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.COPYRIGHT: (C)2015,JPO&INPIT【課題】茶葉あるいは茶殻を水乃至温水で抽出して得られる抽出残渣(茶殻)から調製方法が複雑でなく、食用として扱いやすく、優れた血圧降下作用が期待されるアンジオテンシン変換酵素阻害活性ペプチドを多く含有するタンパク質分解物を製造コストを抑えて製造し提供する。【解決手段】茶葉あるいは茶殻をアルカリ水溶液で抽出し、得られた抽出混合物をそのままタンパク質分解酵素で分解し酵素反応を停止した後に、酵素反応混合物をpH2から5にすることで未反応タンパク質を沈降させ、酸性水溶液可溶のペプチド画分と不溶性画分とを分離する工程を順次行う。また、タンパク質分解酵素での分解工程では、中性エンドペプチダーゼ、酸性エキソペプチダーゼを作用させる。さらにアルカリ抽出前後の工程で植物組織分解酵素を作用させてもよい。【選択図】なし
