Study On Walnut Protein And Polypeptide Prepared From Walnut Cake

In this study, walnut cake being used as the material, walnut protein was extracted through ultra-wave soaking. Hydrolysis was conducted to the extracted by biological approaches. Investigations were made into the processing technology for walnut protein extraction and the biochemical features of walnut polypeptide. Based on the findings, the technology for walnut polypeptide wine was probed. The findings are as follows:1. Use protein extraction rate as the index, adopt mono-factor and orthogonal tests, it is find that the optimal condition for walnut extraction is: ultral-wave soaking for 1 hour at 55℃with lye pH 8.5, the ration between the solution proportion is 1:20, the extraction rate could reach about 70%. When the pH of acid sedimentation is ranging from 4.0 to 5.0, the extraction rate could be up to 95%.2. Use hydrolysis index as the index,the enzymolysis capacity towards walnut protein is as follows: trypsin >neutrase >papain3. Use hydrolysis index as the index to investigate the enzymolysis technology of trypsin and neutral protease to walnut protein through quadric-regression orthogonal test. The result shows that: the optimal condition for trypsin enzymolysis is : to conduct enzymolysis for 4 hours with the substrate concentration at 2.7%, the total enzyme to be added is 8294.25u/g, the temperature for the experiment is at 53.41℃with pH8.0, the hydrolysis rate could reach 14.55%. the correlation regression model for the responding values and influencing factors is: Y=11.92055428-0.3487709405X₁+1.1967860007X₂+0.7774642839X₃-1.5849497678X₁²- 0.029698036129X₂²-0.20643118745X₃²-0.31250000000X₁X₂-0.06250000000X₁X₃- 0.06250000000 X₂X₃The result shows that: the optimal condition for neutrase enzymolysis is : to conduct enzymolysis for 4 hours with the substrate concentration at 2.93%, the total enzyme to be added is 4364u/g, the temperature for the experiment is at48.4℃with pH7.0, the hydrolysis rate could reach 13%. The correlation regression model for the responding values and influencing factors is: Y=8.63704427+0.6489851407X₁+1.0340564910X₂+0.17905664035X₃-0.6511419781X₁²+ 0.4976235055X₂²+0.09113725743X₃²-0.28750000000X₁X₂+0.11250000000X₁X₃- 0.3875000000X₂X₃4. Gel chromatography result indicates: in trypsin enzymolysis, polypeptide with molecular weight between 12000-5000 Da is about 12%; with molecular weight between 5000-1300 Da is about 18%; with molecular weight between 1300-600 Da is about 6%; with molecular weight between 600-300Da is about 6%; polypeptide with molecular weight lower that 300 Da and the amino acid is about 11%; In neutrase enzymolysis, polypeptide with molecular weight between 12000-5000 is about Da 6%; with molecular weight between 5000-1300 Da is about 24%; with molecular weight between 1300-600 Da is about 36%; with molecular weight between 600-300 Da is about 5%; polypeptide with molecular weight lower that 300 Da and the amino acid is about 6%.5. Walnut polypeptide has higher solubility and is almost free from pH variation. Meanwhile, it has the features of higher concentration, high reduction capability and lower viscidity. Compared with walnut protein, walnut polypeptide is much superior in emulsification, foam formation and oil absorption. It also has stronger resistance to oxidation and could promote fermentation and clear O₂^-., therefore it is ideal to be used for food processing.6. The investigation into polypeptide wine preparation indicates: the optimal fermentation temperature is at 24℃, the inoculation amount is 0.05% with pH4.0 for 6 days. In order to mitigate the bitterness of the wine, it is better to add 0.6%β-CD, 4% sucrose.