Characterization of Colorants Formed by Non-Enzymatic Browning Reactions of Hydroxycinnamic Acid Derivatives

The browning of plant-based food is commonly understood to result from the enzymatic polymerization of phenolic compounds to pigments, called melanin. However, during the thermal treatment of food, enzymes are deactivated, and non-enzymatic reactions predominate. The extent of the contribution of ph...

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Bibliographic Details
Published in:Molecules (Basel, Switzerland) Switzerland), 2022-11, Vol.27 (21), p.7564
Main Authors: Bork, Leon Valentin, Rohn, Sascha, Kanzler, Clemens
Format: Article
Language:English
Subjects:
4-vinylcatechol
Acids
Analysis
Antioxidants
Browning
Caffeic acid
Caffeoylquinic acid
Cocoa
Coffee
Color
Coloring matter
Coumaric acid
Decarboxylation
electrophilic aromatic substitution
Enzymic browning
Ferulic acid
Food
Free radicals (Chemistry)
Heat treatment
Hydroxycinnamic acid
hydroxycinnamic acids
Investigations
Mass spectrometry
Mass spectroscopy
Melanin
Melanoidin
Melanoidins
NMR
NMR spectroscopy
non-enzymatic browning
Nuclear magnetic resonance
Nuclear magnetic resonance spectroscopy
Oligomers
p-Coumaric acid
Phenolic compounds
Phenols
Pigments
Plant-based foods
Reaction products
Substitution reactions
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Summary:The browning of plant-based food is commonly understood to result from the enzymatic polymerization of phenolic compounds to pigments, called melanin. However, during the thermal treatment of food, enzymes are deactivated, and non-enzymatic reactions predominate. The extent of the contribution of phenolic compounds to these non-enzymatic reactions has been speculated (“melanin-like vs. melanoidin-like”), but the literature is limited. Therefore, the aim of the present study was to investigate the heat-induced reactions of caffeic acid (CA), para-coumaric acid (CS), ferulic acid (FA), hydrocaffeic acid (HC), and 5-O-caffeoylquinic acid (CGA) under dry conditions. The model systems were characterized by color formation, reactant conversion, and antioxidant properties. Reaction products were analyzed by high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy. Decarboxylation could be classified as the driving force for the observed color formation and was significantly impacted by the substitution of the aromatic system. Reaction products were found to contribute to an increase in the antioxidant properties of the model systems. The oligomers described in this study could be incorporated into food melanoidins, contributing to the color and antioxidant properties observed in roasted food rich in phenolic compounds, such as coffee or cocoa.
ISSN:1420-3049
1420-3049
DOI:10.3390/molecules27217564