinized tapioca starch (probe diameter, 100 mm) > ultrasound-assisted pregelatinized wheat starch (probe diameter, 20 mm) > ultrasound-assisted pregelatinized tapioca starch (probe diameter, 20 mm). Overall, ultrasound-assisted pregelatinization using a probe of 100 mm in diameter had a stronger effect on wheat starch than tapioca starch. In conclusion, ultrasonication using a probe with a high surface area is a suitable method of starch pregelatinization.