The Protection Effect Of Different Components For Lactobacillus Plantarum CICC 20270 Based On Single Droplet Drying And Spray Drying

The storage of probiotics in powder form or addition to other products can give them a longer shelf life and the activity of their specific bioactive components is also preserved.In industrial practice,freeze drying is often used to produce probiotics.But in recent years,spray drying has attracted widespread attention due to its advantages of low cost and high benefits.Although the drying time of spray drying is very short compared to freeze-drying,probiotic bacteria are more easily inactivated during drying.Therefore,many studies have focused on optimizing spray drying conditions and product formulations to minimize the loss of probiotic activity.However,due to the fact that the drying process is not visible after the material enters the spray drying tower,the inactivation mechanism of the bacterial cells,the drying history of the droplets,and the protection mechanism of the protective agents against the probiotics during the spray drying process are not yet clear.Therefore,in this experiment,Lactobacillus plantarum CICC 20270 was used as a research strain,and two kinds of syrups with DE values?glucose values?of 25 and 18 were respectively used as protective agents.The single droplet drying technique was used to study the drying process of individual droplets.The main factors affecting the inactivation of probiotics in the droplets and the protective effect of the protective agent during the drying process.Syrup was used to embed different lipids and L.plantarum CICC20270 to explore the protective effect and mechanisms of each component on the bacterial cells in single droplet drying.In addition,probiotic microcapsules were prepared by spray drying to further explore the protective effect of each component on the bacterial cells in the storage period of microcapsules and simulated digestion in vitro.Also provide some theoretical basis for future application in industrial production.The results of the study are as follows:1.DE25 and DE18 syrups were used as protective agents for Lactobacillus plantarum.The drying parameters,droplet temperature,weight,and bacterial activity,were measured by a single-drop desiccator to investigate the protective effect of DE25 and DE18 syrups on the drying process of L.plantarum CICC 20270.The conclusions are as follows:At 90°C and 110°C,it was observed that the survival rate of bacteria cells in single droplet drying was always higher than that of DE18 syrup when DE25 syrup was used as a protective agent.To investigate the main factors causing the inactivation of L.plantarum CICC 20270 in droplets during the drying process,it was concluded that the bacterial cells were died mainly due to dehydration during the early drying stage.However,the combined effects of high temperature and dehydration resulted in a large number of bacterial deaths in the later period of drying.Due to its better water holding capacity,DE25 syrup protects bacterial cells from damage caused by greater dehydration in the later stage of drying,thus providing better protection than DE18 syrup.The effect of two rice syrups on the growth and metabolism of L.plantarum CICC 20270 was determined by using DE25 and DE18rice syrup instead of or in part to replace the glucose in the culture solution.It was found that when the rice syrup partially replaces glucose,the pH of the bacterial solution increases and the OD₆₀₀ values decreased with the concentration of the rice syrup.The pH value and OD₆₀₀ value of the bacterial solution containing DE25 rice syrup when completely replaced are close to that of the original bacterial solution,that is,the DE25 rice syrup has the same growth promoting effect on the bacterial cells as the DE18 rice syrup.2.Use DE25 and DE18 syrups to embed high melting point palm oil?HMP?,low melting point palm oil?LMP?,and L.plantarum CICC 20270,respectively.First,to investigate the effect of syrups and oils on the viability of bacterial cells using a single droplet dryer.Then,the protective effect of the two components on the microbiological activity of the microcapsules during the storage period was further explored through spray drying.In vitro simulated digestion experiments were performed to analyze the acid resistance and release properties of L.plantarum CICC20270 in the presence of syrups and oils.The following conclusions could obtained:?1?During the single droplet drying experiment at 90°C and 110°C,the final bacterial activity in the droplets containing HMP was higher than that of the LMP droplets.Compared to different DE value syrups,different melting point palm oil had a greater effect on the survival rate of L.plantarum CICC 20270 cells.The differential scanning calorimeter?DSC?shows that the melting enthalpy??H?of HMP is greater