1. Elayna Tillman Food Chemistry Spring 2017
Barriers to Market: Polyphenol-Protein Interactions in Rapeseed By Products
Image source:
Elayna Tillman
Food Chemistry
Spring 2017

2. 1. Context – What is the problem? 2. Chemistry – What is the cause?
Presentation Outline
1. Context – What is the problem?
2. Chemistry – What is the cause?
3. Control – How can it be controlled?
4. Review

3. Steam Press Bleach Deodorize Oilseed Cake Byproduct
Background: Oil Processing
Steam
Press
Bleach
Deodorize
Oilseed Cake Byproduct
40% protein
Potential use in formulations
Approximately 2% natural antioxidants
Contributes to undesirable taste and reduces nutritional quality
Note: protein is “well-balanced” for human use (Naczk et al) based on its amino acid composition
Can’t develop a product unless control this problem

4. Hydrogen bonding forms protein-polyphenol association
Mechanism of Effect
complex formation between natural antioxidants (phenolic compounds) and proteins (salivary protein, albumin protein, globulin protein, lipase enzyme, etc.)
Diagram of simple phenol-amino acid complex formation
the amino acid glycine
phenol
Hydrogen bonding forms protein-polyphenol association

5. What is a hydrogen bond?
“Hydrogen bonds are formed when a hydrogen atom covalently bonded to a highly electronegative atom (N, O, and F) is attracted to a nonbonding electron pair on another highly electronegative atom (N, O, or F). The second electronegative atom may be in another molecule, or it may be in the molecule containing the hydrogen atom.” (Bell & Society, 2005)
Point: every Hydrogen atom in molecule can not participate in H-bonding

6. Multiple sites of H-bond formation
Diagram of phenolic acid-amino acid complex formation
Trans-sinapic acid
The most prevalent phenolic compound in rapeseed products

7. Maximum H-bond formation
Diagram of phenolic acid-amino acid complex formation
What do you think these interactions would do to a peptide chain folded into a specific conformation?

8. Factors that modulate protein-polyphenol interactions14
Low [H+]
High pH pH 7
What’s the name of the quantitative measurement that indicates the strength of an acid/base?
High [H+]
Low pH

9. pKa= the pH at which an acid is 50% dissociated and 50% associated
pKa determines how a chemical species responds to change in its equilibrium
LeChatlier’s Principle: A chemical system responds to changes in its environment by shifting to maintain equilibrium (Bell & Society, 2005)
Phenol= 9.95
-COOH group = 2.34
-+NH3= 9.60
pKa 14
association
dissociation

10. Phenol= 9.95
-COOH group = 2.34
-NH3= 9.60
pKa 14
association
dissociation

11. Factors that modulate protein-polyphenol interactions14
Low [H+]
High pH
pKa= 2.34
pKa=9.60
pKa=9.95 pH 7
How would the complex respond to a decrease in pH?
High [H+]
Low pH

12. Factors that modulate protein-polyphenol interactions14
Low [H+]
High pH
pKa= 2.34
pKa=9.60
pKa=9.95 pH 7
Acidic conditions favor complex formation between phenolic acids and amino acids because the Hydrogen atoms remain associated and allow for H-bond formation
High [H+]
Low pH

13. Factors that modulate protein-polyphenol interactions14
Low [H+]
High pH
pKa= 2.34
pKa=9.60
pKa=9.95 pH 7
How would the complex respond to an increase in pH?
E.g. pH=10?
High [H+]
Low pH

14. Basic conditions favor the hydrolysis of the complex
Factors that modulate protein-polyphenol interactions 14
Low [H+]
High pH
pKa= 2.34
pKa=9.60
pKa=9.95 pH 7
Basic conditions favor the hydrolysis of the complex
Application: used to assay the phenolic content in the rapeseed meal
High [H+]
Low pH

15. Batch & Counter Current Extractions - Alcohol and Ammonia
Control by processing
Toasting - Heat treatment stimulates the synthesis of a sinapic acid polymer
Batch & Counter Current Extractions - Alcohol and Ammonia
Filter cake picture:
Do you think ammonia is an acid or a base?
Ammonia pKa= 38

16. Review
The rapeseed plant contains what compound that influences quality?
Phenolics, polyphenolics, phenolic acids
What is one of the sensory attributes of rapeseed byproducts?
Bitterness, astringency
What’s the cause of this organoleptic property?
Protein-polyphenol interaction
What is one of the factors that influences the protein-polyphenol interaction?
pH, acidity/basicity
What is one of the food processing strategies that can eliminate the undesirable sensorial attribute?
Toasting, treatment with NH3, extraction with ethanol

17. References:
Bell, J. A., & Society, A. C. (2005). Chemistry: A Project of the American Chemical Society: W.H. Freeman.
Bruice, P. Y. (2010). Organic chemistry: Prentice Hall.
Naczk, M., Sullivan, A., Amarowicz, R., & Shahidi, F. (1998). Current research developments on polyphenolics of rapeseed/canola: A review. Food chemistry, 62(4),
Wada, S., Tomioka, S., & Moriguchi, I. (1969). Protein bindings. VI. Binding of phenols to bovine serum albumin. Chemical & Pharmaceutical Bulletin, 17(2),