Protein Hydrolysate Batch Production with Angiotensin I-Converting Enzyme Inhibitory Activity from Egg Whites
WEN-DEE CHIANG1, MING-JAN LEE1, WEI-SHIANG GUO1 AND TSUN-CHUNG TSAI1*
1. Department of Food Science, Tunghai University, 181, Sec. 3, Taichung Port Rd., Situn District, Taichung 407, Taiwan, R.O.C.
(Received: July 6, 2006; Accepted: August 22, 2006)
ABSTRACT
Peptides derived from egg whites by thermolysin digestion were fractionated and characterized to investigate their inhibitory activity against angiotensin I-converting enzyme (ACE). The antihypertensive effect of egg white hydrolysates in strain SHR spontaneously hypertensive rats was also investigated. At optimal conditions, pH 8, 60°C, and (E)/(S) = 0.02%, digestion of 1% crude egg white solution by thermolysin was carried for 4 hours. The recovery yield from the supernatant after centrifugation was around 80%. The hydrolysate showed high ACE inhibitory activity (IC50 = 33 μg/mL) and imparted neither bitter taste nor the iron odor of egg whites. Sequential ultra-filtration of hydrolysate with MW cut-off 10,000, 3,000 and 1,000 Da resulted in increased activity from each filtrate up to IC50 = 17 μg /mL. Thermolysin was recycled from the hydrolysate for subsequent batch use for a total of four batches without reduction in anti-hypertensive activity. The hydrolysate demonstrated an anti-hypertensive activity in spontaneously hypertensive rats at an orally administrated dosage of 0.2 g/kg body weight.
Key words: angiotensin I-converting enzyme (ACE), antihypertensive activity, protein hydrolysate, egg whites.