The Formation Of Curcumin-myofibrillar Protein Complex Under Different NaCl Concentrations Induced By Alkaline Treatment And Its Application

Curcumin,as a natural polyphenol compound,possesses abundant physiological functions such as antioxidant,anti-inflammatory,anti-cancer and anti-bacterial.However,because of its low solubility in water,poor stability and low bioavailability,the application of curcumin in food and pharmaceutical industries is greatly limited.Protein,as a safe,nutritious and convenient delivery carrier,has attracted wide attention for improving the solubility,stability and bioavailability of hydrophobic polyphenols.Meat proteins contain all the essential and non-essential amino acids,which has a very high nutritional value for human.At present,most of the complex formation studies are mainly focused on plant protein and milk protein,there are few studies on meat protein.Therefore,in this study,myofibrillar proteins(MPs)were used as carriers to encapsulate curcumin(hydrophobic polyphenols)to investigate the formation of complex under different NaCl concentrations(0,0.3,0.6,0.9 mol/L)through protein structure changes by pH shifting(12→7).The interaction mechanism between curcumin and MPs and its effect on the oxidative stability of chicken breast were also studied.1、The formation of curcumin-MPs complexes under different NaCl concentrations and their digestive characteristics in vitroA low-cost,convenient,and organic solvent-free approach was investigated to nanoencapsulate curcumin in MPs.The encapsulation was enabled by shifting curcumin-MP mixture to pH 12 and then pH 7 at different NaCl concentrations(0,0.15,0.3,0.6,0.9 mol/L),and confirmed MPs can be as a novel delivery system to promote complex formation.Stable curcumin-MP nanocomplexes were formed at 0.3,0.6 and 0.9 mol/L NaCl,resulting from the exposure of hydrophobic residues of MPs at alkaline pH to bind with dissolved curcumin,which enabled an encapsulation efficiency of about 80%and particle diameters of about 300 nm.The results of in vitro digestion showed,the bioavailability of curcumin and digestibility of MPs were increased after the complex formation between curcumin and MPs,and the secondary and tertiary structures of the complex also changed with the digestion process.2、The interaction mechanism between MPs and curcumin under different NaCl concentrationsThe interaction mechanism between MPs and curcumin under different NaCl concentrations(0,0.3,0.6,0.9 M)was studied.The binding between curcumin and MPs at pH 12 was confirmed by the fluorescence quenching at 0,0.3,0.6 and 0.9 mol/L NaCl.Further kinetic experiments showed,presence of NaCl can against dissociation of curcumin from the protein-polyphenol complex to the aqueous phase.Followed pH shifting from 12 to 7 does not affect UV-Vis absorption spectra of protein-curcumin dispersions.The secondary structure of MPs was not affected by binding with curcumin.Formation of this stable complex can be explained by hydrophobic other than electrostatic interaction.Therefore,the presence of NaCl(0.3,0.6,0.9 M)facilitated exposure of hydrophobic pocket to improve the binding affinity between curcumin and MPs due to the importance of hydrophobic interaction.3.The oxidative stability of curcumin-MPs complex to chicken breastThe effects of curcumin-MPs complex on oxidative stability of chicken breast meat under different NaCl concentrations(0.3,0.6,0.9 M)were studied.DPPH and ABTS free radical scavenging rate experiments showed that the antioxidant activity of curcumin-MPs complexes with pH shifting(12→7)was significantly improved with the increase of NaCl concentration.Further oxidation stability of marinated chicken meats experiments indicated,lipid oxidation and protein oxidation of chicken breast can be greatly inhibited by curcumin-MPs complex during storage at 4℃,and the overall antioxidant capacity of marinated chicken breast can be improved.Therefore,the solubility,stability and bioavailability of curcumin can be effectively improved by MPs through pH shifting(12→7)method.When NaCl concentration was at 0.3,0.6 and 0.9 mol/L,the binding affinity between curcumin and MPs can be greatly enhanced under the action of hydrophobic interaction.Moreover,curcumin-MPs complex can be as a natural oxidative functional material and has potential application in the development of functional meat products.