Research On Oxidation Stability Of Polyunsaturated Oils Encapsulated By Octenyl Succinic Starch

Polyunsaturated oil, can reduce blood cholesterol and triglycerides, lower blood viscosity, anti atherosclerosis, regulate cardiac function, enhance the activity of brain cells, reduce the damage of stem cells and endothelial cell and enhance the body’s defense system. Therefore, polyunsaturated fats acids are deeply liked by consumers because of their health care function for human body. However, because of that polyunsaturated fatty acids have multiple unsaturated bond which lead to the more lively, when it is exposed to the air, there will soon occur automatically oxidation, free radicals, superoxide and chemical compounds such as aldehydes, ketones, and then lead to odor, color change, nutritional value reducing, and even produce toxic or harmful substances, induce lipid peroxidation or other diseases in vivo, consequently the antioxidant protection of polyunsaturated oil has become an important issue.Therefore, this study first explores different microcapsule wall when mixed with polyunsaturated oils on the peroxide value, and determine the DPPH free radical scavenging effect of microcapsule wall material, thus use the better wall materials to encapsulate the oil, filter out the best mixture ratio, determine the better emulsifying process parameters, observe the apparent morphology of microcapsule products using scanning electron microscopy, at the same time study the the molecular structure change of microcapsule wall materials using infrared spectrum method. Synchronous fluorescence spectrometry combined with infrared spectrometry were used to study the thermal protection of microcapsule wall on polyunsaturated fat, expecting to provide certain theoretical basis for production. The main research contents and conclusions are as follows:1. Arabia gum, hydrophobic starch (GRF), soy protein isolate, sodium caseinate, modified starch (93008) and maltodextrin can enhance the peroxide value of sunflower oil in varying degrees. Modified starch (93008) on the DPPH free radical scavenging effect was the best, the embedding rate of microcapsules respectively made by four wall material from high to low in turn for:modified starch 92032>Arabic gum>starch CO-01>sodium caseinate. Research the emulsification process with dosage of 8% sodium caseinate and 45% modified starch integrating multifarious effects.2. The surface oil content, leaching oil content and peroxide value of microencapsulated lipid of the microcapsules prepared by spray drying whose wall material and core material emulsified under the the condition of vacuum were slightly higher than that under the conditions of atmospheric pressure. The surface oil content of microcapsules which emulsified with tissue homogenate and colloid mill were significantly higher, high speed homogeneity emulsification was a better way. Oil droplet size decreases and the particle size becomes more uniform with the increase of homogenization pressure. The peroxide value of microencapsulated lipid produced by 45MPa homogenization pressure has been maintained at a relatively low level. Antioxidant addition does reduce the microencapsulated oil peroxide value, microencapsulation rate did not significantly improve compared to the previous which without any emulsifier the micro capsule. Micro encapsulation effect is the best which prepared under atmospheric pressure conditions, using a high pressure homogenizer, homogenization pressure of 45MPa, homogenizing for 3 times.3. Electron microscopy (SEM) observed that the majority of microcapsule are smooth, dense and crack free spherical particles. The particle size of the microcapsule that had been effectively embedded was about 24um and there are differences in particle size. The interaction of microcapsule wall material was analyzed by fourier transform infrared spectrum It was found that casein sodium and other wall happen effective association between molecules. Intermolecular hydrogen bonds formed between amino acid and the surrounding medium. Analysis of fitting results of casein acid sodium amide I band and casein sodium amide Ⅲ shown that, the content of a helices and β corner of protein secondary structure of sodium caseinate have increased, while the β fold and random coil content reduction, enhancing the flexible protein structure after spray drying. Analysis of the influence of heat treatment on oil by synchronous fluorescence spectrometry showed that the heat treatment destroyed the oil in the chlorophyll a, the longer the heating time, the greater the damage, and microencapsulation seems to be no significant thermal protection. The physical mixture of oil and wall material has obviously accelerated the thermal damage of oil, and then a new strong fluorescence peak occured at 390nm after heating, is likely to be other new-substances in the oil because of greater heat treatment. Infrared spectroscopy analysis of the influence of heat treatment on the oil found that crude oil without any treatment, crude oil after 30min heat treatment, crude oil with the heat treatment for 60s, microcapsule oil after 60s and oil extracted from the physical mixture with heat treatment for 60s had the same characteristic absorption peak, indicating that the the microencapsulation of oil and 60s heat treatment has little effect on the oil and basically maintained the original structure and nutritional value of oil. Infrared spectroscopy absorption peak appeared at 2360cm-1 and 2341cm-1 when the crude oil was heated for 30 min. The reason may be that the deeper heating degree which led to the oxidation and hydrolysis of oils and fats.4. Microcapsules prepared in this experiment is a milky white powder with a certain degree of mobility and pure taste, but no agglomerate phenomenon and peculiar smell. The content of surface oil and the embedding rate of microcapsule did not change significantly in the process of the accelerated oxidation experiment. The micro capsule oil acid value increased constantly with the extension of storage time, while the peroxide value increased from 0 to 8.42meq/kg, and then rose sharply to 521.31meq/kg on the 90th days. Changes in surface oil content of microcapsules stored at atroom temperature is small, and the acid value and peroxide value of microcapsule oil had increased rapidly and then decline quickly.