Allyl Isothiocyanate Release and the Allelopthic Potential of Brassica Napus
Emulsifying capacity of whey proteins covalently modified ... · • Covalent modification of WPI...
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• Covalent modification of WPI with cabbage compound allyl isothiocyanate (AITC) increases BLG structural flexibility [1,2]. Cleavage of 1 disulfide bridge Binding to 1 free thiol group Emulsifying capacity of whey proteins covalently modified with cabbage compound allyl isothiocyanate Julia K. KEPPLER 1 , Anja STEFFEN-HEINS 1 , Claire BERTON-CARABIN 2 , Karin SCHWARZ 1 1 CAU Kiel, Institute of Human Nutrition and Food Science, Department of Food Technology, Kiel, Germany 2 WU Agrotechnology & Food Sciences, Food Process Engineering Group, Wageningen, The Netherlands [1] Keppler, J.K., Koudelka, T., Palani, K., Stuhldreyer, M.C., Temps, F., Tholey, A., Schwarz, K. (2014) a: Journal of Biomolecular Structure & Dynamics 32(7): 1103-1117. [2]Keppler, J.K., Koudelka, T., Palani, K., Tholey, A., Schwarz, K. (2014) b: Food Biophysics 9(4): 1-10. [3] Frenzel, M.; Steffen-Heins, A. (2015): Food Chemistry, 173: 1090–1099 . Literature Can the changed physicochemical properties and loose conformation of modified BLG increase the emulsifying capacity of WPI at acidic pH values? Proof of a covalent interaction of BLG in WPI: Figure 1: RP-HPLC: Retention time [min] of modified whey proteins (WPI + AITC) shifts to the right in dependence of the added AITC concentration [%]. This also indicates an increased hydrophobicity of the proteins. AITC modification increases WPI hydrophobicity: AITC modification results in a lower interfacial tension than unmodified WPI at o/w interface : Figure 3: Drop tensiometry: modified WPI resulted in a lower equilibrium interfacial tension at oil/water interfaces at pH 2 and 4. Additionally, the viscoelastic modulus was increased for modified WPI – revealing a more dense interfacial layer. AITC modification reduces the emulsion creaming rate: Binding to 3 amine groups AITC modification reduces emulsion oil droplet size at pH 2: Covalent modification of WPI with AITC can increase its hydrophobicity and surface activity. Further results (FTIR, not shown) also confirmed are more loose conformation. Emulsifying capacity of modified WPI was increased at acidic pH. Underlying mechanisms are higher structural flexibility and hydrophobicity, A different alignment at o/w interfaces seems possible. Covalent modification with secondary plant compounds is a promising approach to change protein functionality! Contact: [email protected] Figure 4: Static light scattering: The volume mean oil droplet diameter D [4,3] (μm) was significantly reduced at pH 2, but increased at pH 4. No effect of WPI modification on oil droplet diameter was visible at pH 6 and 7. Figure 6: Analytical centrifugation LUMifuge: The accelerated creaming rate [um/s] at 328 * g was significantly lower for modified WPI at all pH-values tested. Molar ratio of 1:500 (WPI:AITC): n = 5 binding sites. AITC + B-Lactoglobulin pH 2 pH 4 pH 6 pH 7 0 200 400 600 800 1000 Hydrophobicity Index native modified * * * pH 2 pH 4 pH 6 pH 7 0 5 10 15 20 25 Equilibrium interfacial tension (mN/m) native modified ** *** pH 2 pH 4 pH 6 pH 7 0.0 0.2 0.4 0.6 0.8 D [4,3] (μm) native modified * ** pH 2 pH 4 pH 6 pH 7 0.0 0.1 0.2 0.3 0.4 Creaming rate [μm/] native modified * * * * Figure 2: ANS fluorescence: ANS interacts with hydrophobic surface patches on the proteins. This increases the ANS fluorescence. The hydrophobicity index reflects the ANS fluorescence after interacting with native or modified WPI at different pH values. 10 15 20 25 0 100 200 300 1000 1500 Retention Time [min] absorbance [A.U.] WPI WPI + 0.02 AITC WPI + 0.04 AITC WPI + 0.12 AITC -lactalbumin -lactoglobulin A and B -lactalbumin + AITC -lactoglobulin + AITC AITC modification reduces micropolarity-, and viscosity of the protein surface and interface in emulsions: Figure 5: Electron spin resonance: Line shape analysis of the EPR spectrum to distinguish between coexisting spectral domains of the spin probe Tempolbenzoate (TB) in emulsions (a) [3]. Micropolarity by hypersplitting constant a N (b), microviscosity by rotational correlation time c (c) of TB at the protein surface (population 1). (c) (b) lipid phase interface aqueous phase/ protein surface (a) • Emulsifying capacity of ß- lactoglobulin (BLG) rich whey protein isolate (WPI) at acidic pH is strongly reduced. Emulsification: High pressure homogenisation • 400 bar • 3 passes • 18 % rapeseed oil • 1 % WPI • water pH 2, 4, 6 or 7
Transcript of Emulsifying capacity of whey proteins covalently modified ... · • Covalent modification of WPI...
