Sustainable Processing of Citrus By-Products: Influence of Drying on Bioactive Compound Recovery

Citrus processing generates substantial quantities of by-products, including peels and pulp residues, which represent valuable sources of bioactive compounds. The efficient recovery and characterization of these compounds are essential for the development of value-added ingredients and sustainable food applications. This study investigates the influence of different drying and extraction approaches on the recovery of bioactive compounds from grapefruit, orange, and lemon by-products. Citrus materials were subjected to conventional hot-air drying and freeze-drying, followed by ultrasound-assisted extraction (UAE) by use of 70% ethanol. The obtained extracts were characterized by determining colour parameters and ferulic acid (FA) content. Ferulic acid is a powerful antioxidant because it neutralizes the damage caused. In addition, near-infrared spectroscopy (NIR) was applied as a rapid and non-destructive analytical tool for the characterization of dried citrus materials and the evaluation of potential relationships between spectral features and bioactive compound content. The study aims to identify the processing conditions that maximize the recovery of FA while providing insights into the applicability of NIR spectroscopy for rapid assessment of citrus by-products using AI tools. The results may contribute to the development of efficient analytical approaches for the characterization and utilization of citrus-derived functional ingredients (re)used in the food and pharmaceutical industry.