| Fish oil is a rich source of n-3 polyunsaturated fatty acids, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which have functions as preventing heart and blood vessel diseases, nourishing the brain, enhancing immunity the ability of resisting infection and anti-cancer function. EPA and DHA in oils are highly unsaturated and are therefore highly susceptible to oxidation in the presence of air, light and high temperatures. Oxidative lipids lose physiological functions and nutritive value. Fish oil oxidation can be reduced by microencapsulation of the oil, which could resist the oxidation, conceal fishy smell, stabiliz the core material and keep its function. Furthermore, microencapsulation of fish oil expands the scope of thse application of fish oil, improves the public nutrition and enhances the value of fish oil.The objective of this work was to microencapsulate fish oil using two types maillard reaction products (MRPs): casein (CAS), soy protein isolated (SPI) with reducing sugars (glucose: lactose=1:1) by spray drying. The preparation method and formulation of fish oil encapsulation was developed. The storage stability of fish oil microencapsulation and the antioxidant properties of wall materials were determined.Effects of different condition on maillard reaction (MR) have been evaluated. MRPs showed that high initial pH values would enhance the MR speed. Increasing heating time of MR mixtures and concentration of reactants, browning increased fast and colour darkened which indicated an increase in a* and b* values, a decrease in L.The antioxidative properties of MRPs prepared by heating CAS and SPI with reducing sugars were examined. The reducing power, inhibition on autooxidant of lecithin liposome system, radical (·OH,DPPH·) scavenging effect of the MRPs were investigated. The results indicated that the MRPs of casein and reducing sugar (CMRPs) possessed higher reducing power, DPPH·radical scavenging activity, inhibition on autooxidant of lecithin liposome system than those of MRPs prepared from soy protein and reducing sugars (SMRPs). The antioxidant capacity was related to concentrate and reaction time of MR. The reducing power,·OH and DPPH·radical scavenging activity of CMRPs were increased with increasing of reaction time. At the same reactant concentration the antioxidant capacity of MRPs was increased with increasing of heating time.The analyses of GC-MS showed that the headspace volatile compounds in MRPs included alcohols, acids, esters, aldehydes, ketoses, phenols and heterocyclic compounds. The thiazole, furane, pyrazine, sulfur, nitrogen-containing compounds and hydroxy-containing compounds contributed most to antioxidant activity of maillard reaction products in these compounds.The analyses of the amino acids of MRPs showed that the amounts of lysine (Lys), arginine (Arg), proline (Pro) and some hydrophobic amino acids increased significantly with MR time prolonged. Among them, the most reactive amino acids residues in MRPs mainly were aspartic acid (Asp), glutamic acid (Glu), glycine (Gly), lysine (Lys) and proline (Pro). Results of orthogonal test design of fish oil microencapsulation with MRPs showed that the optimum conditions using SMRPs as wall material were: heating at 80℃for 5h, pH 7.5, with ratio of fish oil to wall material 0.3(w/w), and the resulting MEY and MEE were 96.97%, 94.53 % and POV was 73.23 (meq/Kg). With CMRPs as wall material, the optimal parameters of encapsulated fish oil were as follows: heating temperature 105℃, pH 8.5 for 3h, with ratio of fish oil to wall material 0.4(w/w), and the resulting MEY and MEE were 87.56%, 93.19 % and POV was 46.21 (meq/Kg), respectively. In addition, when the spray dryer inlet temperature is 180℃a nd the homogeneous pressure is 35 Mpa with two passes. Both the MEE and MEY of the products were 90% above. SEM micrographs showed that fish oil encapsulation products presented a sphere and folded surface without crack and broken microspheres which indicated the high MEE of the product with MRPs as wall material. Glass transition temperature (Tg) of microencapsulation product with CMRPs as wall material by differential scanning calorimetry (DSC) was at 33.24℃; Tg of microencapsulation products with SMRPs was at 43.07℃which predicted their storage temperature of products.The storage stability of fish oil microencapsulation was studied under different storing temperature. The results showed that high storage temperature has a great effect on appearance and storage stability of products. Compared with gelatin and sucrose as wall material, microencapsules prepared from MRPs show low storage stability duo to low density of wall materials, which had high oxygen permeability and water vapor permeability and it was improved by adding 0.12% pectin into the wall system. The antioxidative effect of products was mainly attributed to that pectin improved the structure of wall material, effectively protected the core material and enhanced the storage stability of the microencapsules.
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