Acid whey proteolysis to produce angiotensin-I converting enzyme inhibitory hydrolyzate

Abstract

α-Lactalbumin (ALA) and β-lactoglobulin (BLG) are the main proteins in acid whey and proteolytic digestion of these proteins provides a source of peptides that inhibit angiotensin-I converting enzyme (ACE-I). Enzymatic hydrolysis of acid whey proteins using cysteine peptidase enzyme extract (antiacanthain) from ripe Bromelia antiacantha Bertol fruit was investigated. The effect of pH on hydrolysis kinetics of ALA and BLG by antiacanthain was analysed at 50 °C. Antiacanthain had a high catalytic efficiency for ALA (1.3 × 104 M−1 s−1) and BLG (1.7 × 104 M−1 s−1) at pH 9.2. The effect of temperature and amount of antiancanthain (enzyme to substrate ratio or E/S) on acid whey hydrolysis were studied by measurement of degree of hydrolysis (DH) and protein degradation profile evaluated by tricine–sodium dodecyl sulfate-polyacrylamide gel electrophoresis (tricine–SDS-PAGE). Optimal acid whey hydrolysis was at pH 9.2, E/S = 1.0 (U/mg) and 50 °C. BLG was degraded faster than that of ALA, but after 30 min hydrolysis almost all BLG and ALA were degraded and new bands corresponding to peptides with a mass lower than 3.0 kDa appeared. Fractions of acid whey (DH = 12.3%), ALA (DH = 17.3%) and BLG (DH = 30.6%) hydrolyzates showed ACE-I inhibitory activity. Results also suggest that most inhibitory activity might be due to low molecular weight peptides from ALA, since 3 kDa permeate of ALA hydrolyzate showed the highest IC50 value (1.7 ± 0.4 µg/mL). Interestingly, low molecular weight peptides from both ALA and BLG had low immunoreactivity levels, monitored by latex agglutination tests, suggesting that these peptides could be safe for use by those with strong allergic responses. Results indicate that antiacanthain can be used as an enzymatic preparation for acid whey hydrolysis. The potential use of this hydrolyzate for manufacture of health-promoting products of high added value is discussed.