Recovery of phenolic compounds from orange juice solid waste by solid-liquid extraction

Abstract

In the orange juice production process, industries generate enormous amounts of solid waste, significantly rich in high added value bioactive compounds, such as phenolic compounds. In this work, the separation process of solid-liquid extraction has been investigated to recover the polyphenol content from orange juice production wastes. The parameters studied were the solid-liquid ratio, type of solvent, temperature, ultrasounds application, and extraction time. For aqueous extractions, the optimum experimental conditions were achieved with the aid of ultrasounds, a solid-liquid ratio of 1:10 (on a mass/volume basis), a temperature of 80 °C and 10 min of extraction time, obtaining 12.55 ± 0.09 mg gallic acid/g dry mass. However, for hydroalcoholic extractions, the optimal experimental conditions were obtained without ultrasounds, a proportion of 65% EtOH-water v/v, a solid-liquid ratio of 1:10, a temperature of 40 °C, and 1 h, achieving 15.9 ± 0.1 mg gallic acid/g dry mass. A full characterisation revealed that the Navel variety contained more phenolic compounds and lower concentrations of sugars and chemical oxygen demand than the other studied varieties. Liquid chromatography-mass spectrometry analysis, confirmed that the highest recovery of flavanones was obtained with the Navel variety, being hesperidin the dominant compound at a concentration of 366.2 ± 0.9 mg/L.