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A series of Amadori compounds of glucose were prepared from glycine (G-ARP), diglycine (DiG-ARP), and triglycine (TriG-ARP), and identified by UPLC-MS/MS and NMR. The formation rate of ARPs was TriG-ARPDiG-ARPG-ARP, and their activation energies were 63.48 kJ/mol (TriG-ARP), 72.84 kJ/mol (DiG-ARP), and 84.76 kJ/mol (G-ARP), respectively, suggesting that ARP was formed more easily from small peptides than from amino acid. Although 1-DG was formed much more difficultly than 3-DG, the same order of the formation of 1-DG, 3-DG, and browning was DiGlyTriGlyGly. It was also confirmed that more methylglyoxal and glyoxal would be formed from small peptides than equimolar amino acids. Compared with free amino acid, ARP, deoxyglycosones, and their secondary degradation products were more easily formed from dipeptide and tripeptide, thereby stronger browning occurred and higher reactivity was exhibited in Maillard reaction of di- or tripeptide.

Methionine (Met) oxidation was observed during thermal degradation of methionine/glucose-derived Amadori rearrangement product (MG-ARP). The effects of oxidized methionine products, methionine sulfoxide (MetSO) and methionine sulfone (MetSO

Compared to the method of aqueous Maillard reaction at atmospheric pressure tandem vacuum concentration, a coupling dehydration method combining spray drying and vacuum drying was used to increase aspartic acid-xylose conversion to the Amadori rearrangement product (ARP). The water activity and moisture states were found as effective indicators to characterize the degree of dehydration of Maillard reaction intermediates and efficient formation of ARP. During the vacuum drying process, the water activity of the product powder decreased significantly. Because the formation of ARP was accompanied by intramolecular dehydration, combining spray drying and vacuum drying increased the proportion of bound water in the vacuum-dried product. Free water was easily dissipated via dehydration, which then converted the immobilized water continuously to free water, and the decreased immobilized water further converted the bound water to immobilized water. The reduction in bound water contributed to the intramolecular dehydration of N-substituted d-xylosamine, which would further be transformed to be the ARP through an intramolecular rearrangement. The yield of ARP was increased from 1.68 to 21.53% after spray drying. The ARP yield was substantially increased up to 77.9% by subsequent vacuum drying.

Background Maillard reaction occurs during food processing and storage and accounts for flavor and browning formation. As significant Maillard reaction intermediates, Amadori rearrangement products (ARPs) are key flavor and browning precursors, and the focus of recent Maillard reaction research. Nowadays, more and more functions of ARPs were found, and their production and application would be expected. Scope and approach This review presents an overview of previously published research on ARP formation and degradation to flavors and melanoidins. The information of ARP preparation and its key role in Maillard flavor and browning regulation is provided. Key findings and conclusions The preparation of ARPs has been attracted due to their importance in food science and application. The preparation of ARPs in aqueous medium via simultaneous dehydration-reaction, as well as natural deep eutectic solvent method, was proposed as green and efficient ways for availability in industrial production. The desirable taste enhancer and flavor precursor, ARPs, have great prospect of application as substitutes of monosodium glutamate and the flavoring of final Maillard reaction products. Controlled formation of process flavor and browning could be achieved by ARP application, which is highly preferred by consumers as indicated by hedonic information that fosters cooking motivation of food consumers. The interaction between ARP and browning inhibitors, and its resulted changes in Maillard reaction pathways and the function of products are proposed to be important scientific research topic. Additionally, flavor and browning formation of ARPs with involvement of additional carbonyl and amino compounds are regarded as significant research trends.

The intervention of cysteine (Cys) on the formation of 2,3-butanedione and pyrazines was evaluated during the thermal processing of the alanine-xylose Amadori compound (AX-ARP). With the involvement of Cys, the competitive formation of 2,3-butanedione and pyrazines was induced. The formation of 2,3-butanedione in the AX-ARP/Cys model was suppressed due to the inhibitory effect of the precursors of 2,3-butanedione like deoxypentosones, while the added Cys in the AX-ARP/Cys model competed with the recovered alanine (Ala) to capture glyoxal and methylglyoxal to make up for the absence of pyrazines in the AX-ARP model at an initial pH value of 7. The content of pyrazines increased from 0 up to 16.48 μg/L (120 °C, 120 min). Exogenous Cys itself showed lower reactivity with 2,3-butanedione through the Strecker degradation reaction; while the pH was increased to 8, the degradative products of Cys were facilitated to consume the residual 2,3-butanedione giving rise to the formation of 2,4,5-trimethylthiazole at 120 °C. It was the degradative products of Cys that accelerated the reaction for consumption of 2,3-butanedione rather than Cys itself. Additionally, the inhibitory effect of Cys on 2,3-butanedione formation was weakened under a basic condition, while the promotional effect on the formation of pyrazines was further boosted. With more Cys participating in the process of AX-ARP thermal degradation, the formation of 2,3-butanedione was further inhibited, while the yields of pyrazines were increased.

