| Walnuts are one of the oldest tree nut of the world. China is the first cultivated area of walnut tree and the second yield of walnut country in nowadays, which produce approximately more than 200,000t walnut every year. With the Strategy of Developing the West Region, the yield of walnut and the cultivated area of walnut tree will increase quickly in the near future. Therefore, it is necessary to study on the walnut processing technology.Walnut kernels generally contain about 60% of oil. The major fatty acids found in walnut oil are oleic (C18:l), linoleic (C18:2) and linolenic (C18:3) acids. Walnut fat is mostly unsaturated, and unsaturated fatty acids have been associated with beneficial effects on serum lipids. Compared with other nuts, a unique aspect of walnuts is that they are a rich source of both omega-6 (ω-6) and omega-3 (ω - 3) polyunsaturated fatty acids (PUFA), which are essential dietary fatty acids. Epidemiological and clinical trials suggest that frequent walnut consumption is associated with a decrease in coronary heart disease (CHD). Furthermore, walnut are a rich source of vitamin E , fiber, magnesium, potassium, and arginine. So the walnut is believed to be healthy food for a long history. The walnut oil, as a kind of functional edible oil, becomes mor; and more popular in the developed country.On the other hand, the walnut oil is relatively unstable compared to other common plant oils, which can be ascribed to its high content of PUFA. It is important to prevent the walnut oil from oxidation during the process and storage period. Vitamin E is a natural antioxidant as well as has important physiological effects. Microencapsulation is a new Hi-Tech, which the oil can be protected by the wall materials encapsulation effect. So we expect to microencapsulate the walnut oil with VE and improve its oxidative stability.Specific objectives of the study were 1) investigate effect of different extraction methods on walnut oil quantity and quality. 2) analyze fatty acids profile of walnut oils with different extraction means by GC and VE profile by RP-HPLC.3) investigate stabilities of 3 walnut oil by Rancimat apparatus.4) microencapsulate the walnut oil with VE and produce fat powders. These data may help we select proper extractiontechnology for walnut oil and keep its quality. The results of the experiments are listed as follow.1 In comparison with 3 ways of extraction, the production of walnut oil is putted in order: solvent extraction >SCF-CO2 extraction>screw press extraction. The oil cake contains high content of residue oil(16.5%) and richs in crude protein, which is a good source of protein and should be utilized.2 Extracting walnut oil with SCF-CO2 is a new kind of advanced technology. Compared with two other means, the obtained oil has the following several traits: the light color, the low acid value, the low sponification value, the low peroxide value and so on . The quality of this oil is obviously superior to the other two kinds of oils.3 The parameters of extracting walnut oil with SCF-CO2 is the following: the press,30Mpa; the temperature,35 ℃; the extraction time ,3.5h; the rate of CO2 flow, 15-20kg/h;The cosolvent is free-water C2H5OH and the employing quantity is 10 % of the overall used raw material.4 The 3 different ways have not obvious effect on the fatty acid profile of walnut oil .The results of the experiment indicate that the major fatty acids in walnut oil are palmitic(C16:0),stearic(C18:0),oleic(C18:l),linoleic(C18:2),linolenic(C18:3) acids. In which, USFA account for more than 90% of the total fatty acids, and especially PUFA account for more than 75 % of the total fatty acids.5 The content of tocopherol in walnut oil obtained from the 3 ways is sequenced: solvent extraction > screw press extraction > SCF-CO2 extraction. The Y -VE is predominant VE in the VE profile of walnut oil.6 The content of phosphatide in walnut oil obtained from the 3 ways is sequenced: solvent extraction > screw press extraction > SCF-C02 extraction. The stabiliti...
|
PDF Full Text Request