Inhibition of Maillard reactions in food systems by plant polyphenols

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandling

  • Hongkai Zhu
Plant polyphenols are natural antioxidants that control the Maillard reaction in foods and beverages. The trapping of ɑ-dicarbonyls using plant polyphenols is a significant pathway that has garnered wide interest in research. This Ph.D. project mainly investigates the effect of both pH and polyphenol structure in the trapping of ɑ-dicarbonyl by polyphenols. Moreover, the reactivity between polyphenols and various carbonyl compounds (ɑ-dicarbonyls, furfural compounds, and Strecker aldehydes) were examined in order to identify potential pathways in controlling the Maillard reaction. First, the reaction kinetics between naringenin (flavonoid compound, rich in citrus) and methylglyoxal (MGO) were determined to be within the pH range of 3.0-8.0 at 37 °C. The apparent second-order rate constant for the reaction of MGO with naringenin increased at a pH above the lowest pKa value for naringenin, however, naringenin did not exhibit reactivity with MGO when pH < 5. Accordingly, naringenin was proposed to trap MGO as a base-catalyzed reaction, where naringenin plays a role in trapping via deprotonation. Second, the reaction kinetics of six polyphenols (trans-resveratrol, naringenin, apigenin, kaempferol, fisetin, and epicatechin) with MGO were investigated at pH 7.4 and 37 °C. Kinetics data was used to simulate the competition between MGO modifying nucleophilic amino acid residues in the protein and their reaction with polyphenols at concentrations relevant to UHT milk. Results revealed that the selected polyphenols effectively inhibit the modification of MGO in nucleophilic amino acid residues of proteins. Considering the solubility and flavour of polyphenols, kaempferol and epicatechin are potential candidates that can be used in UHT milk to inhibit the modification of proteins by MGO.Finally, the reaction kinetics between epicatechin (EC) and Maillard-derived carbon yl compounds (ɑ-dicarbonyls, furfural compounds, and Strecker aldehydes) were determined, and corresponding reaction products were characterized by LC-MS/MS. The stored UHT milk containing 0.1% EC was incubated for 24 h at 37 °C to trace the reaction products of EC with carbonyl compounds. The reaction products formed from the reactions between EC and MGO, glyoxal (GO), 5-(hydroxymethyl)furfural (HMF) and acetaldehyde were discovered in the UHT milk samples. Therefore, EC could trap ɑ-dicarbonyls to inhibit the progress of the Maillard reaction as well as trap HMF and acetaldehyde to reduce the formation of Maillard-derived off-flavours. Accordingly, plant extracts rich in polyphenols could serve as efficient inhibitors of Maillard reaction in foods and beverages, but it is important to consider the molecular structure and solubility of the polyphenols from the plant extracts as well as pH of the food system.
OriginalsprogEngelsk
ForlagDepartment of Food Science, Faculty of Science, University of Copenhagen
StatusUdgivet - 2020

ID: 244526198