Study On Hydrolyzed By Enzmye Preparation And Antioxidative Activities Of Rapeseed Peptide

Rapeseeds have rich nutritional value, in addition to being an important rawmaterial of edible oil, they are ideal human protein resources. This thesis hasdetermined the optimal process for preparation of rapeseed protein peptide byenzymolysis method.4groups of rapeseed peptide by different molecular weight weregotten by Ultrafiltration. And we also have studied their vitro antioxidant activity.There are four aspects in the main study contents:1. Optimize the conditions of theenzymatic hydrolysis of rapeseed protein peptide and create a mathematical model ofthe influence to the hydrolysis degree of rapeseed protein peptide by single factor.2.Study the processing characteristics of rapeseed protein peptide.3. Separate andpurify rapeseed protein peptide, then study the conformation of them.4. Evaluate theantioxidant activity of rapeseed protein peptide. The results are as follows:1. The degree of hydrolysis (DH) of rapeseed protein and the peptide yield as theevaluation indexes, this experiment preliminary studied the related conditions of theenzymolysis of rapeseed protein by Alcalase alkaline protease. And rapeseed proteinhydrolysis degree (DH) as response value, the study optimized the enzymolysisconditions of rapeseed protein by response surface methodology. By single factorexperiments, determined that enzymolysis pH, the amount of enzyme and substrateconcentration have significant influence on the degree of hydrolysis (DH). On thisbasis, according to the Box-Benhnken central composite experimental designprinciples, used3factors and3levels of response surface for analysis. Then analyzedand compared the experimental results, establish a mathematical model of theinfluence to the hydrolysis degree of rapeseed protein peptide by single factor. Andultimately determined the best conditions for rapeseed protein enzymolysis: pH of8.45, temperature of55°C, the enzyme dosage of5000U/g protein, the substrateconcentration of4.49%, and the reaction time of180min. Under the optimizedconditions, the hydrolysis (DH) degree of rapeseed protein theoretically could up to15.00%, the experimental degree of hydrolysis (DH) actually up to14.71%, the yieldof rapeseed peptide was73.02%, and the enzymolysis by Alcalase was the best.2. The experiment has comparatively studied the processing features of rapeseedpeptide and rapeseed protein, in order to provide relevant theoretical basis to itsapplication in food industry. The experimental results show that: On one hand, the water absorption and solubility of rapeseed protein peptide significantly improvedcompared to the rapeseed protein.When pH=7, rapeseed protein peptide waterimbibition is3.2mL/g, n nearly1.5times of rapeseed protein. and its oil absorption,emulsifying, foaming and foam stability were all better than that of rapeseed protein.So we can consider adding rapeseed protein peptide to whipped foam foods, such ascake, ice cream, jam. On the other hand, there was a larger gap between emulsionstability of rapeseed protein peptide and rapeseed protein. When pH7, rapeseedprotein emulsification is45.69%, higher than the42.73%of rapeseedpeptides,Therefore, in the process of processing applications, we should circumventthis processing characteristic.3. Classified rapeseed polypeptide enzymolysis liquid according to the molecularweight by using Ultrafiltration membrane separation technology. The results showedthat in the peptide mixture, rapeseed peptides with the smaller molecular weight of1,000or less were the most, and the content was46.53%(by mass). By analyzing theamino acid composition of various components of crude rapeseed peptide andrapeseed peptide after separation and purification, we found that hydrophobic aminoacid content of RPH1increased to33.26%after the rapeseed peptides beingultrafiltrated. It improved2.15%compared with the hydrophobic amino acid contentof RPH of crude rapeseed peptide.4. Studied the antioxidant activity of the rapeseed peptides after ultrafiltration.Determined the antioxidant activity of five groups of rapeseed protein peptides withdifferent components by five experimental methods: rscavenging DPPH radicalactivity, rscavenging superoxide anion radicals, chelating metal ions ability,inhibition of lipid peroxidation and determining iron reduction ability. The resultsshowed that: The rapeseed peptide with below1kD molecular weight exhibited strongantioxidant activity.The experimental results show that: RPH1（<1kD）in thecrscavenging DPPH radical activity, rscavenging superoxide anion radicals,anddetermining iron reduction ability had the strongest oxidation resistance. And inchelating metal ions ability, rapeseed peptides component RPH4(5-10kD) had thestrongest ability.