Research On Enzymatic Preparation And Properties Of Rapeseed Peptides

Rapeseed as the second significant oilseed, is widely planted. The production of rapeseed in China plays an important role, and the planting area and output rank first in the world. Rapeseed is not only a source of edible vegetable oil, but the rapeseed meal, also a good vegetable protein resources. In this dissertation, rapeseed meal as the raw material was directly hydrolysed by adding proteases to produce peptide. The results are shown as follows:The neutral protease, alkaline protease, papain and composite botanic proteolytic enzyme were conducted under their appropriate enzymatic hydrolysis conditions. The results indicated that the effect of neutral protease hydrolysis is best, then followed by alkaline protease, at last is composite botanic proteolytic enzyme and papain. Through the comparison of different hydrolysis styles with neutral protease and alkaline protease, hydrolysis simultaneous was more conducive to improve the yield of peptides.The relationship between the peptides yield and enzymatic hydrolysis condition,such as enzyme dosage, enzyme ratio, the ratio of material to water, hydrolysis time, was studied. Finally, the condition that the mixed proteases hydrolyse rapeseed meal was optimized by the response surface methodology. The results showed that the optimition hydrolysis condition was the enzyme dosage4500U/g, hydrolysis temperature50℃, pH8.0, the ratio of material to water1:8, the ratio of alkaline protease to neutral protease3:1, hydrolysis time6.5h; in this condition, the peptides yield was about54.89%.Ultrafiltration, active carbon and Sephadex G-25were used for the separation and purification of rapeseed peptides. The membrane permeability of peptides was about85.46%with a MWCO of100,000Da ultrafiltration membrane to deal with the hydrolyzate. The decolorization rate of hydrolyzate was about48.15%and the loss rate of peptides was5.47%after using active carbon. Then the hydrolyzate was further purified by GFC. The GFC results showed that The respective proportions of the three peaks were5.34%,41.67%, 52.99%, and the composition of peak II (molecular weight from500Da to8000Da) were peptides.The properties of peptides were investigated. The results indicated that the viscosity of rapeseed peptides was low; the solubility was good; compared with the rapeseed protein, rapeseed peptides had a better oil-absorbing capacity; the reducing power of rapeseed peptides and concentration showed a good dose-effect relationship; the scavenging effects on O2-·of rapeseed peptides had a strong concentration-dependent, and its IC50was2.58mg/mL; the rapeseed peptides exhibited a certain extent ACE inhibitory activities, and its IC50was7.48mg/mL. In all, this is good for the further application of peptide powder.