The browning inhibition of cysteine on the Maillard reaction of glycine-xylose performed under stepwise increased temperature was investigated. The browning degrees of the final products prepared with cysteine addition at different time points were found dissimilar, and the addition time point of cysteine yielding the lightest browning products was consistent with the time when the glycine-xylose Amadori rearrangement product (GX-ARP) reached its maximum yield. To clarify the reason for browning inhibition caused by cysteine, the evolution of key browning precursors formed in the GX-ARP model with cysteine involved was investigated by HPLC with a diode array detector. The results on the browning degree of the thermal reaction products of GX-ARP with cysteine addition showed great inhibition of α-dicarbonyl generation, which resulted in a significant increase in the activation energy of GX-ARP conversion to browning formation during heat treatment. Strong evidence suggested that the additional cysteine got involved in GX-ARP degradation and reacted with the deoxyosones derived from GX-ARP to yield cyclic 2-threityl-thiazolidine-4-carboxylic acid (TTCA). TTCA formation shunted the degradation of deoxyosones into short-chain α-dicarbonyls, which were important browning precursors, and consequently inhibited the Maillard browning.

The Maillard reaction performed under a stepwise increase of temperature was applied for researching the inhibition of Maillard browning caused by ellagic acid. Ellagic acid was found effective for the inhibition of melanoidin formation in the xylose-glycine Maillard reaction but depended on its dosage and the point of time it was added in the reaction system. The lightest color of the Maillard reaction products was observed when ellagic acid was added at the 90th min, which was the point of time when the Amadori rearrangement product (ARP) developed the most. LC-ESI-MS/MS analysis results showed a significant tendency of the ellagic acid hydrolysis product to react with the predominant intermediate ARP to yield an adduct. The adduct stabilized the ARP and delayed its decomposition and inhibited the downstream reactions toward browning. After the ARP was depleted, ellagic acid also showed an effect on scavenging some short-chain dicarbonyls which contributed to the inhibition of Maillard browning.

The flavor intensity of thermally processed 2‑threityl-thiazolidine-4-carboxylic acid (TTCA) was significantly improved to 1.56 times of that generated from MRPs, but its flavor profile was not as desirable as that of fresh MRPs. The synergistic effect between the additional xylose (Xyl) and elevated temperature was proposed and confirmed via the quantitative analyses of regenerative cysteine (Cys) and fragments of deoxyosones (MGO/GO), which reduced the asynchronism between the formation of released Cys from degraded TTCA and retro-aldolisation products of the intermediate deoxyosones. This synergistic effect further enhanced the Strecker degradation of Cys as well as its thermal degradation and thereby promoted the formation of characteristic flavor substances including sulfur-containing compounds and pyrazines, and the total concentrations of TTCA reaction model reached 205.954 μg/L with additional Xyl at 140 °C. Model reaction systems were employed to verify this hypothesis and the proposed mechanism was further elucidated through isotope labeling technique.

The Amadori rearrangement product derived from xylose-glycylglycine (XGG-ARP) is reactive to be attacked by another glycylglycine to generate a xylose-glycylglycine cross-linking product (XGG-CP) as a secondary product of the ARP. In this research, the role of additional glycylglycine in the XGG-ARP degradation was studied, and the dependence of glycylglycine on temperature was further clarified. The yields of XGG-CP and its degradation products were significantly affected by the molar ratio of glycylglycine to XGG-ARP. At the similar total concentration of reactant XGG-ARP and glycylglycine, the yields of XGG-CP, 3-deoxyxylosone, and furfural were dramatically decreased as the molar ratio of glycylglycine to XGG-ARP was increased. However, when the reaction temperature was increased to 120 °C, the increased additional glycylglycine percentage showed an obvious catalytic effect on the XGG-ARP degradation to deoxyosone and thus improved the furfural yield as well. The results revealed that an increased glycylglycine dosage level enhanced both the conversion of XGG-ARP to XGG-CP and the conversion of XGG-CP to 3-deoxyosone. The high-temperature-induced unequal acceleration for XGG-CP formation and degradation at a high glycylglycine dosage further led to a catalytic effect on the ARP degradation to deoxyosone. The concentration of 3-deoxyosone was increased by 37.5% when the molar ratio of glycylglycine to XGG-ARP increased from 1:2 to 2:1 at a temperature of 120 °C.

