Effect of sonication on physical, chemical and functional properties of oat starch

Recently there has been a growing interest toward the utilization of sonication considering its high efficiency and accessibility. High power ultrasound waves make sinusoidal moves through the liquid environment and create unstable vacuum bubbles which are growing in size till disrupt. Their disruption lead to the creation of spots of very high velocity and temperature. The large particle and molecules located near this spots degrade and produce particles or molecules of smaller size. It is generally accepted that ultrasonic degradation of polymers in solution is of mechanical nature rather than thermal in origin, and that the stresses induced in polymer molecule are caused by the friction forces generated by the relative movement of the molecules of solvent and polymer as a result of the collapse of cavitation bubbles. In this research, the effect of different ultrasound power and temperature on the oat starch properties was investigated.

Extracted oat starch with determined chemical composition was sonicated by using a 20 kHz ultrasound probe at 150 and 350 W power at 25 and 50 ̊C for 10 min. Sonicated oat starches were recovered by centrifugation and drying. Afterward, the various chemical and physical properties of native and sonicated oat starch such as solubility, swelling power, thermal properties, textural properties, water and oil absorption capacity and retrogradation were investigated. under different combination of heat and sonication power were investigated.

Ultrasound treatment had significant effect on oat starch properties. The results indicated that increasing the power and temperature, enhance the effect of ultrasound on different oat starch properties. Swelling power, solubility, gel clarity, and gelatinization temperature parameters were significantly increased due to the higher power and temperature of sonication. Retrogradation of sonicated starch samples was significantly lowered as compared to naïve oat starch samples. Gels prepared from sonicated oat starch had significantly softer texture compared to the native oat starch gels. These changes could be mainly due to disruption of amorphous and weaker crystalline structures and also the degradation of high molecular weight molecules to molecules of smaller size. Swelling power, solubility, gel clarity and gelatinization temperature were increased while the reverse trend was observed for gel hardness and retrogradation. This changes could be mainly due to the destruction of amorphous and weak crystalline structure of starch granules.

These results declared that oat starch properties would be affected by ultrasound treatment, And as compared to the control, it’s revealed that the effect of higher power and higher temperature were more pronounce that lower temperature and lower powers. Finally, regarding the proper characteristics of starches modified under the sonication condition of 350 W power at 50 ̊C (e.g. soft and stable structure of gel with low tendency toward retrogradation and opacity), this treatment is recommended as the optimum condition.