Solar drying is an unit operation whose technology is quite simple, whose cost is quite low, and which uses an abundant and renewable energy source which cannot be monopolized. In solar dryers, the pressure drop across the bed of drying material is low, so that electrical energy to be provided to the fans can be obtained by alternative sources, such as solar radiation itself, that is, by using photovoltaic energy. At first, forced convection in drying might increase drying rates; however, it might also increase the decomposition rates of bioactive compounds that provide color to foodstuff (due to the fact that the contact with atmospheric oxygen increases). Colorimetric parameters are a quality criterion, as it can provide evidence of the final consumers' acceptance. Another important factor for the decomposition of these substances is the solar radiation itself; hence, it is possible that a longer drying time, caused by the lack of forced convection, might expose the material to solar radiation for a longer time. In this context, the main objective of this project is the analysis of the influence of the operational conditions of a hybrid photovoltaic dryer which is being developed by the research group (Regular Research Grant FAPESP, process 2017/21890-5) onto colorimetric parameters of the dried product. Experiments with and without forced convection will be carried out. The measurement of the colorimetric parameters (CIELab scale) in samples taken periodically will allow to asses which mechanism affects more significantly the color variation on the dried product.
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