Son, Ezgi (2025) Optimal Shape Design of Ohmic Heating Chambers. [Tesi di dottorato]

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Abstract

Ohmic heating (OH) is an innovative thermal processing of foods in which internal heat is generated within the food material by passing an alternating electric current. This technique makes it possible to produce uniform, volumetric heating of the whole food sample. As a result, faster heating, higher product quality, and lower energy consumption are achieved when compared with conventional thermal treatments. In general, OH is used in traditional processes like pasteurization and sterilization. Originality lies in the innovative aspects of OH, which are the focus of this thesis. A series of optimization studies through mathematical modelling is conducted to study critical parameters that would affect the resulting heating profiles: chamber geometry, particle shape, size, and particle location. The results highlight that these parameters effect the temperature distribution, and geometrical and positional change of the particles give steep temperature gradients inside the food matrix. Other than that, the geometry of the chamber became an important issue, since it is directly related to the uniformity in heat transfer and efficiency of the global process. Besides the thermal effect, the non-thermal effect of OH, namely electroporation, was studied in brining of meat processes as a pretreatment. The electroporation effect generated by OH increases the coefficient of salt diffusion and reduces brining time; hence, it has the potential to enhance mass transport process and improve pretreatment efficiency in food processing. Further application of OH was done in multi-phase systems, such as meatball-puree mixtures, where homogeneous heating is vital to product quality and safety. The main observation was the non-uniform heating between the particulate and the surrounding medium due to mismatches in electrical conductivities of the dispersed and continuous phases, further emphasizing the need for precise handling of electrical and thermal properties to avoid hot spots. Future research should be directed toward the integration of OH technology with smart manufacturing and automation for real-time monitoring and dynamic control to attain an optimum and homogenous heating pattern. Further development with respect to the non-thermal effects of OH could lead to better nutrient retention, microbial inactivation, and other benefits in various minimally processed foods and position OH as one of the leading-edge methods of efficient food processing.

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