| Algal oil is a functional oil,which is extracted from marine algae.It is rich in omega-3 polyunsaturated fatty acids,especially docosahexaenoic acid(DHA),which has been associated with the prevention of cardiovascular disease,infant dysplasia and the like.Unfortunately,incorporation of algal oil into foods has several obstacles,including high oxygen sensitivity,low water solubility and rapid loss of activity,which limit its applications in food formulation.This study aimed at providing a novel approach for improving the physicochemical stability,solubility and bioavailability of algal oil microcapsules through formation of electrostatic interactions and prebiotic carbohydrates systems composed of starch octenyl succinate(OSA starch),inulin(IN),maltodextrin(MD)and chitosan(CS).The main research contents listed as follows:Firstly,using single factor and response surface design to optimize emulsion formulation and preparation parameters of algal oil microcapsules.The optimal preparation conditions were determined as follows: 10% oil load,1:2.5 core wall ratio,15 minutes ultrasonic treatment,300 W ultrasonic power,the ratio of OSA starch: other wall materials(MD + CS + IN)was 5: 1;Besides,the effects of different wall material systems on the rheological properties and stability of the emulsions were investigated.The results showed that IN could significantly reduce the viscosity of the emulsion(p <0.05),and CS could improve the stability of the emulsion.Secondly,algal oil microcapsules were prepared by spray drying,and the effects of different wall material systems on their properties were discussed.The results showed that the encapsulation efficiency(EE)of OSA / MD / IN microcapsules was 98.57%,which was significantly higher than the EE of other microcapsules(p <0.05);Compared to OSA/CS particles,the addition of IN(OSA / CS / IN particles)increased the cold water solubility and wettability time of the microcapsules by 4.96% and 749 s(p < 0.05),respectively.Infrared spectrum indicated the formation of hydrogen bonding force between IN and water-soluble materials;In addition,microcapsules containing CS(OSA / CS / IN and OSA / CS)showed the stronger oxidation stability,and OSA/CS/IN particles had the longest oxidation induction period(three times that of bulk oil)than others;The hygroscopic characteristics of microcapsules found that the OSA / CS / IN microcapsules were the only samples that could maintain physical stability under the high humidity;The thermal stability of algal oil microcapsules were evaluated by thermogravimetric analysis.Comparing the pure algal oil to the algal oil microcapsules,it was observed that the temperature of the maximum weight loss rate of algal oil shifted from 378°C to 400°C,suggesting the protection of the wall materials on algal oil.Finally,the storage stability and release characteristics of the microcapsules in-vitro were studied.According to the analysis of oxidation reaction kinetics,the oxidation reaction of the algal oil microcapsules changed from first order oxidation reaction kinetics to the zero ones after encapsulation.The storage time of the bulk oil and the OSA / CS / IN microcapsules were 160 d and 368 d at room temperature;The oven accelerated oxidation test showed that the DHA retention rate of the OSA / CS / IN microcapsules was 61.43%,which was 2.65 times than that of bulk oil and 1.35 times than that of control group(OSA),implying that the algal oil had enhanced storage stability after being encapsulated by OSA / CS / IN system;The free fatty acids(FFA)release percentage of the three microcapsules in simulated gastric fluid(SGF)were all less than 7%.The OSA / CS / IN microcapsules showed the lowest release percentage(4.24%),which meant it was hard to loss activity in gastric stage;The small intestine simulation results showed FFA release percentage was between 52.12% and 68.07%,while the value of OSA microcapsules was significantly higher than other samples,which indicated that the OSA / MD / IN and OSA / CS / IN microcapsules were rarely released in stomach,and the majority of the algal oil was released into the small intestine,showing good performance of controlled release. |
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