Heating Performances of Tomato-Based Dressing Sauces Undergoing Moderate Electric Fields

Moderate electric fields (MEF) heating belongs to electro-assisted heating technologies. MEF involves the use of electrical alternate current, which is forced to pass through a food material, applying an electrical potential gradient up to 1000 V/cm with frequency going from 1 Hz to 1e4 Hz. In MEF assisted heating, the electrical current dissipates heat inside the food product, thus overcoming the heat transfer resistances due to convection or conduction. Tomato based dressing sauces represent a worldwide appreciated food product. Industrially heat transfer operations related to the production of such dressing sauces are based on the use of hot water or steam as heat carriers. Exploring new heating technologies able to shorten production times, can contribute the shift of food industry towards more efficient and less environmentally impacting processes. In order to assess the applicability of MEF heating to tomato-based dressing sauces, three different products were analysed. Namely, tomato sauce, tomato sauce with eggplant, tomato sauce with minced meat were considered. Tests were performed in a custom MEF system imposing an electrical potential difference from 50 V to 80 V. Given the fair even temperature distribution, a macroscopic transient energy balance was used to estimate the electrical conductivity of the considered products and, furthermore, the model of the electrical conductivity as a function of the temperature. Results showed that the investigated products are characterized by electrical conductivity in the range of 1 to 5 S/m, making these sauces keen to MEF heating treatment and opening new opportunity to exploit such heating technology in the preparation and processing of tomato-based dressing sauces.