ABSTRACT
There is fast increasing interest in the development of alimentary protein stabilized emulsions due to their potential applications in functional food fields. This work studied the effect of glycation degree with chitosan oligosaccharide (COS) on the emulsifying properties of lactoferrin (LF) through Maillard reaction. In the present study, SDS-PAGE and FT-IR were used to confirm LF and COS covalently binding together successfully. Intrinsic fluorescence showed that glycation with COS led more hydrophobic groups exposed to the surface of the structure and particle size increase of LF. Emulsions with 50% (v/v) oil phase and protein concentration of 2% (w/v) was fabricated through one-step shear method. Compared with native LF, emulsions stabilized by LF-COS conjugates showed smaller droplet size and lower creaming index (CI). Among these samples, LF-COS conjugates under 4 h had the best emulsifying efficiency and stability, the emulsion droplet size and the CI of which decreased 39.66% and 28.55% compared with LF, respectively. Furthermore, glycation with COS enhanced the interfacial activity of LF leading to more adsorbing amount and forming thicker layer on the droplets and gel network in the emulsions. This finding would make sense to further understand the modification of emulsifying properties of alimentary proteins through glycosylation with saccharides and develop novel protein-based emulsifiers.
Subject(s)
Chitosan , Lactoferrin , Chitosan/chemistry , Emulsifying Agents/chemistry , Emulsions/chemistry , Glycosylation , Lactoferrin/chemistry , Oligosaccharides/chemistry , Particle Size , Spectroscopy, Fourier Transform InfraredABSTRACT
Glycosylation has a great effect on the antioxidant ability of proteins, which is due to the structural conformational change of peptides in the protein. In this study, a chitosan oligosaccharide (COS) was selected as the saccharide for glycation with lactoferrin (LF) by a wet-heat method, and a new stripe at a higher molecular zone in the gel of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and a change in the bond revealed by Fourier transform infrared (FT-IR) and fluorescence spectroscopy analyses were used to confirm that the chitosan oligosaccharide was successfully covalently bound to lactoferrin. The ABTS and oxygen radical absorbance capacity (ORAC) assays indicated that lactoferrin exhibited a stronger antioxidant activity after glycation with the chitosan oligosaccharide. High-resolution mass spectroscopy further illuminated the relationship of enhanced antioxidant capacity and structural conformational change of peptides in lactoferrin at a molecular level.
Subject(s)
Antioxidants/chemistry , Chitosan/chemistry , Lactoferrin/chemistry , Oligosaccharides/chemistry , Antioxidants/metabolism , Chitosan/metabolism , Electrophoresis, Polyacrylamide Gel , Glycosylation , Lactoferrin/metabolism , Mass Spectrometry/methods , Oligosaccharides/metabolism , Oxygen Radical Absorbance Capacity , Peptides , Spectrometry, Fluorescence , Spectroscopy, Fourier Transform InfraredABSTRACT
The functional properties and physiological functions of whey protein isolate (WPI) decreased near its isoelectric point (PI). The Maillard reaction covalently binding polysaccharides to proteins is an effective method to improve the functional activities of proteins. WPI-inulin conjugates were prepared by wet-heating method at 70 °C for 2 h, 4 h and 6 h, respectively. New bonds at higher molecular zone appearing at SDS-PAGE, decreased free amino acid content and new formed CN bonds in FT-IR of conjugates compared with WPI confirmed the formation of the covalent bonds between WPI and inulin. As the increase of the reaction time, both the brown intensity and fluorescence intensity of WPI-inulin conjugates became higher. Amino acid contents, Circular dichroism analysis and SEM analysis presented the primary structure, secondary structure and surface structure change of protein after covalent with inulin. Emulsion properties of emulsion activity (EAI) and emulsion stability (ES) of WPI-inulin conjugates were assessed and both showed significantly enhanced compared with WPI at range of pH 3 to pH 7. AAPH+ scavenging test and ORAC measurement also revealed that covalent binding with inulin enhanced the antioxidant activities of WPI. This work presented the conjugation with inulin successfully enhanced the functional properties of WPI.
