Study On Preparation And Antihypertensive Effect Of Peptide From Peanut Protein

Heat treated peanut meal is a good resource of vegetable protein,containing 40%-50%protein.Heat treated peanut meal as raw material for preparing antihypertensive peptides,could not only improve the added value of raw material,but also lay a foundation for the development of natural,safe and efficient functional food and enrich functional food market.Extraction peanut protein from heat treated meal was optimized by means of quadratic regression rotatable orthogonal design in this paper.Monitored by degree of hydrolysis(DH),the single protease hydrolysis process was optimized by uniform design method.Based on the results of single protease hydrolysis,the factors affected hydrolyzing peanut protein by compound protease combined with physicochemical pretreatment were studied,and the angiotensin converting enzyme inhibitory effect of crude peptides was detected.And then,membrane separation technology was used to separate and purify the crude peptides.Spontaneously hypertensive rats(SHR)were selected to test antihypertensive activity of refined peptide in vivo.The experimental results were as follows:1.Alkaline-extraction and acid-precipitation were employed to isolate peanut protein from heat treated peanut meal.The results of quadratic regression rotatable orthogonal design showed the optimum conditions of isolation were as follows:the alkaline-extraction was at 60℃,pH9.5 for 120 min with the ration of solid to water at 1:8(m/v).Under these optimal conditions,the extraction rate of peanut protein was 64.2%,and the purity of peanut protein was 83.14%.2.Optimum conditions of single protease hydrolysis:the alcalase hydrolyzed peanut protein under the conditions of hydrolysis time 369.07 min,substrate concentration 1.00%,E/S 7039.49 U/g,the DH was 30.57%.Pepsin hydrolyzed peanut protein under the conditions of hydrolysis time 386.25 min,substrate concentration 1.09%,E/S 7429.79 U/g,the DH was 27.85%.Bromelain hydrolyzed peanut protein under the conditions of hydrolysis time 382.68 min,substrate concentration 1.07%,E/S 7642.50 U/g,the DH was 23.40%.3.The results of compound proteases combined with physicochemical pretreatment:added 0.07%Na2SO3 to 5%peanut protein solution at 45℃,and kept striing for 1h.Alcalsae hydrolyzed the pretreated peanut protein solution under the condtions of pH8.0,temperature 50℃,E/S 7039.49 U/g for 120 min.Adjusted temperture to 45℃ pH to 6.8,bromelain was added with E/S 7642.50U/g,hydrelysis time 120min.DH was 19.08±0.17%,the concentration of short peptide was 17.67±3.09 mg/mL,the yield of short peptide was 40.76±3.41%,the IC50 value of angiotensin converting enzyme inhibitory effect was 8.68 mg/mL,the ORAC value was 1825.22±62.29 μmoL Trolox/g dried.4.The IC50 of permeate which produced by ultrafiltration with 1 kDa membrane was 0.88 mg/mL,the ORAC value was 2232.89±88.89 μmoL Trolox/g dried.The optimum conditions of constant volume ultrafiltraton were temperature 45℃,pressure 0.193 MPa,the amount of added water 3 times,the premeability of short peptides was 65.01%.And molecular weight of short peptides in permeate mainly distributed between 284 Da and 401 Da,below 1 kDa.The optimum times of added water was 10 in interval and constant volume nanofiltration operation.The rate of desalination was 58.67±1.50%,removal rate of Na+was 69.78±0.69%,the loss precent of short peptides was 2.00%.The IC50 of desalinated freeze-dried powder was 0.78 mg/mL,the ORAC value was 2359.50±40.43μmoL Trolox/g dried.5.The results of SHRs experiment showed that systolic blood pressure(SBP)significantly reduced at oral administration dosage of 1000-1500 mg/kg body weight.And at oral administration dosage of 1500 mg/kg body weight,the SBP decreased to 16-25 mmHg after administration,the effect could last 8 h.