Antihypertensive whey protein concentrate hydrolysates find nutraceutical beverage applications.

Hypertension is a significant controllable risk factor that's associated with various cardiovascular diseases, such as myocardial infarction, stroke and heart failure. Angiotensinogen is a serum alpha-globulin that is synthesized in the liver. It is cleaved by renin to form angiotensin I. Angiotensin I is eventually hydrolyzed by the angiotensin-I-converting enzyme (ACE) to angiotensin II, which is a potent blood vessel constrictor--a vasoconstrictor.

It has been reported that the in vitro incubation of milk proteins with proteinase preparations can result in the release of ACE inhibitory peptides, which could keep blood vessels from narrowing. Scientists at Washington State University examined three commercial proteases, Validase BNP L, Validase FP II and Multifect Neutral, for digestion of 20% solutions of 80% protein whey protein concentrate (WPC80) to determine if there is any production of ACE inhibitory activity.

The scientists used enzymes at 1% (w/w) and incubated them at pH 7 for up to 200 minutes at 50 C. The degree of hydrolysis (DH) was monitored using a TNBS assay. ACE inhibition was measured using hippuryl-L-histidyl-L-leucine as the substrate. Incubation for up to 15 minutes produced a DH of 0.5% to 3% and maximum ACE inhibitory activity.

Validase FP II produced a 61% rate of inhibition with an IC50 value of 4.1 mg per ml. Validase BNP L produced a 46% inhibition rate with an IC50 value of 5.7 mg per ml. Multifect Neutral produced a 32% inhibition rate with an IC50 value of 8.1 mg per ml.

Investigators selected the Validase BNP L hydrolysate for use in developing a nutraceutical beverage because the enzyme is readily inactivated by lowering the pH. A test beverage was manufactured in a batch process. In the process, the WPC80 and enzyme were incubated for 15 minutes. The enzyme was inactivated by lowering the pH to 4.0 with citric acid.

The hydrolysate solution was centrifuged to remove any insoluble WPC80. Water, potassium citrate, sugar, pectin and flavor were added. The beverage was ultra-pasteurized and bottled. ACE inhibition was measured in the final beverage, indicating that the hydrolysate maintained most of its activity through various processing steps.

Further information. Joe Powers, Department of Food Science and Human Nutrition, Washington State University, FSHN 226, P.O. Box 646376, Pullman, WA 99164; phone: [phone]; fax: [phone]; email: [e-mail].