Fabrication Of OSA-starch/Chitosan High Internal Phase Emulsion By Regulating Microenvironment And The Encapsulation Of ?-carotene

High internal phase emulsions(HIPEs),as a kind of highly concentrated emulsion systems,have been widely applied in food field.However,there are some limitations in the fabrication of HIPEs due to the high cost or adverse health effects of conventional emulsifiers(synthetic surfactants or inorganic solid particles).Therefore,the demand of green,safe,and sustainable HIPEs fabrication method is increasing recently in food industry,and it is of significant importance in economy to fabricate environmentally friendly HIPEs.Polysaccharides as a type of natural food substance have been widely applied in food field due to their rich source and good biocompatibility.Meanwhile,they can be used as stabilizer and emulsifier in the fabrication of emulsion systems which could be attributed to their amphipathicity.In this work,the OSA-starch will be employed as the main emulsifiers,and their interfacial behavior at the oil-water interface was adjusted by altering the water phase microenvironment,and the physical,chemical properties,and microstructure of polysaccharide-based HIPEs were investigated.Meanwhile,the interfacial behavior of chitosan and OSA-starch complexes in different water phase microenvironment and the influence of these on the structure of HIPEs were studied.Then,the application of polysaccharide-based HIPEs fabricated by regulating microenvironment in the encapsulation and delivery of oil-soluble nutrient was investigated.The results were as follows:A high internal phase emulsion(HIPE)was firstly fabricated with octenyl succinic anhydride modified starch through simple shear dispersion.The impact of the emulsifier level,p H,and ionic strength on the rheology,microstructure,interfacial properties,water binding and thermal stability of the HIPE was determined.The results indicated that HIPEs could be formed at a suitably modified starch concentration(?3wt%),a wider range of p H(3 to 7)and all test salt levels(0 to 400 m M Na Cl).Encapsulation of a sensitive hydrophobic nutraceutical(?-carotene)within the HIPEs could improve its chemical stability under UV exposure,and the degradation ratio was fairly similar at all test p H values.The ?-carotene stability and bioaccessibility during in vitro digestion were improved by encapsulation into HIPEs,but their values depended on p H to some extent.In order to reduce the demand of the high concentration of OSA-starch(?3 wt%)in the fabrication of HIPEs,the electrostatic interaction between polysaccharides was adjusted to prepare the polysaccharide complexes and improve their interfacial behavior,the influence of polysaccharide complexes on the construction of stable HIPEs and their stability also have been investigated.The results shown that the wettability of OSAstarch was enhanced with the addition of positively charged chitosan which improved from 36.83±1.49 to 74.20±1.08,and the particle size,surface charge,and interfacial behavior could be altered by adjusting the p H of the water phase microenvironment and the concentration of chitosan.The concentration of OSA-starch decreased from 3 wt%to 1 wt% in the fabrication of HIPEs with the presence of chitosan,and the HIPEs could be transformed from liquid-like to solid-like by altering the water phase microenvironment.Moreover,the ?-carotene encapsulation ability of polysaccharide-based HIPEs fabricated by adjusting the water phase microenvironment and the bioavailability of encapsulated ?-carotene were investigated.The carotenoid loading capacity of the HIPEs was around 20-fold higher when octenyl succinic anhydride(OSA)-starch/chitosan complexes were used than when only OSA-starch was used.This impact could be mainly assigned to the capacity of the former HIPEs to trap carotenoid crystals in a stable form.The OSA-starch/chitosan complexes were shown to absorb on the oil droplets interface and form a 3D network in the aqueous phase,which helped to prevent droplet coalescence induced by ?-carotene crystal.The rheological properties of the carotenoid-loaded HIPEs could be controlled(from fluid-to solid-like)by adjusting the p H of the aqueous phase,as this alters complex formation.CLSM results proved that the p H influenced the absorption of the polysaccharide electrostatic complexes to the droplet surfaces.The incorporation of ?-carotene within the oil droplets enhanced its resistance to chemical degradation when exposed to heat,ultraviolet radiation,or gastrointestinal conditions.However,the bioaccessibility of ?-carotene was reduced after encapsulation,which could be due to the reduction in lipid digestion as well as the high fraction of crystalline carotenoids present.Our results provide information that may aid the design and development of edible soft solids containing high carotenoid levels,which may be applied in food and pharmaceutical industry.