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The effects of high power ultrasound of 24 kHz and ultrasound bath of 24 kHz frequency on the textural and pasting properties of corn starch suspensions was examined. Suspensions were treated with different intensities and treatment times (15 min and 30 min) using an ultrasound probe set and bath. The treatments with high power ultrasound probes caused a significant lowering of the starting gelatinisation temperatures of corn starch. The ultrasound treatment caused disruption of starch granules by cavitational forces and made the granules more permeable to water. The highest viscosity was observed for the treatment with 300 W probe. Also, a statistically significant increase in solubility in water (20°C) was observed, being caused by the disruption of starch granules and molecules by ultrasound treatment. When applying more powerful ultrasound, starch granules, specifically in the amorphous region, are much more mechanically damaged. The texture profile analyses of the starch gel prepared from the suspensions that had been treated with ultrasound probe presented higher hardness and higher values of adhesiveness and cohesiveness when compared with untreated suspensions or those treated with ultrasound bath. Micrography showed an obvious impact of ultrasound on the structure of starch granules. Ultrasound treatment ruptures and mechanically damages the starch granules causing collapse of cavitation bubbles which induces high pressure gradients and high local velocities of the liquid layers in their vicinity.

The aim of this research was to investigate the impact of high‐intensity ultrasound as pretreatment on the duration of drying and texture characteristics of infrared‐dried pear slices using different amplitudes. Ultrasound device with a power capacity of 400 W, working at a frequency of 24 kHz and amplitudes of 25, 50, 75 and 100%, was used for pretreatment. Drying was performed in an infrared dryer at 70C. The results obtained showed how application of ultrasound with various amplitudes influenced the shortening of the drying time and allows the elimination of more water from the pear slices. The results showed that hardness of samples gradually decreased (from untreated sample [104.72 N], 50% of amplitude [93.461 N] to 100% amplitude [62.206 N]) with an increase in ultrasound intensity and that all process parameters had significant influence on the textural properties of pear slices (hardness, elasticity and work required for chewing). Practical Applications Drying in food technology is usually based on the use of conventional methods such as heat exchange by conduction or convection, which may have negative effects on textural issues of final products. In order to achieve final products of high quality, new and sophisticated techniques for food treatment are required. One of such methods is the power ultrasound‐aided drying. This method is proven efficient for preserving main characteristics and quality of products, and additionally leads to shortened drying time.

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