Effect Of W/O/W Emulsion Based On Probiotics And Fish Oil In Improving Ulcerative Colitis And Its Application In Yogurt

The use of free（non-encapsulated）probiotics has limitations,as they are prone to destruction and degradation during food processing and gastrointestinal digestion.Therefore,developing protective probiotic delivery systems is of great importance.Well-designed probiotics delivery systems can enhance the stability of probiotics during food processing and digestion,ensuring that a greater proportion of live probiotics can reach and colonize the colon.These systems can be used to improve inflammatory bowel disease without causing side effects,such as increased drug resistance and disruption of intestinal microbiota.Intestinal inflammation,which causes diarrhea and other forms of intestinal discomfort,has also been linked to various extraintestinal diseases,such as arthritis,fatty liver disease and conjunctivitis.Research is being conducted on the potential value of probiotics to mitigate inflammation and improve intestinal health through dietary interventions.Probiotics can regulate the protective role of the intestinal barrier,regulate the immune system and intestinal flora,and produce beneficial factors.Therefore,the use of probiotics can reduce the need for antibiotics in people,thereby reducing their potential side effects and the growth of antibiotic resistance in pathogenic bacteria.To explore the impact of the delivery system on probiotics,proteins and polysaccharides were utilized as raw materials.Firstly,W₁/O/W₂emulsion co-embedded with probiotics and fish oil was constructed to explore the protective effect of the delivery system on probiotics and its influence on intestinal adhesion ability of probiotics.Secondly,dextran sodium sulfate（DSS）was used to construct ulcerative colitis（UC）mice,and the mechanism of W₁/O/W₂emulsion to improve intestinal inflammation was investigated.Finally,the W₁/O/W₂emulsion was added to yogurt to explore its effect on physical and chemical properties and the flavor of yogurt.The main research contents and results are as follows:（1）Construction and properties of W₁/O/W₂emulsion co-embedded with probiotics and fish oil:The probiotic suspension was dispersed in the oil phase composed of fish oil and medium chain triglyceride to form W₁/O emulsion.These emulsions were homogenized with an aqueous solution containing soy protein isolate and sodium alginate to form W₁/O/W₂emulsions.Fish oil can promote the growth of probiotics and increase their ability to adhere to the intestinal mucosa.Sodium alginate improved the viscosity,stability and encapsulation rate of probiotics,which were mainly attributed to the interaction between sodium alginate and adsorbed soy protein.Through optimization,W₁/O/W₂emulsion with higher encapsulation rate of probiotics（>96%）could be obtained.In addition,in vitro simulated digestion experiments showed that W₁/O/W₂emulsion significantly increased the number of probiotics alive after passage through the entire gastrointestinal tract（4.95×10⁶CFU/m L）,resulting in a higher survival rate of probiotics（70.78%）.Thus,encapsulating probiotics in W₁/O/W₂lotions might enhance their survivability under gastrointestinal conditions,thereby increasing their efficacy in functional foods.（2）Study on the mechanism of W₁/O/W₂emulsion co-embedded with probiotics and fish oil to improve intestinal health of UC mice:8-week-old C57BL/6J male mice were selected as the research object,and the UC mouse model was constructed by 2.5%DSS induction for 7 days to explore the mechanism of W₁/O/W₂emulsion to improve intestinal health.By analyzing the colonic tissue morphology and intestinal flora of mice,the results showed that W₁/O/W₂emulsion co-coated with probiotics and fish oil promoted the secretion of tight junction proteins（Occludin,ZO-1 and Claudin-1）and short-chain fatty acids（acetic acid,propionic acid,butyric acid,isobutyric acid and valeric acid）in intestinal tract.It inhibited the production of pro-inflammatory factors（TNF-αand IL-1β）,and promoted the growth and reproduction of probiotics such as Butyvibrio,Riyanaceae and Clostridium.Thus,a healthy intestinal microenvironment was created,which inhibited the damage of pathogenic bacteria to the intestine,slowed down the development of inflammation,and was conducive to the recovery of intestinal health.（3）Effects of W₁/O/W₂emulsion co-embedded with probiotics and fish oil on physical and chemical properties and the flavor of yogurt:The constructed W₁/O/W₂emulsion was added to yogurt to explore the influence on yogurt during fermentation and storage.W₁/O/W₂emulsion was added to yogurt to improve its water holding capacity.The W₁/O/W₂emulsion added before fermentation was affected by fermentation and its structure was damaged.The probiotics and fish oil leakage in it resulted in excessive fermentation and adverse flavor.However,adding W₁/O/W₂emulsion to yogurt after fermentation did not have the above effects,and its p H,total acid and flavor were closest to that of yogurt without emulsion.In addition,the effects of W₁/O/W₂emulsion on various indexes during the whole storage period were the same as those during fermentation.This was because probiotics can be wrapped in the internal W₁phase,and the structure of the double emulsion separates them from yogurt,avoiding its interference on yogurt.Therefore,the structure of W₁/O/W₂emulsion could remain intact.In conclusion,the electrostatic interaction between soy protein isolate and sodium alginate,in conjunction with the fish oil loaded in the oil phase,collectively enhanced the stability of W₁/O/W₂emulsion and the encapsulation rate of probiotics,and also facilitated the growth and intestinal adhesion of probiotics,which made the probiotics still had a high survival rate after gastrointestinal digestion.Therefore,the protective effect of W₁/O/W₂emulsion was more conducive for probiotics to play a biological regulatory role in improving intestinal health in inflammatory bowel disease,maintaining the integrity of the intestinal physical barrier,promoting the secretion of tight junction protein,inhibiting the production of pro-inflammatory factors,increasing the content of short chain fatty acids and promoting the growth and reproduction of probiotics.The W₁/O/W₂emulsion could be added to yogurt after fermentation and keep the structure of double emulsion intact,which would not affect the fermentation and flavor of yogurt,but also improved the physical and chemical properties of yogurt.This study established a probiotic delivery system with good physicochemical properties,which could be used to improve intestinal health and provide theoretical basis and technical reference for the development of probiotic functional food.