Taguchi L8 Optimization of Processing Conditions in Designing a Functional Food Product: An Antioxidant-Rich Tomato Soup with Preserved Melatonin-Serotonin- l -Tryptophan Synergy

Abstract The indoleamine antioxidant triad (melatonin, serotonin, and l-tryptophan) displayed in vivo bioavailabilities in rat models when delivered through a tomato-based soup. The present study focuses on the development of this antioxidant-rich tomato-based soup (with preserved antioxidant synergy) through rigorous optimization of processing conditions and comprehensive physicochemical characterization of the finished product, including proximate composition and rheological properties. A Taguchi L8 (eight experimental combinations) orthogonal experimental design was employed to investigate the effects of processing temperature (50–60 °C), guar gum concentration (0.25–0.35%), and processing time (8–10 min) on indoleamine retention and antioxidant synergy effect (SE). Signal-to-noise ratio analysis (larger-the-better criterion) indicated that processing time exerted the most significant influence on indoleamine stability (F = 227.5 for melatonin; F = 171.1 for serotonin; p < 0.05); whereas, temperature and guar gum concentration showed comparatively lesser effects. The optimized processing conditions─processing temperature of 60 °C, addition of 0.35% guar gum, and processing time of 8 min─resulted in maximum retention of melatonin (6.85 μg g–1 dwb), serotonin (17.12 μg g–1 dwb), and l-tryptophan (22.43 μg g–1 dwb) in the designer tomato soup. The same also demonstrated effective preservation of indoleamine stability and antioxidant synergy (SE value 1.01).