The Preparation And Application In Yogurt Of Enzyme-Modified Starch Based Emulsion Filled Gel

Emulsion filled gel is a semi-solid system that is filled with emulsion droplets,which can simulate fat and delivery fat-soluble active substances in food.In this paper,enzymatic hydrolysis rice starch with low dextrose value(DE,DE<5)was used to prepare emulsion filled gel(ES-EFG)and EFG containing DHA(DHA-EFG).Their properties and applications in stirred yogurt were studied.The main results of this paper are as follows:The effects of DE value,starch concentration and emulsion addition on the rheological properties,texture,freeze-thaw stability and microstructure of ES-EFG were investigated.The results showed that the enzymatic hydrolysis rice starch with low DE(DE<5)could form the stable network structure which is filled with O/W emulsion.With the increase of DE value,the storage modulus G' and loss modulus G'',the gel hardness,and the freeze-thaw stability of ES-EFG decreased.With the increase of starch concentration,G' and G'',the thixotropy recovery,the gel strength and the freeze-thaw stability increased.With the increase of emulsion addition,G' and G'',the thixotropic recovery,the gel strength and the freeze-thaw stability decreased.By changing the DE value,starch concentration and emulsion addition,the properties of ES-EFG can be controlled,which provides a possibility for the application of emulsion filled gel as fat simulate in different kind of food.Enzyme-modified starch based emulsion filled gel containing DHA algal oil(DHA-EFG)was prepared.The rheological properties,in vitro digestibility of starch,in vitro digestibility of oil,oxidative stability of oil and volatile components were determined,which provided a theoretical foundation for the application of emulsion filled gel as a delivery system.The results show that DHA-EFG is pseudoplastic fluid and the flow behavior was characterized using the Herschel-Buckley model.Compared with starch gel,ES-EFG had lower RDS and higher SDS and RS.Compared with DHA emulsion,emulsion filled gel improved the digestibility of fat,which improving the utilization rate of DHA.Emulsion filled gel can reduce the oxidation of oil and improve the oxidation stability,but cannot cover the odor of DHA.The main flavor components of DHA-EFG are alcohols and aldehydes.The properties of low-fat yogurt with DHA-EFG were investigated including texture,rheology,microstructure and storage stability.When the addition of DHA-EFG(DE=1 the weight ratio of emulsion: starch: water is 2.5:1:9)in nonfat yogurt was less than 10%,the quality of nonfat yogurt could be improved and the simulation effect of full-fat yogurt could be achieved.With the addition of DHA-EFG increasing,the firmness,consistency,cohesiveness and index of viscosity of low-fat yogurt increased,and thixotropic recovery decreased.DHA-EFG can effectively reduce the whey precipitation in the preparation and storage process of nonfat yogurt,and has no significant effect on the TA of yogurt.It realizes the effect of improving yogurt quality and DHA fortification.