Preparation,Characterization and Functional Study of Quinoa Polypeptide Complex with Food Polyphenols
The effects of tea polyphenols(TPs)and antioxidant of bamboo leaves(AOB)on quinoa polypeptides(QPs)properties were investigated.Polyphenols induced structural changes,affected antioxidant and antibacterial properties of the polypeptides.The structural changes of QPs with polyphenols in all the composite samples were studied by Fourier transform infrared and fluorescence spectroscopy.ANS probe was used to analyze the surface hydrophobicity of QPs,par-ticle size and potential were used to characterize the QPs-polyphenol particles.The fluorescence results showed that the intrinsic fluorescence of QPs was quenched and decreased with the increase of the number of polyphenols added,and the maximum emission wavelength was red-shifted.Secondary structure analysis showed that the percentage of β-fold,α-helix and random coil of QPs decreased,while the percentage of β-turn increased in all composite samples.When the ratio of QPs to TPs was 1∶2,the percentages of β-fold,α-spiral,random crimp and β-corner were 43.58％,17.20％,12.92％and 26.30％,respectively.When the ratio of QPs to AOB was 1∶2,the percentages of β-folding,α-helix,random curl-ing and β-corner were 49.60％,14.99％,9.79％and 25.62％,respectively.TPs significantly reduced the surface hy-drophobicity of QPs(P＜0.05),When the ratio of QPs∶TPs was 1∶2,the fluorescence intensity of ANS decreased from 74.131.67AU to 62.141.36AU;but AOB had no significant effect on the surface hydrophobicity of QPs(P＞0.05).In ad-dition,the combination of QPs with TPs or AOB significantly improve the antioxidant activity and inhibitory activity of QPs against Escherichia coli and Staphylococcus aureus(P＜0.05).These findings demonstrate the feasible application of TPs and AOB to improve the functional properties of QPs and the potential use of QPs-polyphenol composites in food ingredients and functional food systems.
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