# Non-Thermal Technologies in Food Processing: Implications for Food Quality and Rheology
###### Abstract
These technologies, that can replace traditional thermal food processing techniques, are becoming very common as they emerge [5; 14]. These include physical processes such as a Pulsed Electric Field (PEF), High-Pressure Processing (HPP), Ionising Radiation (IOR), Ultraviolet and Pulsed White Light, as well as chemical treatments such as ozone treatment and cold plasma [6; 15; 16; 17; 18; 19]. These technologies limit the physical and chemical changes that occur during high-temperature processing, which also affects the bioactive components of foods [20; 21; 22; 23]. The main gain of using such non-thermal processes is to supply superior-quality food with characteristics of fresh food and improved qualities. Furthermore, they are environmentally friendly and economical, finding application in various foods with different rheologies, including juices [20; 24; 25; 26]. The global market for non-thermal food processing technologies has also continued to grow over the years, fueled by increasing consumer demand for minimally processed foods and industry efforts to enhance the food safety and quality [27]. For example, research, development, and manufacturing advances in HPP equipment have increased the production efficiency and operational stability. Geographic regions such as North America, Europe, and Asia have increased large-scale HPP capabilities because of this, with the value of the market standing at approximately USD 9.8 billion in 2015 and projected to grow to USD 54.77 billion by 2025, driven by an average production growth of 500,000 tons annually [27]. However, HPP food is still higher in its processing cost compared to traditional thermal pasteurisation, at 10.7 US\(\epsilon\)/L for orange juice compared to 1.5 US\(\epsilon\)/L for thermal pasteurisation [5]. The evaluation of the efficiency of certain non-thermal processing technologies to deactivate a range of spore-forming microbes and spores in various food products indicates that a combination of methods is needed [27]. For instance, it has been found that the complete inactivation of microbial spores such as _Bacillus pumilus_ and food safety can be achieved using a combination of supercritical carbon oxide and a co-solvent or an antimicrobial peptide [28]. However, the literature on the effects of thermal and non-thermal food-processing technologies on food properties is only just being explored in full, with limited studies such as the impact on the pectin structure and functionality in fruit- and vegetable-based products being published [29]. In 2021, a review on the impact of non-thermal processing on the structural changes of food components at the micro- and macroscopic levels was published [30]. The review focused on cold plasma treatment, high-pressure processing, irradiation, ultrasonication, a high-voltage electric field, pulsed light technology, and pulsed electric field technologies. Their impact on the structure of food such as protein structure modification was elucidated. Recently, an overview that focused on the impact of non-thermal processing techniques on the functional and physicochemical characteristics of food macromolecules has also been reported [31]. However, how the rheological properties of food products are influenced by non-thermal processing technologies is limited in the literature. Thus, an in-depth understanding of the effects of non-thermal food processing technologies on the food quality and rheology are critical for their application and design. From a functional perspective, the effectiveness of non-thermal processing depends on its interaction with the microstructure of the food products. Considering that the rheological properties of foods are a function of their microstructure [32], this microstructure is dictated by the complex physicochemical interactions and inter/intramolecular bonds between the food components. This contributes to a food's mixing attributes, mass and heat transport, and handling during processing. Hence, there is a correlation between the microstructure, rheology, and food processing.