Construction And Performance Of Encapsulation System Of Probiotics Based On Electrospraying Technology

Probiotics are defined as non-pathogenic microorganisms that can exert beneficial effects on the health of host.To exert health effects,the survival amounts of oral intake probiotics in colon should be more than 7 log CFU/m L.However,the viability of probiotics declines rapidly during processing and gastrointestinal(GI)delivery,thus it is essential to develop efficient microencapsulation systems to improve the survivability of probiotics under adverse conditions.It has been proved that multi-layered microcapsules have better protective effects against adverse conditions than monolayer microcapsules.However,the existing layer-by-layer encapsulation procedure is complex which needs to be simplified,and some operation conditions of encapsulation technologies are harsh.The electrospraying technology could realize the formation of multi-layered microcapsules in one-step under mild conditions.Previous studies have reported that coaxial electrospraying had better encapsulation effect than uniaxial electrospraying.However,there are few researches on the encapsulation of probiotics by coaxial electrospraying presently,and the studies on the resistibility of encapsulated probiotics in the resulting microcapsules to the harsh GI conditions are fewer.Herein,in this study,coaxial electrospraying method was applied to prepare nove multi-layered microcapsules,and the charteristics and performance of the resulting microcapsules were analyzed.Prebiotics can not only help improving the viability of probiotics,but also be benefical to the health of body.However,there are very few reports on the co-encapsulation of probiotics and prebiotics by electrospaying.Therefore,to further improve the encapsulation efficiency and survival rate of probiotics,the prebiotics such as fish oil and fructooligosaccharides were added into probiotics microcapsules in this study and the obtained microcapsules were applied to actual food samples.The main research results of this paper are as follows:1.Preparation and performance of microcapsules loaded with Lactobacillus plantarumLactobacillus plantarum was used as model probiotics,and the multi-layer microcapsules loaded with Lactobacillus plantarum(SPI-L-P)were prepared by coaxial electrospraying technology.Using the encapsulation rate(EE)and the survival rate(SR)of probiotics after exposure to continuous simulated gastrointestinal fluid as indicators,the suitable preparation conditions were determined as follows:the concentrations of soybean protein isolate(SPI),sodium alginate(SA)and pectin(PEC)were 3%,2.5%and 2%,respectively,and the voltage was 12 k V.The EE and SR of SPI-L-P were 89.4%and 90.7%,respectively,and more than90%of the probiotics could realize colon-targeted release.The results of scanning electron microscopy(SEM)confirmed that the probiotics had been successfully encapsulated in the SPI-L-P,but the surface of the microcapsules were damaged.Fourier transform infrared spectroscopy(FTIR)and X-ray diffraction(XRD)analysis showed that there existed interactions among SPI,SA and PEC of the microcapsules.Thermogravimetric analysis(TGA)showed that SPI-L-P had good thermal stability.The SPI-L-P improved the thermal stability of probiotics,and the SR of probiotics increased by 32.7%compared to free probiotics after treatment at 70 ~oC for 30 min.Compared with 25 ~oC,4 ~oC was more suitable for microcapsule storage,and the SPI-L-P had good storage stability at 4 ~oC.2.Preparation and performance of microcapsules loaded with prebiotic/Lactobacillus plantarumIn order to further improve the performance of microcapsules,fructooligosaccharides,fish oil and fructooligosaccharides/fish oil were added into the nuclear layer of the above microcapsules loaded with Lactobacillus plantarum.And the microcapsules loaded with fructooligosaccharides/Lactobacillus plantarum(SPI-F-L-P),fish oil/Lactobacillus plantarum(SPI-O-L-P),and fish oil/fructooligosaccharides/Lactobacillus plantarum(SPI-O-F-L-P)were prepared,respectively.The EE and SR of these three synbiotics groups were higher than those of SPI-L-P,and the performance of SPI-O-F-L-P was the best.The EE and SR of SPI-O-F-L-P were 95.9%and 95.5%,respectively.The SEM results showed that the distribution of probiotics in SPI-O-F-L-P was the densest,and the surface of which was smooth and compact.The FTIR and XRD results showed that there also existed interactions among the wall materials of three synbiotics microcapsules.The TGA results showed that the thermal stability of these three synbiotics microcapsules was higher than that of SPI-L-P.Similarly,these three synbiotics microcapsules also improved the thermal stability of probiotics.After heating treatment at 70 ~oC for 30 min,the probiotics viability of three synbiotics microcapsules was higher than that of SPI-L-P,with SPI-O-F-L-P having the highest probiotics viability.The three groups of freeze-drying synbiotics microcapsules had quite a good gastrointestinal tolerance,and the SR of probiotics reached 80-85%after simulated gastrointestinal fluid treatment,which was higher than 77%of SPI-L-P,while the freeze-dried free bacteria was completely inactivated at this time.Similarly,4 ~oC was more suitable for microcapsule storage compared to 25 ~oC,and the synbiotics microcapsule had good storage stability at 4 ~oC,which was also higher than the corresponding value of SPI-L-P.3.Application of probiotic microcapsulesThe above four groups of microcapsules were placed in pear juice at 4 ~oC to investigate their storage stability in pear juice and the change of p H of pear juice.After 42 days,the SR of probiotics in microcapsules was significantly higher than that of free bacteria(75-82%vs.27.2%),and the viability of probiotics in the three groups of microcapsules with prebiotics added was also higher than that without prebiotics added,and the viability of probiotics in SPI-O-F-L-P was the highest(7.6 log CFU/m L).The results showed that the microcapsules had a good protective effect on probiotics,and the addition of prebiotics could further enhance the protective effect.In addition,the p H change of pear juice with microcapsules was much lower than that with free probiotics,while the p H change of pear juice with SPI-O-F-L-P was the least,which indicated that microencapsulation could lead to controlled release of probiotics,thus improving the quality of the probiotic product during storage.This study provides a theoretical basis for the construction of probiotic multi-layer microcapsules with high encapsulation rate and high stability based on electrospraying technology,and will promote the application of electrospraying technology in the field of functional foods.