Production of microparticulated protein is a new approach used to improve the function of whey proteins. In this process, particles in the range of 0.1-10 μm can be produced using shear force and heat treatment. The functional properties of proteins, such as emulsifying properties, water holding capacity, thermal resistance, and gel formation, improved after microparticulation. Therefore, they can be used as a fat mimic in dairy products such as cheese, pizza cheese, ice cream, sauces, etc. The aim of this study was to investigate the possibility of producing whey protein microparticles using ultrasound. Therefore, first, the whey protein isolate (WPI) solution was subjected to ultrasonic treatment at 300 and 600 W for 10 and 20 min. Then, the changes in turbidity, water holding capacity, solubility, emulsifying properties, sulfhydryl content, the amount of di-tyrosine, surface hydrophobicity, zeta potential, thermal properties, particle size, Fourier transform infrared spectrum, and protein microstructure were investigated. Finally, all data were statistically analyzed with SAS software at a significant level of p <0.05. The results showed that the turbidity and water holding capacity decreased with increasing power up to 300 W. However, increasing the power to 600 W was able to increase the turbidity and water holding capacity in WPI. Also, more prolonged time treatment at 300 W decreased the turbidity and water holding capacity while they were increased at the power of 600 W (p <0.001). Solubility was also affected by the power and time of ultrasonic treatment so that the solubility decreased with increasing time and power of ultrasound (p <0.001). The emulsifying capacity decreased in 300 W and increased in 600 W. However, applying ultrasound for a more extended period improved the emulsifying capacity, which was consistent with the observed trend in surface hydrophobicity (p <0.001). Applying ultrasound at higher power and times can significantly increase the amount of di- tyrosine and sulfhydryl content and surface hydrophobicity (p <0.001). eva‎luation of zeta potential showed an increase in electrical charge at a power of 300 W and a decrease in electrical charge with an increase in power to 600 W. By increasing the time of ultrasound treatment, the zeta potential decreased at first and then increased. eva‎luation of the Fourier transforms infrared spectrum showed that ultrasonic treatment can convert α-helices to β-sheets, especially after treatment at 600 W for 20 min. Also, an increase in the amount of free hydroxyl and hydrophobic groups was observed, which indicates the unfolding of the protein structure. Investigating the microstructure of ultrasound-treated WPI also indicated an increase in the protein unfolding and production of protein microparticles. In general, it can be said that ultrasound has been effective in reducing particle size in the micrometer range and improving the functional properties of whey protein isolate, such as water holding capacity and emulsion capacity, and stability. By controlling the temperature during the applying of shear force, it can be a suitable method for the production of protein microparticles.

نفيسه سلطاني زاده

ميلاد فتحي، مرتضي صادقي