Recent trends in pre-processing and extraction of watermelon rind extract: A comprehensive review

Abstract

Watermelon rind contributes 30% (w/w) of overall fruit mass, mainly carbohydrates, fiber, and wax. The rind is often discarded due to its unappealing flavor. Several studies have proposed that watermelon rind waste can be utilized as high fiber flour, dietary supplement, food additive, and bio-sorbent material. However, before the offered product is developed, a proper technique of preprocessing and extraction methods are vitally important to be considered as they will determine the extraction yield quality. Thus, this review aims to provide an extensive overview of preprocessing and extraction techniques. A comparison of different procedures applied in the preextraction and extraction of watermelon rind is emphasized. Preprocessing parameters affecting extraction yields such as sample condition, drying condition, and grinding and grading technique are discussed. Several extraction techniques, including infusion, maceration, digestion, reflux, ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE), are correlated to identify their efficiency in extracting the phytochemical from watermelon rind. Factors that influence the extraction yield such as extraction temperature, solvent-to-solid ratio, extraction duration, and type of solvents are elaborated. Novelty impact statement: Preprocessing and extraction parameters affect the extraction yields of the watermelon rind. A comparison of extraction techniques to identify their efficiency in extracting the phytochemical from watermelon rind. Factors that influence the extraction yields of the watermelon rind.