• Covalent modification of WPI with cabbage compound allyl isothiocyanate (AITC) increases BLG structural flexibility [1,2].
Cleavage of 1 disulfide bridge
Binding to 1 free thiol group
Emulsifying capacity of whey proteins covalently modified with cabbage compound allyl isothiocyanate
Julia K. KEPPLER1, Anja STEFFEN-HEINS1, Claire BERTON-CARABIN2, Karin SCHWARZ1
1 CAU Kiel, Institute of Human Nutrition and Food Science, Department of Food Technology, Kiel, Germany 2 WU Agrotechnology & Food Sciences, Food Process Engineering Group, Wageningen, The Netherlands
[1] Keppler, J.K., Koudelka, T., Palani, K., Stuhldreyer, M.C., Temps, F., Tholey, A., Schwarz, K. (2014) a: Journal of Biomolecular Structure & Dynamics 32(7): 1103-1117. [2]Keppler, J.K., Koudelka, T., Palani, K., Tholey, A., Schwarz, K. (2014) b: Food Biophysics 9(4): 1-10. [3] Frenzel, M.; Steffen-Heins, A. (2015): Food Chemistry, 173: 1090–1099 .
Lite
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Can the changed physicochemical properties and loose conformation of modified BLG increase the emulsifying capacity of WPI at acidic pH values?
Proof of a covalent interaction of BLG in WPI:
Figure 1: RP-HPLC: Retention time [min] of modified whey proteins (WPI + AITC) shifts to the right in dependence of the added AITC concentration [%]. This also indicates an increased hydrophobicity of the proteins.
AITC modification increases WPI hydrophobicity:
AITC modification results in a lower interfacial tension than unmodified
WPI at o/w interface :
Figure 3: Drop tensiometry: modified WPI resulted in a lower equilibrium interfacial tension at oil/water interfaces at pH 2 and 4. Additionally, the viscoelastic modulus was increased for modified WPI – revealing a more dense interfacial layer.
AITC modification reduces the emulsion creaming rate:
Binding to 3 amine groups
AITC modification reduces emulsion oil droplet size at pH 2:
Covalent modification of WPI with AITC can increase its hydrophobicity and surface activity.
Further results (FTIR, not shown) also confirmed are more loose conformation.
Emulsifying capacity of modified WPI was increased at acidic pH.
Underlying mechanisms are higher structural flexibility and hydrophobicity, A different alignment at o/w interfaces seems possible.
Covalent modification with secondary plant compounds is a promising approach to change protein functionality!
Contact: [email protected]
Figure 4: Static light scattering: The volume mean oil droplet diameter D [4,3] (µm) was significantly reduced at pH 2, but increased at pH 4. No effect of WPI modification on oil droplet diameter was visible at pH 6 and 7.
Figure 6: Analytical centrifugation LUMifuge: The accelerated creaming rate [um/s] at 328 * g was significantly lower for modified WPI at all pH-values tested.
Molar ratio of 1:500 (WPI:AITC): n = 5 binding sites.
AITC + B-Lactoglobulin
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Figure 2: ANS fluorescence: ANS interacts with hydrophobic surface patches on the proteins. This increases the ANS fluorescence. The hydrophobicity index reflects the ANS fluorescence after interacting with native or modified WPI at different pH values.
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.U.]
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- la c ta lb u m in
- la c to g lo b u lin A a n d B
- la c ta lb u m in +
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- la c to g lo b u lin
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AITC modification reduces micropolarity-, and viscosity of the protein surface and interface in
emulsions:
Figure 5: Electron spin resonance: Line shape analysis of the EPR spectrum to distinguish between coexisting spectral domains of the spin probe Tempolbenzoate (TB) in emulsions (a) [3]. Micropolarity by hypersplitting constant aN (b), microviscosity by rotational correlation time c (c) of TB at the protein surface (population 1).
(c)
(b)
lipid phase
interface
aqueous phase/ protein surface
spin probe: TB
(a)
• Emulsifying capacity of ß-lactoglobulin (BLG) rich whey protein isolate (WPI) at acidic pH is strongly reduced.
Emulsification: High pressure homogenisation • 400 bar • 3 passes • 18 % rapeseed oil • 1 % WPI • water pH 2, 4, 6 or 7
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