| Rapeseed peptides are small molecule chain peptides with certain bioactivities, prepared after hydrolysis of rapeseed protein. The research of rapeseed peptides is an important direction of process in depth and utilization of rapeseed meal, a byproduct of oil industry. The double-low rapeseed meal was used as raw materials in this paper to prepare two protein isolates through alkaline extraction and acid precipitation method. By comparison of their chemical composition and functionality, the rapeseed protein RP5.8with a higher yield and good functionality was chose as material for the follow-up enzymatic test. The rapeseed peptides were prepared from rapeseed protein RP5.8through controllable enzymatic hydrolysis technology, optimization of pretreatment and hydrolysis conditions using the degree of hydrolysis as an indicator. Rapeseed peptides with different molecular weights were obtained after crude separation of the hydroly sates through ultrafiltration membranes and their anti-alcoholism bioactivities in vitro and animal tests were investigated. The main findings were as follows:Two rapeseed proteins, RP5.8and RP3.6, were prepared from double-low rapeseed meal with the yield of12.26%and7.74%respectively, and crude protein content of70.66%and85.74%respectively. The moisture contents in the two proteins were10.67%and6.89%respectively, and ash content1.97%and5.12%respectively.Amino acid composition in the two protein isolates was determined and the results indicated that the two isolates are rich in essential amino acids. The amount of essential amino acids in rapeseed protein RP5.8accounted for38.5%of the total amino acids. Their amino acid patterns matched better with that recommended for children by the FAO/WHO, suggesting that the two proteins could be applied to children’s food.By comparing the solubility and other functional properties of the two rapeseed proteins, rapeseed protein RP5.8had better solubility and rheological behavior and was thus used for subsequent enzymatic test, while rapeseed protein RP3.6had better water holding, oil absorption and emulsification capacities and could be used as an additive in meat and an emulsifier in cake.Pretreatment of rapeseed protein before hydrolysis indicated that ultrasound had higher degree of hydrolysis and simpler operation among the four treatments-heat, ultrasound, tripolyphosphate and succinyl anhydride. The hydrolysis degree was10.49±0.22%under500W power of ultrasonic treatment at50℃for30min,.The hydrolysis process was optimized using response surface method on the basis of single factor test and the optimal conditions were as follows:pH7.7, alkaline protease dosage to protein11.6%, temperature52℃. The actual measurement of the rapeseed protein hydrolysis degree was12.29%under the optimal conditions.Three rapeseed peptide components, RPU-Ⅰ (>5kDa), RPU-Ⅱ (1-5kDa) and RPU-III (<1kDa), were obtained by ultrafiltration to the protein hydrolysates with their yield30.72%,24.13%and0.5%respectively.Hydroxyl radical scavenging capacity of RPU-I was highest with its value56.46%among RPU-Ⅰ, RPU-Ⅱ, RPU-Ⅲ and enzymatic hydrolysates before ultrafiltration. The laboratory mice in animal tests fed with sample RPU-I and RPU-Ⅱ in a dosage of0.17g per mice and0.1g per mice respectively had no drunken, indicating that sample RPU-I and RPU-II have function in improving tolerance of body to alcohol. The latency and hangover time in drunken mice fed with enzymatic hydrolysates were significantly longer than those in the control model group, with20.0±1.4min and180±7.1min respectively. In short, the rapeseed protein hydrolysate, sample RPU-I and RPU-II, had significant function of hangover. |
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