Structural Design And Performance Control Of W/O Based Multiple Emulsions Made From Beeswax

People were pursuing a higher quality of life under the trend of rapid development of economy and society.Food-grade emulsions with rich nutrition were welcomed by more and more individuals.Multiple emulsion provided a new idea for the development of novel foods.Emulsion was a stable system formed by mixing two mutually insoluble phases,which exploited the advantages of single aqueous solution and pure oil system.In view of this,the present study was designed to fabricate edible W/O emulsions,and the emulsions were gradually optimized,and then multiple emulsions with good storage stability and excellent freeze-thaw stability were fabricated.The main research contents and results were as follows:(1)The safety and edibility of the emulsions would be weakened because of the addition of surfactants,therefore,the beeswax-based oleogels were used to prepare the W/O emulsions rather than surfactant.The preparation method was as follows: At first,the beeswax-soybean oil oleogels with thermo reversibility were prepared.Afterwards,the W/O emulsions were fabricated by injecting water into the molten oleogel under the condition of magnetic stirring at 20 °C.The obtained emulsion had long-time stability,and there was no apparent phase separation or oil leakage after 60 days of storage.In this system,beeswax served as a stabilizer for both oleogels and oleogel-based emulsions.The sol-gel melting temperature of the oleogel increased gradually with the increase of beeswax content.The sol-gel melting temperature of the oleogel was 37 ± 0.5 °C by regulating beeswax content to 4% w/w.The droplet size of the prepared W/O emulsions had an opposite relationship with the amount of beeswax,which meant if the content of beeswax increased,the droplet size of the W/O emulsion would be reduced.When the beeswax content was 4%w/w,the droplet diameter of the emulsion was around 9 ?m.Thermo-reversible and thixotropic properties of oleogels were both retained for emulsions.Furthermore,both oleogels and oleogel-based emulsions had compact gel-like structures.(2)To further optimize the structure of W/O emulsions,the prepared emulsions could encapsulate not only hydrophobic components but also water-soluble bioactive ingredients.Therefore,the water-in-oil(W/O)emulsions with smaller droplet diameter served as original water phase,then oil-in-water-in-oil(O/W/O)emulsions were fabricated.The preparation method was as follows: 3% w/w carboxymethyl chitosan was used as the stabilizer to prepare O/W emulsion by high-speed shearing,and then the O/W emulsion was dispersed into the oleogel under magnetic stirring to prepare O/W/O emulsions.From the micrographs of O/W Pickering emulsions,the droplet size of the O/W emulsion gradually decreased with the increase of carboxymethyl chitosan content.When the carboxymethyl chitosan content was fixed at 3% w/w,the emulsion with the higher the proportion of O/W emulsion had more concentrated emulsion droplets.From the micrographs of O/W/O emulsions,it could be observed that the smaller droplets of the O/W emulsion were all well wrapped in the larger droplets of W/O emulsions,and with the increase of beeswax content,the droplet size decreased gradually.In addition,the O/W/O emulsions had good physical stability.When the O/W emulsion content was 10%(v/v)and the beeswax content was 6% w/w,there was no apparent phase separation or oil leakage after 30 days of storage at room temperature.Moreover,the O/W/O emulsions were also able to be solidified after treatment.To be specific,they were heated for 5 minutes at 60 °C,and then the temperature was reduced to 25 °C,the O/W/O emulsions became solid after10 minutes.From the result of the rheological tests,the storage modulus and loss modulus of the O/W/O emulsions increased significantly,the gel network structure was enhanced,indicating that the external phase of the O/W/O emulsions could be solidified.(3)In order to weaken the fluidity of O/W/O emulsions and make the emulsions solidify without the above treatment.The structure of O/W/O emulsions was improved by the gelation of the water phase.3% w/w gelatin was used as stabilizer to prepare O/W emulsion,and the method of high-speed shearing was adopted in the process,the O/W emulsion could be changed into the emulsion gel.The O/W/O emulsion was prepared by magnetic stirring when the O/W emulsion was dispersed into the oleogel before gelation.The O/W/O emulsion could be used for food storage and transportation at low temperature because of its excellent freeze-thaw stability.Furthermore,the water phase of the O/W/O emulsion were able to be solidified,the emulsion structure of oil-in-solid-in-oil(O/S/O)was formed.Afterwards,the O/S/O emulsion was solidified further,which was heated at60 °C for 3 min,and then it was cooled to normal temperature.Therefore,the oil-in-solidin-solid(O/S/S)emulsion was fabricated.In summary,the W/O emulsions and O/W/O multiple emulsions based on the oleogel both had good stability.The emulsions could be used as fat substitute,and also provided a new clue for the development of healthy food as and nutritional supplement.