The ACE inhibitory activity of a desalted protein hydrolysate from Northern shrimp (Pandalus borealis) was studied. Measurements by two independent methods both revealed higher in vitro ACE inhibitory activity, IC(50) = 0.075 and 0.035 mg/ml, respectively, than earlier reported in comparable hydrolysates. Two novel ACE inhibitory tri-peptides, Phe-Thr-Tyr (IC(50) = 275 and 59 mu M) and Phe-Ser-Tyr (IC(50) = 7.7 and 2.2 mu M), were detected in the hydrolysate. An introductory feeding trial with spontaneously hypertensive rats indicated positive in vivo results when the rats were given 60 mg hydrolysate/kg body weight per day. Although further in vivo studies are necessary to verify the antihypertensive potential, the very high in vitro ACE inhibitory activity reveals that the shrimp protein hydrolysate is a promising candidate for nutraceutical application. (C) 2011 Elsevier Ltd. All rights reserved.