Enhancing bioactive compounds and physicochemical properties of date palm juice for lyophilized palm sugar production Via a combined high-pressure and ultrasonic extraction

Abstract

Dates and their derivatives play a significant role in human nutrition, offering health benefits through valuable bioactive compounds such as polyphenols and flavonoids. Conventionally, the processing of date palm juice and the production of lyophilized date sugar involve heat treatments, which may degrade these sensitive compounds. This study aims to optimize non-thermal extraction methods—specifically High-Pressure Processing (HPP), Ultrasonic Processing (USP), and their combination, to enhance the yield and preservation of bioactive compounds in Deglet-Nour date palm juice. A full factorial experimental design was employed, varying processing time, pressure, ultrasound application, and freeze–thaw pretreatment across 18 extraction trials. The combined HPP-USP treatment for 30 min resulted in the highest total phenolic content (308.16 ± 0.27 mg GAE/100 g FW), total flavonoid content (328.54 ± 0.12 mg QE/100 g FW), and antioxidant activity (34.2 ± 1.05 mM Trolox/100 g FW). Additionally, this treatment achieved peak sugar concentrations, with total sugars at 699.71 ± 0.08 g/L and reducing sugars at 262 ± 0.05 g/L. These findings demonstrate that the synergistic application of HPP and USP significantly enhances the extraction efficiency and preservation of bioactive and nutritional compounds, offering a promising non-thermal alternative for the sustainable production of functional palm sugar.