The effect of additional dl-methionine (Met) on the thermal degradation of a methionine-glucose-derived Amadori rearrangement product (MG-ARP) was investigated under different reaction conditions. The resulting color formation and changes in the concentrations of MG-ARP, Met, and α-dicarbonyl compounds were investigated. Additional Met did not affect the degradation rate of MG-ARP but got involved in subsequent reactions and resulted in a decrease in the contents of C6-α-dicarbonyl compounds. During MG-ARP degradation, the formation of glyoxal (GO) and methylglyoxal (MGO) was facilitated by additional Met, through retro-aldolization reaction of C6-α-dicarbonyl compounds. This effect of Met addition was dependent on the reaction temperature, and the consistent conclusion could be made in a buffer system. The improvement of GO and MGO formation as color precursors caused by the additional Met contributed to the acceleration of browning formation.

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.

Ceramic dish cooking method (CDCM) and microwave absorption dish cooking method (MADCM) were used to obtain one-step microwave-cooked Kung Pao Chicken. Processing the optimization of recipes, steaming time and microwave time was conducted for microwave cooking methods. CDCM showed higher taste scores, better umami and sweet attributes, and better color and aroma than MADCM. The NMR and FITC fluorescence analysis results indicated that free water in chicken cooked by CDCM was lost more and tends to shift to immobilized water during the microwave heating as compared with MADCM. However, the aroma intensity by CDCM was weaker than the traditional cooking method (TCM). Electronic nose analysis also showed difference in the flavor profile from CDCM and TCM. According to the GC-MS analysis, aldehydes, the oxidation products of fats, were higher from TCM than from other cooking methods. Therefore, enzymatic hydrolyzed chicken fat at 5 g per 150 g chicken with a degree of enzymatic hydrolysis of 17.00% was used in CDCM to produce ideal fatty and meaty flavor. Both fatty and meaty flavor have increased by 52% and 60% respectively, with less off-flavor, thus, obtaining a similarity of 92% compared to TCM and with appropriate contents of volatiles such as hexanal, heptanal, (E)-2-octenal, (E)-2-decenal, (E)-2-nonenal and 2,4-decadienal.

This work aimed to investigate the encapsulation and stabilization mechanism of cinnamaldehyde and eugenol in high internal phase Pickering emulsions (HIPPEs) through regulating their interfacial rheological properties and interfacial microstructure. With the incorporation of cinnamaldehyde, the Schiff base reaction between the cinnamaldehyde and proteins favored the formation of the predominantly elastic and solid-like interfacial layers. In contrast, the hydrogen bonds between eugenol and proteins resulted in the transformation of interfacial layers to viscous dominant with weak viscoelastic responses. Thus, cinnamaldehyde-loaded HIPPEs had a better storage stability than eugenol-loaded HIPPEs, and the retention rate was increased by about 15 %∼20 %. The addition of tea camellia seed oil inhibited the mobility of immobilized water and improved the retention rates of cinnamaldehyde and eugenol by approximately 6 % and 12 % (30 days at 25 °C), respectively. These findings will be beneficial for the development and design of effective essential oil encapsulation systems in the food industry.

Industrial production, environmental monitoring, and clinical medicine put forward urgent demands for high-performance gas sensors. Two-dimensional (2D) materials are regarded as promising gas-sensing materials owing to their large surface-to-volume ratio, high surface activity, and abundant surface-active sites. However, it is still challenging to achieve facilely prepared materials with high sensitivity, fast response, full recovery, and robustness in harsh environments for gas sensing. Here, a combination of experiments and density functional theory (DFT) calculations is performed to explore the application of tellurene in gas sensors. The prepared tellurene nanoflakes via facile liquid-phase exfoliation show an excellent response to NO2 (25 ppb, 201.8% and 150 ppb, 264.3%) and an ultralow theory detection limit (DL) of 0.214 ppb at room temperature, which is excellent compared to that of most reported 2D materials. Furthermore, tellurene sensors present a fast response (25 ppb, 83 s and 100 ppb, 26 s) and recovery (25 ppb, 458 s and 100 ppb, 290 s). The DFT calculations further clarify the reasons for enhanced electrical conductivity after NO2 adsorption because of the interfacial electron transfer from tellurene to NO2, revealing an underlying explanation for tellurene-based gas sensors. These results indicate that tellurene is eminently promising for detecting NO2 with superior sensitivity, favorable selectivity, an ultralow DL, fast response-recovery, and high stability.

