# Application of Ultrasound Homogenization in Milk Ice Cream Mixes
## 1 Introduction  
Recent developments in the field of the food industry have led to a renewed interest in using ultrasound, which has been a known technique for many years. The generalizability of much-published research on the characteristics of ultrasound shows that it is a relatively cheap, simple, fast, non-toxic, and energy-saving technology [1, 2]. The broad use of the term ultrasound is equated with sound waves exceeding the audible frequency range, i.e., greater than 20 kHz. The effects of ultrasound are associated with acoustic cavitation. It causes physical and chemical changes in liquid products by generating extreme physical forces, counting acoustic streaming, turbulence, shock waves, microjets, and shear forces. Then, acoustic cavitation occurs when the waves pass through a liquid medium on the grounds of creating interactions between ultrasonic waves, liquid, and dissolved gas. The cavitation bubbles are able to grow through the compression and decompression of ultrasound waves to obtain their critical sizes, and, after that, they collapse. Therefore, this collapse generates extremely high temperatures and also pressure regions, which produce high shear energy waves and turbulence [1, 3, 4]. Ultrasound has been applied in dairy processing for many years, such as the enhancement in whey ultrafiltration, reduction in viscosity, homogenization of milk fat, and crystallization of ice and lactase for cutting cheese blocks. Furthermore, ultrasound has been successfully aimed at reducing processing time or enhancing the quality of dairy products [5, 6]. Additionally, numerous studies have attempted to explain the phenomenon ofthe application of ultrasound in ice cream production. First and foremost, using ultrasound during freezing has many beneficial aspects, such as enhancing the nucleation rate and the rate of crystal growth; therefore, a decrease in the ice crystal size and freezing time may occur [7; 8]. Based on the research of [PERSON] et al. [9], using ultrasound during the freezing of mango sorbent, it was proven that the combination of ultrasound treatment and stabilizers resulted in the formation of a favorable crystal structure, around 9 \(\upmu\)m. Moreover, in other studies, ultrasound was used during the pasteurization of ice cream, and it was concluded that ultrasound during the pasteurization process could be used instead of traditional pasteurization, with no changes to the ice cream [10]. The mentioned examples of using ultrasound in ice cream production have great potential. Together, these results also provide significant insights into using ultrasound during the different steps of ice cream production, for instance, homogenization, due to the fact that ultrasound homogenization may narrow particle size distribution and, therefore, improve the stability of the emulsion on the grounds that forces during acoustic cavitation such as turbulence, mixing, and shearing can disrupt fat globules and simultaneously reduce their sizes [1; 7]. Moreover, ultrasound homogenization offers an improvement over conventional methods due to the fact that emulsions after this method can be characterized by particles in the sub-micron range with extremely narrow particle sizes. Additionally, such emulsions are more stable, and even using surfactants is not necessary. Also, the energy that is needed to produce emulsion by ultrasound homogenization is less than that which is needed when using conventional homogenization [2]. Interestingly, the amount of fat and its structure may contribute to forming the ice crystal structure by forming less space for the crystal, and then smaller ice crystals may be obtained [11]. Furthermore, a detailed examination by [PERSON] and [PERSON] [12] shows that ultrasound homogenization beneficially influences the properties of ice cream such as the melting time.