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Until now, no effective method has been found to monitor the Maillard reaction process for complex protein hydrolysates. Dynamic changes in the concentration of α-dicarbonyl compounds, fluorescence intensity, and browning degree were investigated during the Maillard reaction of corn protein hydrolysates. When the fluorescence intensity reached the peak, deoxyosones would continue to be increased by ARP's degradation. However, the reaction node with the highest fluorescence intensity coincided with the turning point of the browning reaction, and the subsequent browning rate remarkably increased. Therefore, the change in fluorescence intensity could be used to monitor the degradation of ARP and the formation of browning melanoidin at different stages of the Maillard reaction of complex systems, thus effectively indicating the process of the Maillard reaction. When Maillard reaction intermediates (MRIs) with maximum fluorescent compounds were heated, the most abundant pyrazines were subsequently achieved. However, furan compounds would be progressively increased during the thermal process of MRIs with continuously enhanced browning.

The browning formation and taste enhancement of peptides derived from soybean, peanut, and corn were studied in the light-colored Maillard reaction compared with the deep-colored reaction. The fluorescent compounds, as the browning precursors, were accumulated during the early Maillard reaction of peptides and subsequently degraded into dark substances, which resulted in a higher browning degree of deep-colored Maillard peptides (MPs), especially for the MPs derived from corn peptide. However, the addition of l-cysteine in light-colored Maillard reaction reduced the formation of deoxyosones and short-chain reactive α-dicarbonyls, thereby weakening the generation of fluorescent compounds and inhibited the browning of MPs. Synchronously, the peptides were thermally degraded into small peptides and amino acids, which were consumed less during light-colored thermal reaction due to its shorter reaction time at high temperature compared with deep-colored ones, thus contributing to a stronger saltiness perception of light-colored MPs than deep-colored MPs. Besides, the Maillard reaction products derived from soybean and peanut peptides possessed an obvious "kokumi" taste, making them suitable for enhancing the soup flavors.

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.

Amadori rearrangement product (ARP) derived from proline and glucose was prepared in aqueous medium, and purified by ion exchange chromatography and identified by mass spectrometry and nuclear magnetic resonance spectrometry. The ARP was confirmed as 1-deoxy-1-L-proline-D-fructose (C 11 H 19 O 7 N, 277 Da) with four main isomers. A preliminary vacuum dehydration coupled with subsequent spray drying was used to improve the yield of ARP conversion from 3.63% to 69.15%. Furthermore, the taste characteristics of spray dried ARP products were analyzed by electronic tongue and sensory evaluation. The results indicated that when the dosage of ARP products was above 0.4%, a 20% salt reduction could be achieved without reduction in the salty taste as well as having a significant enhancement in the umami attribute. The products at low- and medium- extents of reaction could stimulate more secretion of aldosterone in oral cavity and then improve its sensitivity to the salt, while the product at high- extent of reaction inhibits aldosterone secretion., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Maillard reaction intermediates (MRIs) derived from enzymatic hydrolysates of pea protein, mainly initial Maillard reaction products, were prepared at a low temperature (80 °C) and the reaction time was determined by variable-temperature Maillard reaction. Electronic tongue and sensory evaluation were used to analyze the taste qualities of pea protein hydrolysates and their MRIs. Both evaluations showed that bitterness of enzymatic hydrolysates of pea protein reduced but umami taste increased through Maillard reaction. The intensities of umami and saltiness were positively correlated with the concentration of MRIs. Even when the dosage of MRIs was 0.1% (w/w), MRIs could achieve a 20% reduction in NaCl content without decreasing saltiness, which could be great potential substitutes for salt reduction. On the other hand, the increased MRIs promoted aldosterone secretion in saliva, which might enhance human perception of saltiness., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Pea protein was used to prepare the Maillard reaction products (MRPs) through enzymatic hydrolysis and further thermal reaction with reducing sugar. A pronounced saltiness improvement in NaCl solution was observed by the addition of hydrolysates and their MRPs. Low-molecular-weight pea peptides had the strongest effect of saltiness and umami enhancement. The saltiness-enhancing effect of MRPs derived from hexoses was higher than that from pentoses. Molecular weight distribution and amino acid content of MRPs prepared under different time revealed that the hydrolysis of peptides and the initial Maillard reaction of hydrolysis products were dominant at 1 h of thermal reaction. With the extension of heating time, further reaction of small tasty peptides led to a decrease in the saltiness enhancement. The kokumi attribute was mainly contributed by the MRPs of small peptides. When the dosage of MRPs was 0.7% coupled with 0.4% NaCl, the saltiness of the solution was higher than that of the control (0.5% NaCl), which meant that the saltiness was not weakened even when the NaCl concentration was reduced by 20%. The results of the electronic tongue analysis were consistent with that of the sensory evaluation. [ABSTRACT FROM AUTHOR]

