Study On Microencapsulation Of Fish Oil With Considerable Amounts Of ω-3 PUFAs

Fish oil has considerable amounts of polyunsaturated fatty acids,e.g.,EPA & DHA so that it owns good healthy function.But EPA & DHA are easily oxidizeable,and the fishy smell and fat-soluble property of fish oil also limit its application as a nutrition additive. Microencapsulation can prevent fish oil from oxidation and deterioration,and weaken its fishy smell.Microencapsulation by coacervation is the phase separation of one or many hydrocolloids from the initial solution and the subsequent deposition of the newly formed coacervate phase around the active ingredient suspended or emulsified in the same reaction media.After hardened,the wall of microcapsules forms web structure,so the microcapsules produced by coacrvation possess excellent heat and moistureresistant properties.In this study, fish oil was microencapsulated using complex coacervation of gelatin/gum arabic, transglutaminase(TG) was a cross-linking agent.The preparation technology,ability to anti oxidation and the effect on fishy smell were studied.Preparation technology of microcapsules was investigated,the optimal parameters were found as follows:pH 4.0,the ratio of gelatin to gum arabic was 1:1,colloid concentration was 1%,the ratio of core to wall was 1:2,stirring speed was 300～400 r·min^-1,at these conditions microcapsules were smooth,uniform,spherical and multinuclear.The ratio of TG to gelatin was 25 U·g^-1 gelatin and it solidified the microcapsules for four hours.The antioxidation effect of antioxidant added in preparation technology of microcapsules was investigated.The optimal amount of antioxidant was:vitamin E 1000 mg·kg^-1 and TBHQ 500 mg·kg^-1.After keeping in 80℃water base for 100 min,the morphology of microcapsules did not change;the retention rate of EPA & DHA was 95.85%& 96.73%respectively;and microcapsules were stable.Double encapsulation of complex coacervation microcapsules was investigated.Results showed that:double encapsulation by millard reaction product can protect fish oil from oxidation and reserves the functional ingredients of fish oil.After storage at 45℃for 15 days,the retention rate of EPA & DHA in double encapsulated microcapsules was 94.97%& 96.42%respectively.The superstructure of doubly encapsulated microcapsules was investigated using SEM.Microcapsules after double encapsulated by maltodextrin and gum arabic were shrunken;microcapsules after double encapsulated by millard reaction products were smooth,compact and integral and no holes or cracks were found.Physical properties of double encapsulated microcapsules were studied.The moisture was 2.19%±0.03%,the density was 0.43±0.01 g·mL^-1,and the repose angle was 34.7°±0.5°.Effect of microencapsulation on fish oil flavor was investigated.Volatile compounds that were related with fishy smell were identified by SPME-GC-O-MS.Effect of different drying methods on fishy smell was compared.Milk added encapsulated fish oil was investigated by sensory evaluation.Results showed that;freeze-drying can keep the fish flavor best and reduce the fishy smell;milk added wet fish oil microcapsules had no fishy smell and the acceptability score was the highest.Milk added encapsulated fish oil product by freeze-drying had a higher score in acceptability and fishy smell than by spray drying or vacuum drying.