Mineral enrichment, functional and sensory properties of whole-watermelon juice formulations using pulp, rind, and seed fractions

Abstract

Fruit seeds and rinds are nutrient-dense yet underutilized sources of essential minerals and bioactive compounds. The limited exploitation of by-products from Crimson Sweet watermelon (Citrullus lanatus), particularly the rind and seeds, results in substantial loss of valuable nutritional biomass. This study examined the mineral-enhancement potential, functional traits, and sensory quality of whole-watermelon juice formulations prepared by systematically combining pulp, rind, and seed fractions. A D-optimal mixture design produced nine formulations with pulp (45–70%), rind (20–45%), and seed powder (0–10%). Functional properties, mineral content, and sensory attributes were evaluated using standard analytical methods, validated FAAS protocols, and hedonic sensory assessment. Results showed that adding rind and seed significantly (p < 0.05) decreased swelling power and solubility but increased water absorption capacity, indicating better functional performance. The optimal range was achieved in formulations containing 45–70% pulp, 20–45% rind, and 10% seed, yielding calcium (64.63–84.12 mg/100 g), phosphorus (486.21–512.07 mg/100 g), sodium (38.00–78.15 mg/100 g), and potassium (629.00–649.10 mg/100 g). Significant differences (p < 0.05) were observed in consumer acceptability of watermelon juice formulations across appearance, aroma, taste, flavour, mouthfeel, and overall liking, with P 70 :R 25 :S 5 (70% pulp, 25% rind, 5% seed) achieving the highest overall acceptability, demonstrating that moderate rind and seed inclusion can enhance sensory quality without compromising consumer preference. Overall, the results show a 3- to 73-fold increase in key minerals while maintaining desirable functional and sensory traits, supporting the valorization of watermelon by-products for the sustainable development of nutrient-rich functional drinks.