Preparation Of Probiotic Microcapsules With Peach Gum Polysaccharide As Wall Material Additive And Its Application In Milk Tablets

Probiotics are active microorganisms that can bring health benefits to the host.In order to exert their efficacy,it is necessary to ensure that the number of viable bacteria of probiotics is at least 6 Log CFU/g.However,probiotics have poor tolerance to the external environment,and are easily inactivated.Microencapsulation technology can coat probiotics,mainly by separating the core material from the external environment through a physical barrier,reducing the adverse effects of high temperature,oxygen,moisture,acid,alkali,bile salts,etc.on probiotics.Peach gum polysaccharide(PGP)has the functions of immunity,anti-tumor,scavenging free radicals,anti-aging,anti-infection,lowering blood lipids,lowering blood sugar.China is rich in peach gum,but they are seriously wasted,so the development and utilization of peach gum has great commercial value.The purpose of this paper is to explore the potential of PGP as a wall material for L.plantarum microcapsules,and expand the application field of PGP in food.In this paper,L.plantarum microcapsule dry powder was prepared by complex coacervation method combined with spray drying method,and the effects of PGP combined with soy protein isolate(SPI),sodium caseinate(NC)and whey protein isolate(WPI)on the encapsulation efficiency,storage properties,in vitro digestion properties,and heat resistance properties of probiotics were investigated.The formula with the best comprehensive effect was selected and added to the milk tablet,and compared the same type of market goods presently.The study found:(1)PGP is a heteropolysaccharide composed of arabinose,galactose,xylose,mannose and uronic acid;of which arabinose and galactose are the main components,with a content of 48.21% and 36.93%,respectively.(2)The buffering capacity of SPI and WPI was at the same level(28 mmol/p H),which was significantly lower than that of NC(42.5 mmol/p H).The water holding capacity of NC(3.41 g water /g protein)and SPI(3.01 g water /g protein)were significantly higher than those of WPI(0.55 g water /g protein).The hydrophobicity of NC is 233,higher than 132 of SPI and 64 of WPI.(3)PGP has an excellent protective effect on L.plantarum in spray drying.Under the condition of inlet temperature of 140℃ and outlet temperature of 75℃,the survival rate of L.plantarum is 64.78%,which significantly improves the survival rate of L.plantarum in microcapsules.This suggests that PGP has the potential to act as a heat protectant during spray drying.(4)In gastrointestinal tolerance experiments,SPI-PGP,NC-PGP and WPI-PGP microcapsules all effectively improved the survival rate of L.plantarum in in vitro digestion.The study found that the addition of PGP would enhance the digestion properties of SPI-based and NC-based microcapsules in vitro,but would have adverse effects on WPI-based microcapsules.The optimal wall material formulation was SPI:PGP=3:1,the survival rate of probiotics decreased by only 0.88 Log CFU/g during the 6 h in vitro digestion.The FT-IR results showed that there was a strong electrostatic interaction between PGP-SPI and PGP-NC,and the formed composite wall material provided a better protection effect for probiotics.(5)Through scanning electron microscope(SEM)observation,it was found that the SPI-based and NC-based microcapsules with PGP show smooth and intact surfaces,even the severely shrunken WPI-based microcapsule started to be full and round after the addition of PGP.The addition of PGP has no significant effect on the damp heat resistance of NC-based and WPI-based microcapsules,but the addition of PGP has a greater effect on the SPI-based microcapsules.The optimal wall material formula is SPI: PGP=3:1,after heating at 65℃ for 30 min and 75℃ for 10 min,the viable count of probiotics in the microcapsules decreased by only 1.91 Log CFU/g and 1.08 Log CFU/g,respectively.(6)After synthesizing various indicators,it was determined that the formula of L.plantarum microcapsules prepared by SPI and PGP complex coagulation method is more prominent,and SPI: PG=3:1 microcapsules was the best.Under this formula,the bacterial viability in the microcapsules reached 8.7 Log CFU/g after spray drying,and only lost 0.4 Log CFU/g after 8 weeks of storage at 4°C.The viability of L.plantarum remained at about 7.88 Log CFU/g,inactivation of 1.91 Log CFU/g at65°C for 30 min and inactivation of 1.08 Log CFU/g at 75°C for 10 min.(7)The optimal formula of L.plantarum microcapsule milk tablet is: whole milk powder 50%,skimmed milk powder 32.85%,xylitol 7.5%,citric acid 0.4%,maltodextrin 7.5%,L.plantarum microcapsule 1.75%.The diameter of the milk tablet is(12.06 ± 0.02)mm,the appearance is light yellow,the color is uniform,the milk taste is rich and not greasy,and the taste is smooth and delicate when eating.The moisture content of the milk tablets was(2.80 ± 0.32)%,the ash content was(5.10 ±0.28)%,and no E.coli,moulds and yeasts,Staphylococcus aureus and Salmonella were detected.The concentration of viable bacteria in microcapsule milk tablets was significantly higher than that of market goods,which claimed has a great number of probiotics,and the number of viable bacteria was 6.5 Log CFU/g even after 6 h of simulated in vitro digestion.The number of viable bacteria in the probiotic microcapsules decreased by 0.5 Log CFU/g and the hardness was 79.4 N after storage at 25℃ for 8 weeks;the number of viable bacteria decreased by 0.2 Log CFU/g and the hardness was 78.8 N after storage at 4℃ for 8 weeks.