Mechanism And Application Of Trehalose To Enhance Probiotic Viability Of Whey Protein/Pullulan Microcapsules

Probiotics are one of the important components of the human intestinal tract,with a variety of physiological functions.However,probiotics are susceptible to loss of viability due to adverse conditions such as p H,water activity,oxygen and temperature.Microencapsulation technology is commonly used to protect probiotics and to control their release into the intestinal tract.The team’s previous research utilized whey protein concentrate(WPC)and pullulan(PUL)to encapsulate lactic acid bacteria by preparing gel through heating,which could improve the survival rate of lactic acid bacteria in simulated gastrointestinal environment,but the prepared probiotic microcapsule had short storage period(90 d),and there was still room for improvement in the number of viable bacteria and encapsulation rate.In this study,WPC/PUL/TRE gel was prepared by adding trehalose(TRE)to WPC and PUL,and the prepared gel was used as microcapsule wall material to encapsulate Lactobacillus plantarum to obtain probiotic microcapsule products with high probiotic viability,economic benefits and application potential.The main contents and results of this study are as follows:1.The effects of TRE concentration and the ratio of L.plantarum suspension to WPC/PUL/TRE gel on the viability of the encapsulated L.plantarum were investigated by the single-factor test using the encapsulation rate of L.plantarum after freeze drying as an index.The optimal TRE concentration was obtained as 5%(w/v),the optimal ratio of L.plantarum suspension to WPC/PUL/TRE gel was 1:4(v:v),and the highest encapsulation rate of L.plantarum was 94.36±1.06%.2.The effects of TRE on the gastric acid resistance,enteric solubility and storage stability of the WPC/PUL probiotic microcapsule were investigated.After 4 h treatment in simulated gastric juice(SGJ),the survival rates of encapsulated L.plantarum in WPC/PUL and WPC/PUL/TRE probiotic microcapsules were 92.54±0.27% and 94.37±0.36%,respectively,and the addition of TRE improved the viability of encapsulated L.plantarum in SGJ.After 2 h treatment in simulated intestinal juice(SIJ),L.plantarum was completely released from WPC/PUL and WPC/PUL/TRE probiotic microcapsules.After 480 d of storage at 4°C,the survival rates of L.plantarum encapsulated in WPC/PUL and WPC/PUL/TRE probiotic microcapsules were 81.60±0.78% and95.88±0.81%,respectively,the addition of TRE improved the viability of L.plantarum by increasing the glass transformation temperature of probiotics microcapsules during long-term storage.3.The effect of TRE on the membrane integrity of encapsulated L.plantarum in WPC/PUL probiotic microcapsules was investigated by flow cytometry,the effects of TRE on the structure and water-holding capacity of WPC/PUL gel were investigated by scanning electron microscopy and the drying kinetic experiment,and the effect of TRE on the interaction of WPC/PUL gel was investigated by Zeta-potential,Ellman’s reagent,ANS fluorescence probe and infrared spectroscopy.The results indicated that TRE weakened the hydrophobic interactions,disulfide bonds and hydrogen bonds between proteins and polysaccharides,which was not conducive to the formation of gel network structure,but TRE improved the cell membrane integrity and waterholding capacity of wall materials,thereby increasing the viability of L.plantarum during freeze drying.4.The effect of TRE on the application of the WPC/PUL probiotic microcapsule in fruit juice was explored.The results showed that the citric acid buffer and raspberry juice containing probiotic microcapsules had the best storage effect at 4℃ and 25℃,respectively.The addition of TRE could improve the membrane integrity of encapsulated L.plantarum in a low p H environment,thus enhancing the viability of encapsulated L.plantarum in acidic fruit juices such as raspberry juice.In summary,in this study,L.plantarum was encapsulated by the WPC/PUL/TRE gel.TRE improved the tolerance of specific cells to adverse environments by improving the cell membrane integrity and water-holding capacity of wall materials,which provided a theoretical basis for the preparation and application of probiotic microcapsules,resulting in a probiotic microcapsule product with high probiotic activity,economic benefit and application potential.