米為台灣人最大宗的主食之一，在稻米的加工製造過程中會把稻米中的澱粉提取出來用於後續的釀酒或發酵作業上，而去除澱粉的米渣就成了其加工產業中最主要的農業廢棄物。米渣通常會乾燥後當作動物飼料來處理，米渣中含有豐富的營養物質，但其工業附加價值低。因此本研究利用米渣中含有豐富蛋白質的特性，利用不同的酵素在最適反應環境下水解米蛋白，並尋找米蛋白水解液對抗氧化及抗高血壓能力的最適化水解條件。
本實驗利用米蛋白酶會溶於鹼性液體的特性將米蛋白從米渣中初步純化，並探討不同pH沈澱物對米蛋白水解物的影響，發現pH=5時析出的蛋白質，經過Alcalase水解後有最大的蛋白質利用率及胜肽濃度。接著利用三種酵素(Alcalase、Flavourzyme、Trypsin)以單一酵素和兩階段酵素進行水解並探討其DPPH自由基清除率和鐵離子螯合率等抗氧化活性。實驗發現Alcalase水解產物有較大的抗氧化活性，且在水解2小時後達到最大值，而Flavourzyme水解產物之抗氧化活性僅次於Alcalase水解產物，故第二階段利用Alcalase和Flavourzyme混合水解的方式探討是否能提升抗氧化活性。實驗結果發現在Alcalase水解2小時後再加入Flavourzyme水解6小時有最大的自由基移除率及鐵離子螯合率，分別為68.9 %及68.9 %。接著將水解液分成> 10 kDa、10-3 kDa及< 3 kDa三種不同的分子量區間進行抗氧化實驗，發現10-3 kDa的分子量區間有最好的抗氧化效果。利用上述水解條件得到的米蛋白水解液進行抗高血壓的測定，可以發現單一酵素水解中，Alcalase水解產物比Flavourzyme水解產物有較好的ACE抑制活性，且兩階段酵素水解並不能得到較好的結果，推測是加入第二種酵素後會使胜肽的結構產生改變，導致ACE抑制活性下降。但若將水解液分成不同大小的分子量區間進行測試，可以發先小分子量有較好的ACE抑制效果。

Rice is a principal food source for Taiwanese. In the processing and manufacturing process of rice, the starch in rice is extracted for subsequent brewing or fermentation, and the starch removed residue is the most in the processing industry which is the main agricultural waste. Rice dreg is usually dried and treated as animal feed. The rice dreg is rich in nutrients, but its industrial added value is low. Therefore, this study utilizes the characteristics of protein rich in rice dreg, uses different enzymes to hydrolyze rice protein in the optimum reaction environment, and searches for optimal hydrolysis conditions for rice protein hydrolysate against oxidation and antihypertensive ability.
In this experiment, rice protein was initially purified from rice dreg by using the characteristics of rice protease dissolved in alkaline liquid, and the effects of different pH precipitates on rice protein hydrolysate were investigated. It was found that the protein precipitated at pH=5 had the maximum protein utilization and peptide concentration after Alcalase hydrolysis. Then, three enzymes (Alcalase, Flavourzyme, Trypsin) were used to hydrolyze with a single enzyme and two-stage enzymes to investigate the antioxidant activities such as DPPH free radical scavenging rate and iron ion chelation rate. It was found that Alcalase hydrolysate has a large antioxidant activity and reaches a maximum after 2 hours of hydrolysis. The antioxidant activity of Flavourzyme hydrolysate is second only to Alcalase hydrolysate. Therefore, the second stage uses Alcalase and Flavourzyme to study whether it can enhance antioxidant activity.
The experimental results showed that the maximum of free radical removal rate and iron ion chelation rate were obtained after the hydrolysis of Alcalase for 2 hours and the addition of Flavourzyme for 6 hours. The free radical removal rate and the iron ion chelation rate were 68.9 % and 68.9 %, respectively. The hydrolysis solution was then divided into three different molecular weight ranges of > 10 kDa、10-3 kDa and < 3 kDa for antioxidant experiments. It was found that the molecular weight range of 10-3 kDa had the best antioxidant effect.
The determination of antihypertensive using the rice protein hydrolyzate obtained by the above hydrolysis conditions can found that Alcalase has good ACE inhibitory activity than Flavourzyme, and the mixing of the two enzymes does not give the good results. It is speculated that the addition of the second enzyme will result in a change in the structure of the peptide, resulting in a decrease in ACE inhibitory activity. However, if the hydrolysate is divided into molecular weight ranges of different sizes for testing, a small molecular weight can be obtained with a good ACE inhibition effect.

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