High ionic calcium concentration and the absence of casein macropeptides (CMP) in acid whey could influence the production of angiotensin-I-converting enzyme (ACE)-inhibitory hydrolysate and its bioactivity through the application of the integrative process. Therefore, the aim of the present study was to produce a hydrolysate from acid whey applying the integrative process. Process performance was evaluated based on protein adsorption capacity and conversion in relation to ACE-inhibitory activity (ACEi%) and ionic calcium concentration. Hydrolysates with high potency of their biological activity were produced (IC50 = 206-353 mu g mL(-1)). High ionic calcium concentration in acid whey contributed to ACE-inhibitory activity. However, low beta-lactoglobulin adsorption and conversion was observed. Optimisation of the resin volume increased the adsorption of beta-lactoglobulin significantly but with lower selectivity. The changes in conversion value were not significant even at higher concentration of enzyme. Several ACE inhibitors derived from beta-lactoglobulin that were identified before in sweet whey hydrolysates such as, IIAEKT, RAE, IVTQ LIVTQ L1VTQT, LDAQand LIVT were found. New peptides such as, SNICNI and ECCHGD derived from alpha-lactalbumin and BSA respectively were identified. (C) 2014 Elsevier Ltd. All rights reserved.