| 摘要 |
PROBLEM TO BE SOLVED: To provide a simple, low cost method for preparing protein digests from tea leaves or extraction residues after extracting tea leaves with water or warm water (used tea leaves), where the protein digests are easily applicable for food, and rich in peptides that inhibit angiotensin converting enzyme so that an excellent blood pressure-lowering effect is expected.SOLUTION: The method of the invention comprises the steps of: extracting tea leaves or used tea leaves with an alkali aqueous solution; digesting the obtained extraction mixture by using a protease; lowering pH of the enzyme reaction mixture from pH2 to pH5 after stopping the enzyme reaction to precipitate undigested protein to separate the peptide fraction soluble in an acidic aqueous solution from the insoluble fraction. In the digestion step, the protease may be neutral endopeptidase and acid exopeptidase. Further, a vegetable tissue degrading enzyme may be reacted with the tea leaves in the steps before or after the alkaline extraction step. |