The interaction mechanism of (-)-epigallocatechin gallate (EGCG) with Amadori compound (Amadori rearrangement product, ARP) in xylose-alanine model reaction systems was investigated. The adducts between ARP and EGCG were identified as two ARP-EGCG isomers, two ARP-EGCG-H

(-)-Epigallocatechin gallate (EGCG) had a significant effect on Maillard reaction intermediate formation in the xylose/alanine model system. A trapping effect of EGCG on the reactive deoxyosones was observed to change the reaction pathways. The rate constant of Amadori rearrangement product (ARP) conversion to deoxyosones was decreased with EGCG addition, indicating an inhibition of ARP degradation. Dehydration improved the ARP formation during the thermal reaction and synergistically improved the yield of ARP with the EGCG trapping effect on the deoxyosones. Additionally, EGCG decreased the activation energy for the conversion of xylose/alanine to ARP (from 77.8 to 62.8 kJ/mol) and in turn accelerated the ARP formation. The effect of EGCG was further facilitated at the optimal conditions of 90 °C, at pH 7.5, and a molar ratio of xylose to alanine of 2:1, which improved the yield of ARP (N-(1-deoxy-d-xylulos-1-yl)alanine) from 2 to 95%.

Photocatalytic water splitting, as an artificial photosynthesis process for producing clean hydrogen energy, has recently attracted extensive attention due to its bright prospects for solving the shortage of fossil energy and environmental crisis. However, it is still challenging to achieve highly efficient overall water splitting because of the unsuitable electronic structure and the strong dependence on the noble metal co-catalysts to date. The development of photocatalytic water splitting is therefore immensely urgent to enlarge the uptake of photocatalysts by exploring novel compounds. Herein, we propose a novel two-dimensional (2D) pentagonal SiAs2 (penta-SiAs2) photocatalyst suitable for water splitting based on first-principles calculations. Using a hybrid functional, we demonstrate the bandgap of 2D penta-SiAs2 to be 2.35 eV, and its band-edges perfectly stride the redox potential of water. Most importantly, this material possesses both highly desirable carrier mobilities and strong light absorption in the visible and ultraviolet (UV) regions, which are superior to those of most previously reported 2D materials. Furthermore, the free energies suggest that hydrogen and oxygen evolution reactions are feasible with penta-SiAs2. These extraordinary characteristics make penta-SiAs2 a promising 2D material for photocatalytic water splitting and provide a possible route for the future experiment scheme.

The Amadori compound of glucose and l-alanyl-l-glutamine (Ala-Gln-ARP) was prepared and characterized by UPLC-MS/MS and NMR. There were no pyrazines produced by heated Ala-Gln-ARP alone due to the asynchronicity of regenerated l-alanyl-l-glutamine and α-dicarbonyl compounds. High temperature (130 °C) and long reaction time could facilitate the 2,5-dimethylpyrazine formation at a small concentration (33.4 ± 3.47 μg/L). The exogenous amino substrates would lower the formation temperature of pyrazines and make it to be generated effectively. Extra supplied l-alanyl-l-glutamine could generate 2,5-dimethylpyrazine at 110 °C, while higher temperature of 140 °C could strengthen the formation of 2,5-dimethylpyrazine (793 ± 119 μg/L) and stimulate the generation of other pyrazines, including methylpyrazine and 2,6-dimethylpyrazine. The exogenous alanine, glutamic acid, and glutamine was also beneficial to enhance the pyrazines formation, especially the glutamic acid. Furthermore, alkaline pH of thermal reaction made pyrazines increase significantly than in neutral medium and further enriched their species such as unsubstituted pyrazine and trimethylpyrazine.

Maillard reaction intermediates (MRIs) derived from enzymatic hydrolysates of soybean protein were prepared by combining dehydration method with spray drying and vacuum drying. Taste characteristics, browning precursors, water activity, and moisture state were monitored during the process of vacuum drying. The water activity was significantly reduced and the proportion of bound water was increased, which could promote the large accumulation of MRIs. The saltiness, umami, and bitterness responses of MRIs were all reduced and the reduction of taste intensity during vacuum drying was probably caused by the reaction of small peptides of taste-active amino acids with glucose. The continuous accumulation of browning precursors during vacuum drying was confirmed by fluorescence spectroscopic analysis and by quantitative analysis of α-dicarbonyl compounds. Subsequent browning reactions further demonstrated that the MRI with the highest fluorescence intensity also had the greatest browning potential.

