To produce low sodium salt angiotension converting enzyme (ACE) I inhibitory peptides from sunflower seed meal protein,the digestion techniques with Ca(OH)2 as pH adjusting reagent (pHAR) was established and optimized.Assessed by degree of hydrolysis (DH),ACE inhibitory rate,and bitterness of peptides,trypsogen was chosen from six commercial proteases to use as digestive enzyme in this study.Based on enzymolysis reactions with NaOH or Ca(OH)2 solution as pHAR,it was observed that at same conditions of digestion except pHAR,the ACE inhibitory rate and DH of sunflower seed meal peptides (SSMP) with Ca(OH)2 as pHAR were higher than those with NaOH as pHAR,and the bitterness of two kinds of SSMPs were quite close.According to single factor experiments on substrate content (SC),trypsogen content (TC),pH value,digestion temperature (DT),and digestion time (Dt),and orthogonal test on pH,DT,and Dt,the optimal digestion conditions were determined as:SC 3.5% (m/v),TC 2.85% (E/S),pH 7.5,DT 45℃,and Dt 5 min.And the 50% ACE inhibitory content (IC50 value) of SSMP under the optimal condition was 6.06 mg/mL.