# Non-Thermal Technologies in Food Processing: Implications for Food Quality and Rheology
## 7 Utilisation of Non-Thermal Food Processing Technologies
### Non-Thermal Technologies in Solid and Semi-Solid Foods  
In solid and semi-solid food, the non-thermal technologies are primarily focused on texture preservation, improved rheological properties, and microbial inactivation. HPP is a very effective non-thermal technology that concurrently subjects solid and semi-solid foods of any composition, shape, or size to an even pressure. Unlike conventional thermal treatment, which causes irregular heating with a potential decline in the food quality, HPP ensures a homogeneous pressure distribution, which allows for the product to retain its original shape when the isostatic pressure has been released with little textural changes [199]. HPP enhances the textural characteristics by inducing protein denaturation and gelation, leading to increased firmness, elasticity, and juiciness, which are key attributes for consumer acceptability [106]. As opposed to conventional thermal treatment, which would lead to protein denaturation and moisture loss, HPP preserves the structure of food ingredients with microbial inactivation [80]. In addition, HPP allows for the heating of food through compression, enabling increased microbial inactivation, particularly in spore-forming bacteria such as _Clostridium botulinum_, when used in conjunction with pressures of 500-700 MPa and temperatures of 45-50 \({}^{\circ}\)C [98; 200]. Compared to traditional thermal processing, HPP does not alter the sensory and nutritional properties of foods, with the freshness, flavour, texture, and colour being retained while vitamin loss and chemical changes are minimised [199]. This renders HPP as a superior choice for quality preservation in products. However, despite its advantages, commercial adoption has been relatively recent due to the cost of the equipment and the technical expertise required for implementation. PL and IOR are also applied to minimise microbial populations in solid foods while preserving sensory characteristics. PL is particularly ideal for retaining the firmness, texture, and appearance of fresh fruits and vegetables, whereas IOR is frequently used in food sterilisation. While thermal processing like autoclaving leads to a severe loss of nutrients and texture, PL and IOR are a less harsh option that can preserve the food quality [121; 147]. Yet, IOR could, at high concentrations, impact the sensory characteristics, and optimisation should, therefore, be carried out with caution to balance microbial safety against the food quality and integrity [193]. These non-thermal technologies possess great efficiency in balancing microbial safety with the desirable textural and structural attributes of foods and are, hence, highly valued in modern food industries. Challenges such as high capital costs and limitations in the treatment of certain food matrices must be overcome for the full exploitation of their potential toward the enhancement of food rheology and quality. Table 1 presents the application of these non-thermal technologies in food processing for improved rheology and quality. \begin{table}
\begin{tabular}{p{108.4 pt} p{108.4 pt} p{108.4 pt} p{108.4 pt} p{108.4 pt}} \hline
**Food Type** & **Technology Used** & **Observation** & **Quality and Rheological Effects** & **Parameters** & **References** \\ \hline Red cherries (_Prunus avium_ var.