No abstract

No abstract

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.

No abstract

Production of extrudates from cereals is an oftenused technological process in today's world food industry. Extrudates from corn flour produced using the twin-screw extrusion process and enriched with whey protein concentrate represent high-quality source of proteins and fats. Whey protein concentrate (WPC) as a valuable source of proteins and minerals is one of the highest-quality components for possible extrudate enrichment. In this paper, the influence of various WPC addition and some extrusion process parameters such as feed moisture content (Q H 2 O ) on physicochemical properties of directly expanded corn flour extrudates manufactured in twin-screw corotating extruder was investigated. Whey protein concentrate was added in the following ratios 7.5%, 15% and 22.5% and water in 10.08, 12.18 and 14.28 L/h. Final composition of products is determined with measuring of protein, fat and water shares, water absorption index (WAI) and water solubility index (WSI). With added WPC and with increase of water volume flow, there was a significant rise in total protein, fat and water content in final products, as well as lowering of WSI and rising of WAI indexes. The statistical analysis of the obtained data shows that the lowest WSI and the highest WAI had samples with the largest share of WPC (22.5%) and water volume flow of 14.28 L/h. Colour is measured for each sample, and results were represented with hue angle (H), chroma (C) and lightness (L) values. Process parameters, WPC and Q H 2 O

Tribomechanics is a part of physics that is concerned with the study of phenomena that appear during milling under dynamic conditions. Tribomechanical micronization and activation (TMA) of whey protein concentrates (WPC) and zeolites (type clinoptilolite) were carried out. Samples of powdered WPC and zeolite were treated with the laboratory TMA equipment. The treatment was carried out at two various rotor speeds: 16,000 and 22,000 r.p.m. at ambient temperature. Analyses of the particle size and distribution as well as the specific area and scanning electron microscopy were carried out on the powdered WPC and zeolite, before and after the TMA treatment. Suspensions of the WPC and zeolite were treated with ultrasound, just before determining the particle size distribution, at 50 kHz. The results showed that tribomechanical treatment causes significant decrease in particle size, change in particle size distribution and increase in specific area of WPC and zeolite. These changes of the treated materials depend on the type of the material, the level of inserting particles, the planned angle of the impact, internal rubbing and the planned number of impacts. The effects found became stronger as the rotor speed of the TMA equipment increased (16,000 to 22,000 rpm). Ultrasonic treatment of suspension of tribomechanically treated WPC resulted infurther breakdown of partly damaged protein globules as proved with the statistic analyses. No further changes in their granulometric composition were caused by ultrasonic treatment of a suspension of tribomechanically treated zeolite.

No abstract