In order to give the boiled sunflower seeds the rich taste, caramel aroma, and improved oxidation resistance, Maillard peptides were added to sunflower seeds in this research. Sunflower seeds sample 5 (SFS5) and sunflower seeds sample 2 (SFS2) were prepared by adding Maillard peptides of sunflower seeds (K), gluten (G), and corn (Y), at different ratio (SFS2, K:G = 8:2; SFS5, K:G:Y = 8:1:1). Component analysis showed that SFS5 and SFS2 were significantly higher in umami amino acids than the control (SFS0) without Maillard peptides. SFS5 and SFS2 contained more hybrid compounds such as pyrazines and furans which contributed to the caramel aroma of sunflower seeds. Electronic tongue analysis revealed the higher response values of umami, salty, and continuity taste for SFS5 and SFS2 than those of SFS0. Sensory evaluation results showed that the sunflower flavor, caramel aroma, umami characteristic, and overall acceptability of SFS5 and SFS2 were higher than that of SFS0. The chemical results showed that under accelerated oxidation, the SFS5 and SFS2 had significantly lower peroxide value and acid value than SFS0. [ABSTRACT FROM AUTHOR]

Highlights • The flavor of Maillard reaction products (MRPs) solution was unstable during storage. • The size of particles in MRPs increased dramatically after storage or heat treatment. • The Maillard reaction intermediate (MRI) was heat labile but stable during storage. • The heated MRI showed flavor fingerprints as the MRPs before heat treatment. • The MRI has tremendous capacity to be applied as a potential alternative to MRPs. Abstract The Maillard reaction intermediate (MRI) and Maillard reaction products (MRPs) derived from xylose (Xyl) and phenylalanine (Phe) were prepared, then stored at 25 °C for 60 days. After storage, the contents of flavor compounds and the clarity of MRPs solution decreased, and the apparent Z-average hydrodynamic diameter (D h) of particles in the solution increased from 149 to 439 nm. However, the MRI solution remained transparent during storage. The concentration of MRI only decreased by 6.49%, and A 294 of the solution increased slightly yet A 420 remained stable. Numerous flavor compounds in MRPs decreased during heat treatment, meanwhile the cross-linking and aggregation of MRPs were intensified, and the particles’ D h increased to micron level. The heated MRI solution showed a similar appealing profile and flavor fingerprints as the MRPs solution before heat treatment. Controlled formation of flavors from MRIs is proposed to be used as potential alternative to the existing Maillard flavorings. [ABSTRACT FROM AUTHOR]

Maillard reaction products (MRPs) were prepared from mushroom hydrolysate (MH) by heating with d-xylose and l-cysteine at various temperatures (100 °C–140 °C) for 2 h at a pH of 7.4. The sensory characteristics of MH and MRPs were evaluated by panelists and volatile compounds were analyzed by GC/MS. Additionally, partial least squares regression (PLSR) was performed to analyze the correlation between quantitative sensory characteristics and GC/MS data. GC/MS results revealed that higher reaction temperature resulted in more nitrogen and sulfur containing compounds in MRPs while alcohols, ketones and aldehydes were the major flavor compounds obtained in MH. PLSR results showed that 3-phenylfuran and 2-octylfuran were the compounds responsible for the caramel-like flavor; 1-octen-3-ol, (E)-2-octen-1-ol and geranyl acetone were significantly and positively correlated to mushroom-like flavor, whereas, 2-thiophene-carboxaldehyde, 2,5-thiophenedicarboxaldehyde and 3-methylbutanal positively affected MRPs meat-like attribute. Overall, 125 °C was identified as the optimal temperature for preparing MRPs with abundant volatile compounds and favorable sensory characteristics; the concentration of free amino acids and 5′-GMP, which are associated with the umami taste, in MRPs derived under 125 °C were 3 to 4 times higher than those in MH. [ABSTRACT FROM AUTHOR]

[Display omitted] • 1. Microwave intermittent heating can effectively regulate the Maillard reaction process. • 2. The rapid preparation of the Amadori compound (ARP) was realized by microwave heating. • 3. Dehydration rate and microwave effects were key factors to improve the yield of ARP. • 4. ARP can degrade rapidly and accelerate the Maillard reaction in microwave processing. • 5. ARP was expected to be an important color enhancer for microwave fast processed food. Directional and rapid formation of the Amadori rearrangement product (ARP) from the glutamic acid and xylose was achieved through intermittent microwave heating. The yield of ARP reached 58.09 % by subjecting the system to intermittent microwave heating at a power density of 10 W/g for 14 min. Dehydration rate and microwave effects were found to be key factors to optimize the conditions for directional and rapid preparation of the ARP. Through a comprehensive analysis of the ARP degradation and further browning under both conductive and microwave thermal processing, it was observed that microwave processing significantly accelerated the browning degree of systems, leading to a tenfold reduction in the heating time required for browning. This research presented a promising avenue for the development of novel and expedited methods for the production of ARP and highlighted the potential of ARP in enhancing color quality in fast-cooking applications utilizing microwave. [ABSTRACT FROM AUTHOR]