Valorization of Second-Grade Watermelon in a Lycopene-Rich Craft Liqueur: Formulation Optimization, Antioxidant Stability, and Consumer Acceptance

Second-grade watermelons are a lycopene-rich by-product currently discarded despite their potential for valorization. This study aimed to develop a consumer-accepted alcoholic liqueur by alcoholic maceration of watermelon pulp, optimizing the formulation for lycopene retention, antioxidant activity, and sensory quality. Three pulp ratios (15, 20, and 25% v/v) were macerated in 39% v/v cane alcohol for 5 days at 20 °C. The 20% pulp formulation (T2) achieved the best balance of lycopene (8.6 mg L−1), DPPH antioxidant activity (580 µmol TE L−1), redness (CIE a* = 14.1), and overall acceptability (7.6/9). Under nitrogen-flushed amber glass, T2 retained ≥82% lycopene and ≤10% antioxidant loss after 90 days at 20 °C, following first-order degradation kinetics (Ea = 43 kJ mol−1). A minimum shelf-life of three months is projected under these experimental conditions. Life-cycle screening indicates 0.84 kg CO2-eq L−1, with a 1.9-year payback and 1.7 t CO2-eq savings per ton of rescued fruit compared to landfill. These findings demonstrate the feasibility of producing a shelf-stable, naturally colored craft spirit with watermelon flavor, aligning with consumer preferences and circular economy principles in the alcoholic beverage sector.