Elayna Tillman Food Chemistry Spring 2017 Barriers to Market: Polyphenol-Protein Interactions in Rapeseed By Products Image source: https://joerperez.wordpress.com/2013/04/07/canola-oil/ Elayna Tillman Food Chemistry Spring 2017

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

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

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

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

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

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?

Factors that modulate protein-polyphenol interactions 14 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

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

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

Factors that modulate protein-polyphenol interactions 14 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

Factors that modulate protein-polyphenol interactions 14 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

Factors that modulate protein-polyphenol interactions 14 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

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

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: https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwjq77bEqqDTAhVl3IMKHdKrBQkQjRwIBw&url=http%3A%2F%2Fcoolchemistrystuff.yolasite.com%2Fresources%2Fgravimetric%2520analysis_Suh_09.ppt&bvm=bv.152180690,d.cGc&psig=AFQjCNF5Sl8n3hYKU-D2dsBitC6QgzyX2g&ust=1492135075159677 Do you think ammonia is an acid or a base? Ammonia pKa= 38

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

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), 489-502. Wada, S., Tomioka, S., & Moriguchi, I. (1969). Protein bindings. VI. Binding of phenols to bovine serum albumin. Chemical & Pharmaceutical Bulletin, 17(2), 320-323.