The effect of a combined pressuretemperature treatment on the structure of blactoglobulin with or wi

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The effect of a combined pressure/temperature
treatment on the structure of b-lactoglobulin
with or without dextran sulfate

• Amar Aouzelleg, Laura-Anne Bull

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High Pressure

• Advantages
• Increased shelf life
• Fresh-like organoleptic qualities
• Nutrients and vitamins unaffected
• Opportunity for new products and functionalities
• Energy efficiency, no pressure gradient

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Disadvantages

• Bacterial spore resistance
• High cost of equipment
• Use of moderate pressure in combination with
  temperature

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Pressure effect on b-lactoglobulin

• Bovine b-lactoglobulin
• Pressure induces aggregation of b-lactoglobulin
  at high concentration
• At low concentration the secondary and tertiary
  structure are quite resistant even at 800-900 MPa
• Effect of the presence of Dextran Sulfate

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Experiments

• Conditions Tris-HCl pH 7, 0.5-5 mg/ml
• Parameters
• Pressure 136-294 MPa
• Temperature 38-62C
• Time 10-30 min.
• Circular dichroism analysis
• near-UV 260-320 nm, far-UV 190-260 nm
• Differential Scanning Calorimetry
• Surface Hydrophobicity

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Experimental design
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Near-UV results-tertiary structure

• Characteristic tyrosine and tryptophan trough
• Progressive loss of dichroism due to the
  tryptophan residue (_at_293 nm)
• Loss of tertiary structure

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Far-UV results - secondary structure

• Characteristic of b-sheet protein
• The amplitude of the spectra is increased
• The minimum shifts from 216 nm to 205 nm
• Increase in the a-helical content of the protein

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Near-UV Circular Dichroism
With Dextran Sulfate
Without Dextran Sulfate
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Differential Scanning Calorimetry
Without Dextran Sulfate
With Dextran Sulfate
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Surface Hydrophobicity
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Discussion

• P/T effect on b-lactoglobulin
• Molten globule state
• Intermediate in protein unfolding/folding
• Increased functionality
• Opportunity for industry
• Effect of Dextran Sulfate
• Potential for increased functionality

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Conclusion and Future work

• Validity of combined treatment
• Different molecular structures obtained
• Possible control of structures obtained
• Sensitising effect of dextran sulfate
• Future work should
• Characterise further these species surface (Infra
  Red)
• Test if functional benefits have been obtained
  (e.g. foaming)