Preparation of ovine and caprine beta-lactoglobulin hydrolysates with ACE-inhibitory activity. Identification of active peptides from caprine beta-lactoglobulin hydrolysed with thermolysin

Ovine and caprine beta-lactoglobulin (beta-Lg) were isolated from sweet and acid whey by precipitation with trichloroacetic acid. This method allowed a rapid purification of ovine and caprine beta-Lg with high purity (higher than 92%), when starting from acid whey. These beta-Lg preparations were digested with trypsin, chymotrypsin, proteinase K and thermolysin and the angiotensin converting enzyme (ACE)-inhibitory activity was determined at different hydrolysis times. Consistently, higher activity was found in the hydrolysates prepared with enzymes of microbial origin. Four novel ACE-inhibitory peptides were purified and identified from caprine beta-Lg hydrolysed with thermolysin. The identified peptides were caprine beta-Lg f(46-53), f(58-61), f(103-105), and f(122-125), with ACE-inhibitory activities (IC50) that ranged from 34.7 to 2470 muM. The structure of the identified active peptides in relation to previous structure-activity studies is discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.