| Summary: | 碩士 === 國立中央大學 === 化學工程與材料工程學系 === 107 === 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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