Physical parameters kinetics during the drying process of quarters and halves cut tomatoes
University of Padua, Department of Land, Environment, Agriculture and Forestry, Viale dell’Università 16, Legnaro (PD), IT35020, Italy
Tomato drying is a time-consuming industrial process. Moreover, the prolonged use of high temperatures decreases the quality of tomatoes and increases the environmental footprint of the process. In most cases, drying is performed on halved tomatoes. Alternatively, the use of quarter tomatoes could guarantee a drying times reduction without compromising the final product quality. This work aimed at modelling changes in physical characteristics of half and quarter tomatoes. The drying tests were conducted at 50 and 60 °C. The kinetics of weight loss, colour change, and volume reduction were determined. Colour change was monitored through image analysis, while volume reduction using RGB-D reconstructions. Based on the results, an increase in the drying temperature and the use of quartered tomatoes allow a significant reduction in drying times. The loss of water kinetic allowed the determination of critical moisture. Between initial and critical moisture, loss of water occurred at constant rate (zero-order kinetic), while after that the rate decreased exponentially (first-order kinetic). The colour kinetics showed an initial constant rate followed by a linear increase for brown pixels. The variation of red pixels did not have a clear trend. Increasing the temperature there was no significant reduction in colour quality while quarter tomatoes showed a greater loss of redness than halved tomatoes. Furthermore, the temperature increase does not affect the volume reduction of the tomatoes. Increasing the temperature and the use of quartered tomatoes are simple solutions to reduce drying times. However, quartered tomatoes are less visually appreciable than halved tomatoes.