Mathematical Modelling of Convective Drying of Orange By-Product and Its Influence on Phenolic Compounds and Ascorbic Acid Content, and Its Antioxidant Activity

Orange peel is one of the main by-products from juice processing, and is considered as a promising source of phenolic compounds with anti-carcinogenic, anti-inflammatory, anti-microbial and antioxidant properties. The drying is an essential step to ensure the storage of this by-product at an industrial level, in order to use it as a functional ingredient or as a nutraceutical. Thus, this research focuses on the evaluation of the effect of the convective air-drying process in orange by-products at three different temperatures (40, 60 and 80 degrees C) and air flows (0, 0.8 and 1.6 m/s) on the phenolic content (measured by HPLC-MS), the antioxidant activity (measured by DPPH, ABTS and FRAP), and the vitamin C content (measured by HPLC-UV/VIS). Moreover, the mathematical modelling of its drying kinetics was carried out to examine the orange by-product behavior. Among the tested mathematical models, the Page model reported the highest fit and the best drying conditions, which showed the lowest reductions were at 60 degrees C with an air flow of 1.6 m/s and taking 315 min.

Automated summary

Orange peel, a main by-product of juice processing, is a potential source of phenolic compounds with various beneficial properties. This study investigated the effect of convective air-drying at different temperatures and air flows on the phenolic content, antioxidant activity, and vitamin C content of orange peel. Mathematical modeling revealed the Page model as the most suitable for describing the drying kinetics, with optimal conditions at 60 degrees C, an air flow of 1.6 m/s, and a drying time of 315 minutes.