Production and characterization of angiotensin converting enzyme (ACE) inhibitory peptides from apricot (Prunus armeniaca L.) kernel protein hydrolysate

Six different proteases (Flavourzyme®, Neutrase®, Protamex®, Alcalase® 2.4L, Proleather® FG-F, and papain) were employed to hydrolyze apricot kernel protein (AKP). Alcalase® is an inexpensive and non-specific protease that has been shown to be useful for the generation of bioactive peptides from AKP. Alcalase® 2.4L was selected for further study on enzymatic preparation of ACE inhibitory peptide from AKP. After 60-min hydrolysis, the highest ACE inhibition was 82 ± 0.14%. Results of molecular weight distribution revealed that most of ACE inhibition activity was probably attributed to low-molecular weight peptide fraction ranging from 200 to 900 Da. Ultrafiltration on membranes with several molecular weight cutoffs (MWCFs) demonstrated that most of the ACE inhibitory activity was due to peptides with a less than 1,000 Da molecular weight: the IC₅₀ value of the 1-kDa ultrafiltrate was 0.15 ± 0.007 mg mL⁻¹, while it was 0.378 ± 0.015 mg mL⁻¹ before ultrafiltration. Additionally, further separation and purification of the ACE inhibitory peptides were carried out using gel filtration and C₁₈ RP-HPLC. The result of research can be used to optimize AKP enzymatic hydrolysis for producing ACE inhibitory peptides which could be used for food industry and nutraceuticals.