| With the improvement of living standards,people are increasingly concerned about the nutritional value,health benefits,and functional effects of food.Astaxanthin（ASTA）,known for its potent antioxidant properties,has attracted significant attention as a natural active substance.However,it is insoluble in water and senstive to light,oxygen,and temperature,which limits its practical use.To address this issue,encapsulation technology offers an effective solution for the application of astaxanthin.Zein,as a natural macromolecule,possesses several advantages,including low cost,high safety,and good biocompatibility.It is an excellent carrier for embedding functional substances.Nevertheless,Zein has the problems of poor water solubility and environmental sensitivity.In this paper,pea protein（PP）and Zein were combined by p H cycle method to form hydrophilic complex protein,and pectin（Pec）was introduced for further molecular modification,so as to construct a ternary complex with low environmental sensitivity and explore its formation mechanism.On this basis,the influence of the complex as the carrier of astaxanthin on its embedding effect,stability and oxidation resistance was investigated,which provided a basis for realizing the effective encapsulation of astaxanthin and promoting its application.The effect of the mass ratio of Zein to pea protein on the formation of a binary complex protein（Zein-PP）was investigated and the mechanism of co-assembly between these two proteins was clarified.Through the modification of Zein by pea protein,the solubility was significantly increased.When the mass ratio of Zein/PP was 1:2,the solubility of the complex protein reached 92.61%.Compared with Zein and pea protein,the Zein-PP complex protein exhibited a smaller mean particle size and polydispersity index（PDI）.The results of circular dichroism spectrum,fluorescence spectrum and surface hydrophobicity showed that Zein and pea protein formed a composite structure with hydrophobic groups hidden and hydrophilic groups exposed through protein folding during protonation.The results of dissociation experiment and Fourier transform infrared spectrum confirmed that the main forces forming of Zein-PP were hydrophobic interaction,electrostatic interaction and hydrogen bonding.The effect of pectin modification on the acid sensitivity of Zein-PP complex protein was investigated.Meanwhile,the formation mechanism of ternary complex was explored through fluorescence quenching effect and thermodynamic study The embedding effect of astaxanthin was also evaluated.The results showed that the modification of pectin effectively enhanced the p H stability of the complex protein.It resolved the issues of aggregation and precipitation experienced by the complex protein from p H 4.0 to 5.0 due to its isoelectric point.Fluorescence spectrum,isothermal calorimetry titration and infrared spectrum analysis showed that the modification of complex protein by pectin was a static quenching process under the action of hydrogen bonds,which was a spontaneous exothermic reaction,and the binding constants and binding sites of the two pectins were small.Among them,low-methoxy pectin demonstrated slightly more binding sites with the protein due to its had more carboxyl groups.The binding constant of low-methoxy pectin with the protein was 8.662 mol·L-1,and the number of binding sites was 0.487.Among the complexes with different Zein-PP/Pec mass ratios and different amounts of astaxanthin added,the ternary complex modified by low methoxyl pectin has higher encapsulation efficiency,smaller average particle size（121.23 nm）,PDI（0.246）,and the optimal Zein/PP/Pec mass ratio was 2:4:3,in which the encapsulation efficiency of astaxanthin reached 94.32%.The mechanism of embedding astaxanthin in nanocomposites was further studied,and the environmental stability and antioxidant activity of astaxanthin-loaded ternary complex（ASTA/Zein-PP-Pec）were also investigated.The results of infrared spectrum and X-ray diffraction showed that the embedded astaxanthin was stable in the hydrophobic core of the protein under the action of hydrogen bonds and static electricity,and existed in an amorphous state.Compared with astaxanthin embedded in binary complex protein without pectin modification,ASTA/Zein-PP-Pec had better stability under the conditions of p H 4.0～8.0,high temperature（90°C）,and ultraviolet light（9 h）.The retention rate of astaxanthin was also higher,and a more stable particle size（132.91 nm）,PDI（0.240）,and higher retention rate of astaxanthin rate（87.52%）could be maintained after 15 days of storage.At the same time,the embedded astaxanthin showed better antioxidant activity,and the final release rate in intestinal juice was higher（75.80%）when digested in vitro,which improved its bioavailability... |
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