Enhancement of physicochemical properties and antioxidant activity of carob-based dark chocolate as a cocoa powder substitute

Carob (Ceratonia siliqua L.), a caffeine-free and fiber-rich legume, has potential as a functional substitute for cocoa powder in dark chocolate (DC) products. This study aimed to investigate the effects of substituting cocoa powder with carob powder (0–100%) on the physicochemical, antioxidant, and sensory properties of DC samples. Five DC formulations were produced by varying the carob-powder-to-cocoa powder ratio and were analyzed for pH, fat, protein, polyphenol, and flavonoid contents, antioxidant activity (IC₅₀), texture, color, particle size, melting behavior, polymorphism, microstructure, and sensory acceptability. The results showed that increasing carob content enhanced antioxidant activity (IC₅₀: 70.61–105.87 ppm) and polyphenol levels (7.70–18.47 mg GAE/g), while reducing fat (−5.7%) and protein (−80.2%). Carob-based DCs had lighter colors (ΔE: 1.20–2.68), softer textures (up to 54% reduction in hardness), and a tangier flavor. All formulations maintained stable V – VI polymorphic crystals and fine particle sizes (D₅₀: 70.67–77.61 µm). Sensory tests (5-point scale) indicated that DC with a 50:50 carob powder-to-cocoa powder ratio (DC50) had the highest overall acceptability (score: 3.91), with a balanced flavor and texture. These findings suggest that carob powder can be used as a functional and health-conscious alternative to cocoa powder in dark chocolates, offering enhanced antioxidant properties without compromising consumer acceptance.