Quality attributes of alkalized dark chocolate from Forastero cocoa nibs

The alkalization of cocoa is widely applied to modulate flavor, color, and acidity; however, its influence on Indonesian Forastero cocoa at the nib stage remains insufficiently characterized. This study examined the physicochemical, functional, and sensory attributes of dark chocolate produced from alkalized nibs treated with potassium carbonate (K₂CO₃) under four conditions (1–3%, 20–30 min, at room temperature or 60 °C). Alkalization significantly increased pH (from 5.09 to 8.47) and reduced titratable acidity (up to 63.5%), while promoting marked darkening through reduced L*, a*, and b* values and elevated ΔE. Bioactive compounds were notably affected, with total polyphenols declining by 1.1–21.5% and flavonoids by 5.5–21.2%, lowering antioxidant activity (IC₅₀ = 88.46–112.81 mg/L). Sensory profiling showed decreased bitterness, astringency, acidity, and fruity notes, while intense treatments increased alkaline flavor and lowered overall acceptance. Multi-criteria decision analysis identified moderate alkalization (3% K₂CO₃, 30 min) as optimal, yielding chocolate with balanced attributes and strong antioxidant activity (IC₅₀ = 97.7 mg/L). Pearson correlation revealed associations between increasing pH and reduced acidity, phenolics, antioxidant activity, and altered color. PCA distinguished samples by alkalization intensity, demonstrating relationships among acidity, phenolic composition, antioxidant activity, and color. Thus, controlled nib-level alkalization enhances Indonesian dark chocolate quality while mitigating degradation, offering insights for cocoa processing and premium product development.