Fabrication Of Starch Soluble Fraction Emulsion System And Study On Its Stabilization Mechanism

Based on the wide application of emulsions,the emulsifiers required for the formation and stabilization of emulsions have received extensive attention.The development of natural emulsifiers to replace synthetic emulsifiers and plant-derived emulsifiers to replace animal-derived emulsifiers can be closer to consumers’health needs,which have become hot research topics in recent years.As a polysaccharide,starch is expected to be used as an emulsifier.However,studies have found that the emulsifying ability of native starch is poor and cannot meet the needs of practical applications.A method to improve the emulsifying ability of starch without the introduction of external groups is urgently needed.A starch soluble fraction has been found to have improved emulsifying ability.However,key issues such as the mechanism of the starch soluble fraction stabilizing emulsion and the factors affecting the emulsifying ability have not been investigated.Based on this,this paper has carried out four parts of research content.Firstly,the starch soluble fractions were obtained by physical and enzymatic methods,and the starch soluble fraction emulsion systems were constructed.The effects of s amylose content and molecular weight on the emulsifying of starch soluble fractions were investigated as a theoretical guide for the starch soluble fractions as emulsifiers.Secondly,the ability of starch soluble fractions to construct microcapsules and high internal phase emulsions was investigated as a practical exploration of starch soluble fractions to stabilize new forms of emulsions.The main conclusions of the above research are as follows:（1）Effects of amylose content on the emulsifying ability of starch soluble fractions:Using waxy corn starch,normal corn starch,and high amylose corn starch as raw materials,the starch soluble fractions were obtained by the physical method of gelatinization-centrifugation,and the emulsifying ability of the starch soluble fractions were evaluated.The results showed that the starch soluble fractions obtained from three different amylose content corn starches by physical methods have similar absorption wavelengths（625-630 nm）and peak molecular weights（3.31×10⁵-3.90×10⁵ Da）.On the other hand,the starch soluble fractions have the good emulsifying ability,and the prepared emulsions have good ionic,p H,and thermal stability,especially the emulsion stabilized by the starch soluble fraction obtained from normal corn starch could maintain stability at room temperature for 90 d.In addition,the solid content of the starch soluble fraction solutions was in the order of normal corn starch（13.57 g/L）>high amylose corn starch（8.85 g/L）>waxy corn starch（1.17 g/L）,which was consistent with the storage stability trend of the starch soluble fraction stabilized emulsions.These results indicated that the amylose content of starch affects its emulsifying ability by affecting the dissolution of the starch soluble fraction,which is a more effective emulsifier.（2）Effects of molecular weight on the emulsifying ability of starch soluble fractions:Using waxy corn starch and rice starch as raw materials,the starch soluble fractions with different molecular weights were obtained by enzymatic hydrolysis,and their emulsifying ability and interfacial behavior were evaluated.The results showed that the peak molecular weight range of the starch soluble fractions obtained by enzymatic hydrolysis was 6.298×10⁴-1.219×10⁶ Da.Within this range,the smaller the molecular weight of the starch soluble fraction,the smaller the emulsion particle size（9.99-2.05μm）,the higher the storage stability（1 d-15 d）,i.e.,the stronger the emulsifying ability.In addition,the starch soluble fractions stabilized the emulsions through the Pickering effect,and when the molecular weight of the starch soluble fraction is small enough,an elastic interfacial film could be formed faster while being more resistant to rupture.These results indicated that the molecular weight of starch affects its emulsifying ability.The weekly emulsifying starches can be converted into more effective emulsifiers by reducing the molecular weight.（3）Microcapsules encapsulated by starch soluble fractions:Using normal corn starch as raw material,corn starch soluble fraction was obtained by the physical method of gelatinization-centrifugation,and the commercial soluble starch was regarded as another starch soluble fraction obtained by the enzymatic hydrolysis,the ability of corn starch soluble fraction and commercial soluble starch to encapsulate microcapsules was evaluated.The results showed that microcapsules with good performance could be prepared by dispersion-spray drying using corn starch soluble fraction and commercial soluble starch as the only wall material under the condition of 2:1 wall material to core material,respectively.In which the molecular weight of the starch soluble fraction played a decisive role in the performance of the microcapsules.The peak molecular weight of the corn starch soluble fraction was 3.537×10⁵ Da,and the peak molecular weight of the commercial soluble starch was 2.720×10⁴ Da.The microcapsules they prepared have similar encapsulation efficiency（88.58%-89.56%）and sustained release properties.However,they differ in more properties:commercial soluble starch encapsulated microcapsules have more rounder granules and faster in vitro digestion;The encapsulation yield of the corn starch soluble fraction encapsulated microcapsule and the commercial soluble starch encapsulated microcapsule was 64.26%and 91.02%,the particle size(d_4,3)was 37.70 and 7.39μm,the boiling water solubility was 74.26%and 99.22%,and the rehydration stability was 2 h and 7 d,respectively.（4）High internal phase emulsions that starch soluble fractions participated in stabilization:The commercial soluble starch was regarded as the starch soluble fraction obtained by the enzymatic hydrolysis,starch-whey protein isolate complexes were prepared,and the ability of the complexes to prepare high internal phase emulsions was evaluated.The results showed that the starch-whey protein isolate complex could be formed,the complex has reduced UV absorption at 200 nm and reduced fluorescence intensity at 340 nm.Besides,this complex has stronger emulsifying properties than the commercial soluble starch and whey protein isolate and could form a strong interfacial film at the oil-water interface,thus having the ability to stabilize high internal phase emulsions.On the other hand,the main force for stabilizing the emulsion of starch-whey protein isolate complexes was the steric hindrance force,followed by the electrostatic repulsion force.In addition,the high internal phase emulsion stabilized by starch-whey protein isolate complex has a better protection effect onβ-carotene than the whey protein isolate stabilized high internal phase emulsion,there was still 17.95%retention ofβ-carotene after 72 h UV irradiation.Meanwhile,in addition to the isoelectric point of whey protein isolate,the high internal phase emulsion stabilized by the starch-whey protein isolate complex was more stable in an acidic environment,especially the high internal phase emulsion remained stable in a high ionic strength environment.In summary,the starch soluble fractions obtained by physical and enzymatic methods have improved emulsifying due to improved oil-water interfacial adsorption.They are a kind of emulsifier with a"clean label"suitable for the preparation or participation in the preparation of oil-in-water emulsions,microcapsules,and high internal phase emulsions.