Construction Of High Loading Capacity Diglyceride Oil Microcapsules And Their Loading Properties With Curcumin

Diglycerides is a kind of functional oil equipped with physiological functions that inhibit fat accumulation,prevent systemic inflammatory diseases and promote cardiovascular health.However,poor oxidative stability,low water solubility and low oral availability of liquid diglycerides are drawbacks that limit the availability of diglycerides in food products.To ameliorate the limitations of diglycerides in production applications,this study aims to construct microcapsules with high diacylglycerol oil loading capacity utilizing whey protein isolate(WPI),octenyl succinate amylose(OSA starch)compounded with polydextrose(PD)as the microcapsule wall material,which has both stable properties,and good solubility.Curcumin,a liposoluble active substance with antioxidant and anti-inflammatory physiological functions,can be dissolved in diglyceride oil not only to improve its oxidative stability,but also the two have a synergistic effect in anti-inflammation.Therefore,the application of high loading diglyceride microcapsules in curcumin(CUR)loading delivery was further investigated using high loading diglyceride microcapsules as a carrier,with the following main studies:The binary wall OSA-PD microcapsules were first constructed.The optimum process conditions were as follows: Oil loading of 50%,solids content of 30%,wall OSA starch to PD ratio of 2:1,inlet air temperature of 160°C.Under these conditions,the stability index of the initial emulsion was 80.49% after 28 d of storage at room temperature,and the encapsulation efficiency and yield of the microcapsules were 90.57% and 75.48% respectively.On the basis of binary wall microcapsules,WPI was introduced to prepare ternary wall microcapsules encapsulated with DAG oil in order to further enhance the emulsion stability and encapsulation efficiency.The effect of modulating the compounding ratio between the emulsifiers in the wall material(10:0,9:1,7:3,5:5,3:7,1:9 and 0:10 for WPI and OSA starch respectively)on the physicochemical properties,thermal stability and emulsion properties of the microcapsules after compounding was investigated.Compared with the binary wall microcapsules OSA-PD,the ternary composite wall material microcapsules had high thermal stability of DAG oil inside the microcapsules and the reconstructed emulsions of microcapsules had small average particle size and uniform particle size distribution,indicating that this composite wall material played a good role in protecting the DAG oil inside.Among them,the composite wall material microcapsules WPI-OSA(5:5)-PD with a 5:5 ratio of WPI to OSA starch content performed the most outstandingly with the smallest initial emulsion particle size,the lowest apparent viscosity,the strongest storage stability(with a stability index of 96.90% after 28 d of storage),a smooth microcapsule surface with few folds and cracks after spray drying,the highest encapsulation rate(96.03%)and the highest yield(87.95%),indicating that the microcapsule with this kind of wall material combination had the highest encapsulation capacity.In addition,infrared spectroscopy revealed that the WPI-OSA(5:5)-PD microcapsules had the characteristic infrared band of DAG oil and hydrogen bonding between the walls,which contributed to the increase in solubility(88.25%)and the decrease in wetting time(83.00 s)of the microcapsules,indicating that this is the optimum ratio of emulsifier compounding,under which the microcapsules exhibit excellent processability,stability and rehydration capacity.On this basis,the ability of the microcapsules to load the lipid-soluble active substance curcumin was further investigated using the above-mentioned ternary wall microcapsules as a carrier,and the moisture absorption,storage stability and simulated release properties of the loaded microcapsules were investigated.The results showed that the isotherms of DAG microcapsules were suitable for fitting the GAB model and the WPI-OSA-PD-CUR microcapsules were the least hygroscopic and more conducive to storage.After accelerated oxidative storage,the ternary wall material was the most effective in inhibiting oxidation of the microcapsules during storage.The oxidation reactions of both curcumin-loaded crude oil and ternary wall microcapsules were applied to the zero-level kinetic model,and the shelf life of curcumin-loaded ternary wall microcapsules was 684 d,when stored at 20°C,indicating that the shelf life of DAG oil was extended.Further,the release behavior of the microcapsules was studied by simulating digestion and it was found that the microcapsules were more resistant to gastric digestion,while in the intestine the WPI-OSA-PD microcapsules showed high FFA release,highest curcumin bioavailability,retention and excellent controlled release performance.