Formation of Fluorescent Maillard Reaction Intermediates of Peptide and Glucose during Thermal Reaction and Its Mechanism

Abstract

The dynamic changes in fluorescence intensity of the Maillard reactions of l-alanyl-l-glutamine (Ala-Gln)/Diglycine (Gly-Gly)/glycyl-l-glutamine (Gly-Gln) and glucose were investigated. It was found that the fluorescence intensity would increase with the reaction time; however, it would decrease after longer heating at higher temperatures, which was accompanied by rapid browning. The strongest intensity occurred at 45, 35, and 35 min at 130 °C for Ala-Gln, Gly-Gly, and Gly-Gln systems, respectively. The simple model reactions of Ala-Gln/Gly-Gly and dicarbonyl compounds were selected to reveal the formation and mechanism of fluorescent Maillard compounds. It was confirmed that both GO and MGO could react with peptides to form fluorescent compounds, especially GO, and this reaction was sensitive to temperature. The mechanism was also verified in the complex Maillard reaction of pea protein enzymatic hydrolysates.

Maillard Reaction Process and Characteristic Volatile Compounds Formed During Secondary Thermal Degradation Monitored via the Change of Fluorescent Compounds in the Reaction of Xylose–Corn Protein Hydrolysate

“…The fluorescence intensity of MRIs generated at various reaction conditions is shown in Figure A–I. Each sample presented a broad fluorescence spectral peak in the range of 410–430 nm, which was consistent with the results of previous studies . As shown in Figure A–D, the fluorescence intensities of MRIs increased slowly with a prolonged reaction time at 50 and 55 °C, and no significant changes ( p < 0.05) in browning intensities were found, indicating that the Maillard reaction was limited at 50 and 55 °C.…”

“…Each sample presented a broad fluorescence spectral peak in the range of 410−430 nm, which was consistent with the results of previous studies. 18 As shown in Figure 1A−D, the fluorescence intensities of MRIs increased slowly with a prolonged reaction time at 50 and 55 °C, and no significant changes (p < 0.05) in browning intensities were found, indicating that the Maillard reaction was limited at 50 and 55 °C. As the temperature adjusted to 60 °C, the fluorescence intensity of MRIs increased significantly with time, while the browning intensity still showed a slower increase trend (Figure 1E,F); according to Pearson's correlation, a strong positive correlation between fluorescence intensity and browning degree was observed (r = 0.966, p < 0.01).…”

“…32,33 This also implied that the consumption of ARP was accelerated during the formation of fluorescent compounds. 18 Therefore, it could be inferred that F1 and F2 contained more ARP than F3−F5. Degradation of ARP promotes the formation of regenerated peptides which could react directly with α-dicarbonyl compounds, leading to the increase of the content and types of the pyrazine compounds.…”

“…Similar to the α-dicarbonyl compounds, the fluorescent compounds have also been demonstrated to be the precursors of browning compounds . Previous studies suggested that the presence of amino acids is necessary for the development of fluorescence. , A recent study by Xia et al proposed that the peptides and α-dicarbonyl compounds that involved in the reaction of the generation of fluorescent compounds showed a gradual accumulation, followed by a fast consumption trend in the model system of peptides and glyoxal/methylglyoxal. However, the specific formation stage of fluorescent compounds during the Maillard reaction of complex peptides remains to be verified.…”

Light-Colored Maillard Peptides: Formation from Reduced Fluorescent Precursors of Browning and Enhancement of Saltiness Perception

“…The yields of 3-DX and GO gradually increased with the extension of reaction time in the deep-colored systems, especially for the latter one (Figure ). Xia et al monitored the reaction of the dipeptide–glucose model and found that short chain α-DCs could react quickly with small peptides to form a large number of fluorescent compounds, which were further converted into browning pigments. However, the production rate of 3-DX and GO in light-colored systems decreased largely, and the content was much lower than that of deep-colored one (Figure ).…”