Extraction Of Unsaturated Fatty Acids From Silkworm Pupa Oil And Preparation Of Its Microcapsules

Silkworm pupa as the reeling industry by-product is often dumped or used as fodder for animals, which is mainly made up of fat, protein and chitin. The fat accounts for18%-30%only fewer than the content of silkworm protein. Silkworm pupa fat is rich of unsaturated fatty acid glyceride, and after completely hydrolysis unsaturated fatty acids accounts for66.8%-72.0%, which is mainly alpha-linolenic acid. Alpha-linolenic acid is edible long-chain omega-3polyunsaturated fatty acids, which is the essential fatty acid for body’s synthesis of DHA and EPA. In this paper, Silkworm pupa crude oil was used as raw materials to make silkworm pupa unsaturated fatty acids. The main research methods are pre-treatment of silkworm pupa crude oil, saponification under normal pressure to make mixed fatty acids, solvent method at low temperature to separate unsaturated fatty acids from saturated fatty acids. In order to enhance the oxidation resistance ability of unsaturated fatty acids, microencapsulating process was studied. Finally storage stability and release ability in simulated gastrointestinal fluid of microcapsules were tested by experiments.The main research results were as follows:(1)With crude silkworm pupa oil as raw material, saponification under normal pressure, solvent method at low temperature were used to prepare high purity unsaturated fatty acids. First, response surface methodology(RSM) was used to optimize conditions for saponification process, the optimum saponification conditions at the constant alkali mass fraction15%, extra alkali content44.81%(w/w), saponification time3.28h, saponification temperature97.87℃; Second, high purity unsaturated fatty acids was obtained by solvent method at-10℃, the conditions were mass ratio of solid to solvent1:2.4(w/w), methanol mass fraction90%(w/w), time30min at-10℃; Finally, after bleaching with activated clay its chemical and physical characteristics were determined and oxidative stability were studied. This process has the following characteristics: saponification with sodium hydroxide solution saves a lot organic solvent which was used to produce mixed fatty acids, reducing the risk of operation. Solvent method at low temperature to separate unsaturated fatty acids from saturated fatty acids has a short-time, high-yield, labor-saving advantages of mass production for industrial production. Physical and chemical properties of products are as follows:95.96%unsaturated fatty acids, acid200.23mgKOH/g, iodine value170gI2/100g, peroxide value1.62mmol/kg.(2)Encapsulation of silkworm pupa unsaturated fatty acids with chitosan and lactose as the main wall material was carried out by a spray-drying process. Response Surface Methodology (RSM) was used to study and optimize technological parameters of the ratio of lecithin, ratio of lactose and chitosan and ratio of core and wall materials. The optimal condition was determined as follows: the ratio of lecithin to chitosan is13%(w/w), ratio of lactose to chitosan is1.42:1.0(w/w) and ratio of core/wall is0.52:1.0(w/w), at which the microencapsulation efficiency (MEE)83.31%, surface oil efficiency13.76%and microencapsulation yield97.74%. The encapsulated silkworm pupa unsaturated fatty acids produced by this method has good dispersibility and the microcapsules with an average diameter of about4μm were smooth and spherical morphology, product appearance is milky white powder with good fluidity.(3)Oxidative stability and shelf life of silkworm puma unsaturated fatty acid and microcapsules were studied. The best storage conditions for unsaturated fatty acid were no exposure to light and air, with200mg kg-1of TBHQ stored at4℃. For microcapsules, core oil during storage due to the wall material protection, peroxide value changes unaffected by the impact of environmental factors, what resulting in a higher form of oil peroxide value is presumably instantaneous high temperature caused by the spray drying process. Determined by oven experiments shelf-life can be extended from4months to8months. Compared to products without any protections, silkworm puma oil fatty acids shelf life was greatly extended.(4)The release ability was studied and microcapsules were subjected to an in vitro gastrointestinal fluid. Result shows that the cumulative releasing rate in vitro gastric fluid for4.0h was only50%, so the microcapsule wall material played sustained-release property, but in vitro intestinal fluid for1.0hours cumulative releasing rate reached70%.Presumably, microcapsules showed rapid-release property in gastric juice model and sustained-release property in intestinal fluid.