than that of LMP.Therefore,the phase change of HMP absorbs more heat during the drying process so that the bacterial cells are protected from partial thermal damage.At the same time,the same experimental results were obtained by measuring the cell survival rate of L.plantarum CICC 20270 microcapsules by spray drying.The survival rate of microcapsules containing HMP was greater than that of LMP microcapsules.?2?The SEM observation of single droplets dried for 5 minutes and the spray-dried microcapsule structure revealed that the DE25 syrup is more conducive to the stability of the surface structure.?3?When L.plantarum CICC20270 microcapsules were stored at 4°C,25°C,and 37°C,the bacterial cell death rate in microcapsules increased gradually as storage temperature increased.At the same time,the survival rate of microcapsules containing HMP at 25°C and 37°C was higher than that of microcapsules containing LMP.When the microcapsules were stored at 25°C under 33%,52%,75%relative humidity,compared with the effects of palm oil with different melting points,different DE value syrups had a greater impact on the survival rate of bacterial cells.And the protection of DE25 syrup is better.?4?After 6 h continuous in vitro digestion of L.plantarum CICC 20270 microcapsules,the microbial activity in DE25/HMP,DE18/HMP,DE25/LMP,and DE18/LMP microcapsules decreased by 3.80,6.03,4.73,5.43 logarithm,respectively,after 2hours of simulated gastric juice.The survival rate of DE25/HMP was the highest,reaching 56.56%.And all the microcapsule samples could release probiotics quickly after entering the simulated intestinal fluid?SIF?.3.After the oils containing different chain length fatty acids,ie,corn oil?long-chain fatty acids?and coconut oil?medium-chain fatty acids?were separately made into emulsions with different DE value syrups,L.plantarum CICC 20270 was suspended therein.Using single-drop drying and spray drying to explore the protective effect and mechanism of components.The following conclusions were obtained:?1?During single drop drying experiments at 90°C and 110°C,different DE value syrups had greater influence on the final survival rate of L.plantarum CICC20270.And the protection of DE25 syrup is better.However,the difference in oils shows little difference between the bacterial cell viability.By analyzing the moisture content and temperature of the droplets,it was found that L.plantarum CICC 20270cells were mainly damaged by high temperature during the drying process.The DE25syrup had better protection effect at high temperature,but its protection mechanism needs further study.?2?After spray dried to obtain L.plantarum CICC 20270microcapsules,together with the single droplets dried for 5 min by SEM observation,the results showed that the DE25 syrup is still more conducive to the stability of the surface structure.?3?When analyzing the heat-resistance properties of microcapsules,heat-treatment of L.plantarum CICC 20270 microcapsules at 55°C,65°C,and 75°C was performed.Under 55?heat treatment conditions,there was no significant difference in the number of viable cells.After heat treatment for 1 min and 10 min at65?,the lowest microbial activity was DE25/coconut oil and DE18/coconut oil microcapsules.The survival rates were 75.66%and 49.82%,respectively.After heat treatment at 75?for 1 min and 10 min,the bacteria activity in DE18/coconut oil microcapsules was the lowest,which was 38.40%and 15.08%,respectively.It was found that corn oil microcapsules had better heat resistance than coconut oil microcapsules.?4?When the microcapsules were stored at 4,25,and 37°C,the viability of the bacteria in the corn oil microcapsules was higher than that of the coconut oil microcapsules.When the microcapsules were placed at 33%,52%,and75%relative humidity at 25°C,the difference in oil was not significantly different by measuring the number of bacteria in the microcapsules.Compared to DE18 rice syrup,the use of DE25 rice syrup as a wall material facilitates the stability of the microcapsules.?5?The in vitro digestion experiments of L.plantarum CICC 20270microcapsules showed that the survival rate of DE25/coconut oil microcapsules was the highest after continuous 6 hours of digestion,which was 52.71%.The survival rates of bacteria in DE25/corn oil,DE18/corn oil,DE18/coconut oil microcapsules were 41.78%,41.42%,and 50.55%,respectively.In the microcapsules with the same fat as the core material,DE25 rice syrup provides better gastric acid digestion than DE18 rice syrup.The coconut oil is more conducive to the survival of L.plantarum CICC 20270 than corn oil.According to the results of in vitro digestion,the use of DE25 rice syrup as a wall material for embedding coconut oil and L.plantarum CICC20270 is more conducive to the viable effect of viable bacteria released through strong stomach acid and reaching the intestine.