Preparation Of Pumpkin Seed Oil Pickering Emulsion And Its Stability And Digestion Characteristics

Pumpkin seed oil has many benefits to human health,such as anti-inflammatory,lowering blood pressure,preventing prostate disease and cancer.However,because it contains more oleic acid and linoleic acid,has a high degree of unsaturation,is prone to oxidation and deterioration,and has the disadvantages of low direct oral utilization and poor water solubility,which limits the application of pumpkin seed oil in food.Pickering lotion can be formed without traditional emulsifiers,avoiding the toxicity caused by some surfactants,and the solid particles used to prepare Pickering lotion have irreversible adsorption at the oil-water interface,so it has strong stability..In this study,pumpkin seed protein rosmarinic acid complex was prepared by alkali method,and used as an emulsifier to stabilize pumpkin seed oil Pickering emulsion.The effect of Pickering emulsion on the storage stability of pumpkin seed oil was further explored.Finally,the digestion characteristics of pumpkin seed oil Pickering emulsion and the activity of improving the prostatic hyperplasia were studied.The main research results of this paper are as follows:1.Preparation and characterization of pumpkin seed protein rosmarinic acid complex.The structure of the composite was characterized by Malvin laser particle sizer,Fourier infrared spectroscopy and scanning electron microscope,and its storage stability was explored.The results showed that the particle size of pumpkin seed protein nanoparticles(PSP)was about 79.4 nm,the PDI was 0.267 and the Zeta potential was-33.0 m V;The particle size of pumpkin seed protein rosmarinic acid complex(PSP-RA)was about127.5nm,PDI was 0.284 and Zeta potential was-38.6 m V.They have good dispersion and stability.There is hydrogen bond interaction between PSP and RA,which not only changes the secondary structure of the protein,but also changes the surface structure of the protein.PSP and PSP-RA have favorable stability when stored at 4℃ for two weeks.2.Preparation and basic properties of pumpkin seed oil Pickering emulsion.PSP and PSP-RA were used as emulsifiers to stabilize pumpkin seed oil Pickering emulsion,and characterized by laser particle size analyzer,laser scanning confocal microscope and rheometer.The results showed that when the volume fraction of oil phase was 70%,the Zeta potential of pumpkin seed oil Pickering emulsion reached-28.0 m V and-40.2 m V,and the system was very stable at this time.Pumpkin seed oil Pickering emulsion is oil in water emulsion,and PSP stabilized emulsion has better viscoelasticity.Under the condition of 0～100mmol/L salt concentration,pumpkin seed oil Pickering emulsion has favorable stability.Under the condition of 85℃,the emulsion of PSP stabilized appeared demulsification,and the emulsion stabilized by PSP-RA showed more excellent thermal stability.3.Effect of Pickering emulsion system on pumpkin seed oil storage stability.The changes of oxidation index and active substance content in pumpkin seed oil Pickering emulsion at room temperature and 37℃ storage were investigated.The results showed that the acid value,peroxide value and TBA value of Pickering emulsion system were significantly lower than those of pumpkin seed oil at 37℃ for 30 d.In addition,the contents of total phenols,total tocopherols,total sterols,squalene and unsaturated fatty acids in the Pickering emulsion system decreased by 26.76%,28.95%,12.72%,22.6%,0.97%,respectively.Compared with pumpkin seed oil,the decrease rate of active substance content(40.25%,44.04%,17.51%,37.2%,2.83%)was significantly lower.The results showed that Pickering emulsion system could inhibit oxidative rancidity of pumpkin seed oil and reduce the loss of active substances.4.Study on the digestive characteristics of pumpkin seed oil Pickering emulsion and the improvement of the activity of BPH.Through the simulated digestion experiment in vitro and the establishment of benign prostatic hyperplasia(BPH)rat model to explore it.The results showed that after 2 h digestion,a few drops of oil were still unhydrolyzed in the Pickering emulsion of pumpkin seed oil,and the release rate of free fatty acids was close to 90%.This indicated that the emulsion could be hydrolyzed well in the digestion phase of the small intestine.The inhibition rate of pumpkin seed oil Pickering emulsion on the prostate wet weight and index of BPH rats was 66% and 65.9% respectively.The image of prostate tissue structure showed that the proliferation degree of the pumpkin seed oil was greatly improved,which was close to the normal gland.Meanwhile,the inhibition rate of pumpkin seed oil on the weight and index of prostate in BPH rats was only 52.3% and50.6% respectively.The results of acid phosphatase activity and serum sex hormone level also showed that pumpkin seed oil Pickering emulsion had a better effect on BPH than pumpkin seed oil.