Dark chocolate is a good source of dietary flavonoids, mainly comprised of (+)-catechin, (-)-epicatechin, and their oligomeric and polymeric procyanidins. Nevertheless, flavonoid content and antioxidant capacity are affected during chocolate manufacturing. In this study, the influence of manufacturing process of dark chocolate, particularly, roasting of cocoa beans (115-135 degrees C), conching (60-80 degrees C), and alkalization treatment (pH 7-9) was studied and the process conditions were optimized via Response Surface Methodology (RSM). Validation of the model accomplished applying the conditions generated by RSM. Considering the data obtained from the model; chocolate manufacturing process, particularly increasing alkalization degree and roasting temperature significantly reduced phenolics and related antioxidant capacity (p < 0.05). Nevertheless, increasing conching temperature was insignificant (p > 0.05) since higher temperature leads to a shorter required processing time. (C) 2015 Elsevier Ltd. All rights reserved.