Pilot-Scale Process Of Aqueous Enzymatic Extraction Of Peanut Oil And Protein Hydrolysates And Study On Peanut ACE Inhibitory Peptides

Peanut is one of the most important oilseeds in the world. The oil content of peanut is about 50% and the protein content is 24% to 36%. Conventional industrial oil processing involves mechanical pressing and solvent extraction. Mechanical pressing is labor intensive and energy consuming, while solvent extraction has some problems of production security and edible safety, and the protein would not be used completely. The laboratory technique of aqueous enzymatic extraction of peanut oil and protein hydralysates has matured. In order to apply the technique into industrial production, pilot-scale process of aqueous enzymatic extraction of peanut oil and protein hydrolysates was carried out based on the previous results in this dissertation. The mechanism of aqueous enzymatic extraction of oil and the peanut protein hydrolysates obtained from pilot-scale process were studied. The results are as follows:First the pilot-scale process of aqueous enzymatic extraction of peanut oil and protein hydrolysates was carried out and two processes were compared. The three-phase separator was chosen to separate oil, oil-water mixture and insoluble residue simultaneously in pilot-scale process 1. Then oil-water mixture was treated by the disk separator to obtain free oil, emulsion and hydrolysate solution. After spray drying, peanut protein hydrolysates powder was obtained from hydrolysate solution. As a result, total free oil and protein hydrolysates yields were 73.77% and 55.10% respectively. In pilot-scale process 2, only three-phase separator was used. The free oil yields were 79.68% (with hull) and 81.95% (dehulled), while protein hydrolysates yields were 73.05% (with hull) and 72.20% (dehulled). The yields have achieved to the level of laboratory technique. The color, peroxide value, acid value and other qualities of peanut oil from pilot-scale processes reached the national standard of third class peanut oil, so the peanut oil obtained from aqueous enzymatic extraction process can be edible after simple refining.The peanut cells and emulsion at different enzymatic time were observed by SEM and TEM. The circular dichroism and surface hydrophobicity of protein on the emulsion interface and in aqueous phase were measured to learn the mechanism of aqueous enzymatic extraction of peanut oil and protein hydrolysates. After dry grinding, most cell content came out into the solution during alkaline extraction process, then the protein was hydrolyzed by protease and oil was released. At the same time, protein on the emulsion interface was also degraded by protease. As a result, its secondary structure has obviously changed, protein film on the interface broke, and the emulsion was demulsified. Thus, free oil and protein hydrolysates yields were greatly improved.The macroporous adsorption resins (type: DA201-C) were used to treat the peanut protein hydrolysates to remove salt. The results of dynamic adsorption and desorption show that 50mg/mL peanut protein hydrolysates were adsorbed onto mcroporous at 60mL/h rate. Then the chromatographic column was washed with deionized water. When the conductivity of the eluent decreased until it was the same with deionized water, desorption was carried out with 75% ethanol. After the eluent was collected, evaporated and freeze-dried, we got crude peanut peptides, the protein content of which reached about 80% and the desalination ratio is 91.02%. Both peanut protein hydrolysates and desalted peanut peptides were made reducing power, scavenging abilities on free radicals including DPPH·,·OH and O2—·testing and ACE inhibitory activity testing. The results shown that desalted peanut peptides has stronger antioxidant activity and ACE inhibitory activity than peanut protein hydrolysates.Peanut peptides were separated and purified by Sephadex G-15, semi-preparative reverse-phase high performance liquid chromatography (RP-HPLC) and analytical RP-HPLC. After these, two active fraction G3-R2-r3 and G3-R4-r2 were obtained, which were tested to have better ACE inhibitory activities. The amino acids sequences of these peptides were gained using MALDI-TOF-TOF tandem mass spectrometry, which were Tyr-Thr-Thr-Pro-Thr(YT-5), Tyr-Thr-Thr-Pro-Val-Thr(YT-6), Arg-Arg-Met-Leu-Tyr(RY-5) and Pro-Gly-Arg-Val-Tyr(PY-5).We synthesized the four peanut ACE inhibitory peptides according to the sequences. Then G3 which was separated by Sephadex-15 and the peanut ACE inhibitory peptide which has the highest ACE inhibitory activity were chosen to test the effects on blood pressure in spontaneously hypertensive rats (SHR). And it's proved that peanut ACE inhibitory peptides can control blood pressure effectively in SHR.