Based On The Delivery And Emulsification Of Whey Protein To Improve The Bioavailability Of Curcumin

Curcumin, a phenolic compound, is obtained from the dried rhizome of Curcuma longa L. Although curcumin now is widely used as pigment in food processing, it has been shown to exhibit many bioactivities, such as antioxidant, anti-inflammatory and anticancer. Even though it is always possible to extract curcumin through conventional organic solvent methods, the drawbacks of conventional methods are obvious, including the low extraction efficiencies, environmental concerns etc. In addition, curcumin is extremely limited in its application due to its low bioavailability because of its insolubility in water and instability in neutral and alkaline conditions. In this work, three non-conventional extraction methods, the pulsed ultrasonic, microwave and pulsed electric field assisted extraction, were studied to improve the curcumin extraction efficiency. For the purpose to improve curcumin`s bioavailability, bovine β-lactoglobulin was used to form a complex with curcumin and whey protein was used as emulsifier to prepare nanoemulsion. Caco-2cell was cultured to investigate the effect of different delivery systems on absorption for curcumin.In the study of curcumin extraction, the single-factor and response surface experiments were used to obtain the optimum conditions. Moreover, the comparison between pulsed ultrasonic and microwave assisted extraction was performed by the energy consumption, extraction efficiency and purity of curcumin. The results showed that the pulsed ultrasonic-assisted extraction was better than continuous ultrasonic extraction and had the same efficiency as microwave-assisted extraction, but the microwave-assisted extraction had higher purity of curcumin and lower energy comsumption. The optimum conditions of pulsed ultrasonic-assisted extraction were at60%AMP,83%ethanol,3/1(s/s) pulsed duration/interval time and10min irradiation time with mass to solvent ratio of1:200. The total yield of curcuminoids was1.03%±0.02%dry weight. The purities of demethoxy curcumin, bis-(demethoxy) curcumin and curcumin were25,32and43%, respectively. For the microwave-assisted extraction, the optimum performance was achieved at72%ethanol concentration,10%power level with7min of extracion time. The total yield of curcuminoids was1.01%±0.02%dry weight. The purities of demethoxy curcumin, bis-(demethoxy) curcumin and curcumin were23%,27%and50%respectively. The results from the study of β-lactoglobulin/curcumin complex indicate curcumin leads to a partial change in β-lactoglobulin secondary structure when it binds to β-lactoglobulin. In fact, curcumin was bound respectively by two different sites of β-lactoglobulin at pH6.0and pH7.0via hydrophobic interaction. The β-lactoglobulin/curcumin complex was formed by one molecule of β-lactoglobulin combining with one molecule of curcumin. The formation of β-lactoglobulin/curcumin complex would give175.50μg/mL solubilised curcumin per one percentage (g/100mL) complex in water. The solubility of curcumin was substantially increased by15954-fold through the complex. The study on pH stability showed that β-lactoglobulin/curcumin complex and curcumin in complex had a good stability in the pH range of2to8. The thermal stability of β-lactoglobulin was improved through forming the complex with curcumin. The effect of binding on antioxidant activity of curcumin was determined by using ABTS and hydroxyl radical scavenging capacity and total reducing ability. The results showed that the ABTS and hydroxyl radical scavenging capacity of curcumin was reduced by binding with β-lactoglobulin, but the total reducing ability of curcumin was improved.Nanoemulsions stabilized by whey protein isolate were produced successfully. The optimum conditions were:5g/100mL protein concentration,20%oil phase and60MPa homogenization pressure for3cycles. The nanoemulsions prepared by whey protein isolate alone exhibited better stability over ionic strength, thermal treatment and storage. ι-Carrageenan showed no effect on the stability of nanoemulsions over thermal treatment, but it reduced the stability of nanoemulsions at high ionic strength or during storage.In protein hydrolysis experiments, both β-lactoglobulin/curcumin complex and nanoemulsion showed a good stability to pepsin but they were easily hydrolyzed by trypsin. In Caco-2cell permeability experiments, the results revealed that the digested nanoemulsion and β-lactoglobulin/curcumin complex provided curucmin with significantly high Papp, but the intact nanoemulsion and unformulated curcumin had low values of Papp. Digested-diffusion was the major absorption mechanism for curcumin in the nanoemulsion, but both direct diffusion and digested-diffusion may all exist in β-lactoglobulin/curcumin complex. The test of allergenicity showed that the allergenicity of β-lactoglobulin decreased by forming complex with curcumin, and the nanoemulsion also had a lower level of allergenicity than whey protein isolate.