| Capsaicin is a phytochemical extracted from the fruit of chili peppers and is a source of pungent stimulation.Capsaicin is reported to have physiological effects such as anti-inflammatory,anti-cancer,metabolism regulation,antibacterial,and weight loss,and therefore is a potential ingredient for functional food or health food.However,capsaicin is a strong pungent stimulant and direct administration can cause damage to the mucous membrane of the digestive tract.In addition,capsaicin has a low bioaccessibility due to its poor water solubility.As a result,the wide application of capsaicin in the food industry has been greatly limited.In this study,based on the properties of capsaicin,gastrointestinal controlled-released emulsions have been designed to encapsulate capsaicin aiming at reducing their release in the stomach,thereby avoiding irritation of the gastric mucosa and controlling their release in the intestine,thereby improving their bioaccessibility.Based on this,two gastrointestinal controlled-released emulsions with capsaicin loaded were constructed: capsaicinloaded water-in-oil high internal phase emulsion and capsaicin-loaded water-in-oil-in--water double emulsion.The main findings were as follows.A capsaicin-loaded gastrointestinal controlled-released emulsion was designed using a water-in-oil high internal phase emulsion as a carrier.Based on the p H-driven method,sodium alginate was used as a colloid to stabilize water-dispersible capsaicin as the inner water phase,and beeswax,corn oil and PGPR were used to prepare the oil phase.A stable water-in-oil high internal phase with capsaicin loaded was successfully prepared.The physicochemical properties of the emulsion and its regulation on the release of capsaicin under the gastrointestinal tract were investigated.The microstructures of the samples observed by cryo-SEM revealed that lipid shells formed around the water droplets,possibly due to the presence of beeswax crystals.In addition,a three-dimensional network structure was formed in the inner water phase,and the samples containing capsaicin had a denser network structure.The network structure of the oil shell and the inner phase can synergistically hinder the migration of capsaicin and avoid the leakage of capsaicin during storage as much as possible.After 28 d storage at room temperature,98% of capsaicin remained in the inner water phase.The results of in vitro digestion showed that under simulated oral and gastric digestion,there was hardly any capsaicin leaked into the digestive juice,which could avoid the pungency caused by capsaicin and its irritation to mucous membranes.During the digestion process of the small intestine,due to the small specific surface area of the high internal phase emulsion in contact with digestive enzymes,the sample was digested slowly in the small intestine,which resulted in the continuous slow release of capsaicin.In addition,the bioaccessibility of capsaicin was greatly improved.The water-in-oil high internal phase emulsion can effectively control the release of capsaicin in the oral cavity and stomach,but slowly release in the small intestine.It has been verified by animal experiments that the water-in-oil high internal phase emulsion can siginificantly protect the gastric mucosa of mice from the irritation caused by capsaicin.Intestinal-controlled released water-in-oil high internal phase emulsions were selected to encapsulate capsaicin for further study,which was to investigate the enhancement of its bioavailability in vivo.The results showed that the physiological functions of capsaicin were improved through W/O HIPEs-loaded.The body weight,liver weight,and epididymal fat weight of mice fed with HFD were reduced.Meanwhile,the formation of fat droplets in liver tissue and the enlarge of epididymal adipocytes caused by HFD decreased.The content of ALT、AST and TC in serum were also reduced.In addition,W/O HIPEs encapsulation could protect gastric mucosa from irritation caused by capsaicin.A double emulsion with capsaicin entrapped in the inner water phase was designed,hoping that the oil phase and the outer water phase could synergistically provide a physical barrier,therefore reducing the irritation of capsaicin and avoiding the greasy taste of direct consumption of edible oil-based systems.In order to bring the hydrophobic capsaicin into the inner water phase and obtain a stable double emulsion by increasing the viscosity of the inner phase,capsaicin-dissolved ethanol is used to reduce the polarity of the system,resulting in pectin gelation and capsaicin-loaded ethanol-pectin gelatinous mixtures as internal phase.Microstructural analysis indicated the successful preparation of the double emulsions.The double emulsions containing different pectin concentrations all had high encapsulation efficiency of capsaicin,and the samples did not destabilize after 7d storage at room temperature.The droplet structure of the double emulsion after storage was still maintained as determined by optical microscopy.Moreover,the encapsulation efficiency is still above 75%.The results of in vitro digestion showed that the capsaicin-loaded double emulsion still maintained the structure of double emulsion after being digested in the mouth and stomach,which could provide two-phase isolation for capsaicin and avoid the contact between capsaicin and gastric mucosa.Double emulsion encapsulation significantly improved the bioaccessibility of capsaicin.The evaluation results of animal experiments showed that double emulsion encapsulation can effectively protect mouse gastrointestinal tissue from irritation. |
