J Food Process Preserv. 2021;45:e15123. wileyonlinelibrary.com/journal/jfpp | 1 of 8 https://doi.org/10.1111/jfpp.15123 © 2020 Wiley Periodicals LLC. 1 | INTRODUCTION Watermelon (Citrullus lanatus) exemplifies as one of the most widely cultivated crops throughout the tropics and the Mediterranean regions (Paris, 2015). It has a smooth exterior rind (green, yellow, and/or pale green) and a juicy, sweet interior flesh (usually pink, orange, yellow, red, and sometimes green if not ripe) (Paris, 2015). Consumption of this quintessential fruit provides a good source of nutrients; such as vitamins B, C, and E, as well as minerals includ- ing phosphorus, magnesium, calcium, and iron and phytochemicals (Choudhary et al., 2015). There have been numerous reports that high dietary phyto- chemical consumption such as carotenoids and phenolic com- pounds may be beneficial in the prevention of oxidative damage to cells with a reduced risk of certain types of cancer, cataracts, inflammation, cardiovascular, muscular degeneration, and neu- rodegenerative diseases (Choudhary et al., 2015). Comparative research studies (Abu, 2018; Singh et al., 2016) have demon- strated that the natural phytochemicals occurring in watermelon possesses antioxidants along with anti-inflammatory and anti- hypertensive properties. Hong et al., (2015) hypothesized that watermelon would increase antioxidant capacity, thus reducing Received: 6 May 2020 | Revised: 19 November 2020 | Accepted: 22 November 2020 DOI: 10.1111/jfpp.15123 ORIGINAL ARTICLE Optimizing parameters on the antioxidant capacity of watermelon pulp using conventional orbital shaker and ultrasound-assisted extraction methods Beverly Tan Mei Chin 1 | Asgar Ali 1 | Hina Kamal 1 | Maysoun A. Mustafa 1 | Ghulam Khaliq 2 | Yasmeen Siddiqui 3 1 Centre of Excellence for Postharvest Biotechnology (CEPB), School of Biosciences, University of Nottingham Malaysia, Semenyih, Malaysia 2 Faculty of Agriculture, Lasbela University of Agriculture, Water and Marine Sciences, Uthal, Pakistan 3 Sustainable Agronomy and Crop Protection, Institute of Plantation Studies, Universiti Putra Malaysia, Serdang, Malaysia Correspondence Asgar Ali, Centre of Excellence for Postharvest Biotechnology (CEPB), School of Biosciences, University of Nottingham Malaysia, Jalan Broga, Semenyih 43500, Selangor D.E., Malaysia. Email: Asgar.Ali@nottingham.edu.my Yasmeen Siddiqui, Sustainable Agronomy and Crop Protection, Institute of Plantation Studies, Universiti Putra Malaysia, Serdang, Selangor, Malaysia. Email: yasmeen@upm.edu.my Abstract The current work had two objectives: to compare the total phenolic content (TPC) and antioxidant activity via two different extraction methods ultrasound-assisted extraction (UAE) and conventional orbital shaker (COS) extraction. Second, param- eters (solvent concentration, acidity, and sample-to-solvent ratio) influence the ex- traction of phenolic compounds. For each respective solvent, the sample-to-solvent ratio compared were 1:5, 1:10, and 1:20. The TPC of the pulp was extracted most effectively by UAE (38.69 mg). Total mean of extraction yield across all parameters showed that UAE (561.7 mg) was statistically more effective in DPPH radical scav- enging activity than the COS extraction (499.8 mg). However, the COS results from FRAP and ABTS yielded higher antioxidant activity. For all the tested assays, it was observed that the absolute methanol solvent and solvent-to-sample ratio of 1:20 were the most effective for extracting bioactive compounds from watermelon while solvent acidity had negligible effect. Novelty Impact Statement: Current work demonstrated how individual extraction characteristics (concentration, acidity, sample-to-solvent ratio, and method used for extraction) of watermelon “New Dragon A-117” variety is located in the phenolics and antioxidant characteristic map. Thus, providing information that can practically assist future product developers for their product formulation as a nutraceutical in a more sustainable and environment friendly manner.