Bioactive Recovery from Watermelon Rind Waste Using Ultrasound-Assisted Extraction
Sania Zia, Moazzam Rafiq Khan, Rana Muhammad Aadil, Ilce Gabriela Medina‐Meza
Abstract
In response to the imperative to address food and agricultural waste and promote environmental sustainability, this study investigates the transformation of watermelon rind waste into a valuable resource. We extract polyphenols and antioxidants from freeze-dried watermelon rind across four cultivars (Crimson Sweet, Black Prince, Black Chairman, and Sugar Baby) using ultrasound-assisted extraction. Solvent selection, based on a preliminary experiment, was optimized through the response surface methodology (RSM), fine-tuning the solvent concentration and sonication time. The RSM effectively modeled our responses ( R 2 > 0.90), confirming its suitability for optimization. Applying the optimized parameters (80% solvent concentration and 20 min of sonication) to the rinds yielded extracts rich in flavanols (10–30 mg/g) and phenolics (1–2.5 mg/g), with high DPPH (22–40 mg Trolox/g) and FRAP (26–42 mg ferrous sulfate/g) antioxidant activities. Furthermore, fatty acid and phytosterol profiles of watermelon rinds were reported, demonstrating their potential applications in food, pharmaceuticals, nutraceuticals, and industry.