Optimization of a Dry Peeling System for Tomatoes Using Approximate Solutions

Abstract

In recent years tomatoes have been peeled using steam and lye. Both are costlier, less environmentally friendly and highly polluting techniques. Thus, more sustainable alternatives should be sought after. Among these alternatives is radiative heating. To appropriately design the system for dry peeling, several typical operational characteristics of the process in issue must be estimated. The analytical model presented allows estimates to be made through closed-form relationships between the parameters involved. The analysis is based on the use of an appropriate theoretical model, which facilitates the solution to the proposed problems. Through the approximate solution of the analytical problem, we will analyse: the angular speed Ω, the temperature fluctuations ΔT0, the process time tc. These estimates are then used to derive a specific model for a control of process. The temperature profile (through an approximate solution) associated with the process that provides the optimum peel quality was utilized as a guide for the regulation system. A control system used the code to extract a specific temperature, and based on surface tomato temperature readings, controlled a brushless motor using a logic strategy. The regulating system can adjust the rotation speed, and hence the heating intensity, even under less than perfect operating conditions in order to obtain the appropriate profile temperature. The controlled temperature profile yielded an average temperature of 66.3°C, while the reference case yielded a temperature of 67°C. Additionally, it was found that the temperature inaccuracy decreased with each rotation, ranging from 2.5 °C at 2π to 0.3 °C at 16π. As a result, the peeling procedure is standardized in time, temperature, and quality.