Compared to the method of aqueous Maillard reaction at atmospheric pressure tandem vacuum concentration, a coupling dehydration method combining spray drying and vacuum drying was used to increase aspartic acid-xylose conversion to the Amadori rearrangement product (ARP). The water activity and moisture states were found as effective indicators to characterize the degree of dehydration of Maillard reaction intermediates and efficient formation of ARP. During the vacuum drying process, the water activity of the product powder decreased significantly. Because the formation of ARP was accompanied by intramolecular dehydration, combining spray drying and vacuum drying increased the proportion of bound water in the vacuum-dried product. Free water was easily dissipated via dehydration, which then converted the immobilized water continuously to free water, and the decreased immobilized water further converted the bound water to immobilized water. The reduction in bound water contributed to the intramolecular dehydration of N-substituted d-xylosamine, which would further be transformed to be the ARP through an intramolecular rearrangement. The yield of ARP was increased from 1.68 to 21.53% after spray drying. The ARP yield was substantially increased up to 77.9% by subsequent vacuum drying.

2-Threityl-thiazolidine-4-carboxylic acid (TTCA), a nonvolatile precursor of flavor and color, is considered to be more stable than its isomeric Amadori compound (ARP). The degradation behavior of TTCA favors higher temperatures and pH. In order to adjust and control the thermal degradation of TTCA to improve its food processing adaptability, a TTCA-Xyl thermal reaction model was constructed to explore the effect of extra-added Xyl on the thermal degradation behavior of TTCA. The results confirmed that the extra-added Xyl was involved in the degradation pathway of TTCA and accelerated its depletion, thus promoting the formation of characteristic downstream products of TTCA including some α-dicarbonyl compounds, and consequently accelerating the browning formation. The isotope-labeling technique was further applied to confirm that the added Xyl could trap the Cys released from the decomposition of ARP and formed additional TTCA, which could promote the movement of chemical equilibrium and gradually accelerate the degradation rate of TTCA as well as melanoidins formation. The higher pH value could even promote this phenomenon.

Maillard reaction intermediate (MGX) generated from glutathione and xylose in aqueous medium was prepared via the Maillard reaction performed under a two-stage temperature increase process. The purified MGX was identified by Fourier-transform infrared spectroscopy, mass spectrometry, and nuclear magnetic resonance as N-(1-deoxy-d-xylulos-1-yl)-glutathione (Amadori compound, C15 H25 O10 N3 S) with five main isomers. The method of Maillard reaction performed under a two-stage temperature increase process was further verified by high-performance liquid chromatography. The optimal reaction time and temperature for the preparation of MGX was determined as 60 min at 90 °C. The yield of MGX was increased from 8.60% to 55.52% through thermal reaction coupled with vacuum dehydration. In addition, rapid and more Maillard-type volatile compounds were formed in MGX during thermal treatment than that in Maillard reaction products or glutathione-xylose mixture. Beside, MGX possessed more pleasing meat-like volatile profile compared with the Amadori compound of glutamic acid-xylose (AAX), cysteine-xylose (ACX), and glycine-xylose (AGX). Therefore, it suggested that the MGX had the potential to achieve a better flavor formation during thermal treatment. PRACTICAL APPLICATION: Maillard reaction intermediates, such as Amadori or Heyns rearrangement products (ARP or HRP), are important flavor precursors, which possess stable physicochemical properties, but tend to degrade into flavor compounds at high temperatures. Maillard reaction intermediate from glutathione and xylose acts as primary flavor enhancers to complete Maillard reaction to produce flavors in the subsequent thermal processing, which can significantly improve and stabilize the flavor quality of the meaty food, and deserves a very broad application prospects. The new developed method will be a significant theoretical basis on research preparation and properties of Maillard reaction intermediates in complex food systems.

The sensing performances of SF6 decompositions, including HF, SOF2, SO2, SO2F2, and H2S, adsorption on monolayer tellurene have been investigated by means of density functional theory (DFT) calculations in this letter. The attained results show that the monolayer tellurene is preferable for SF6 decomposition components, especially for SO2 and SOF2, exhibiting favorable adsorption strength and apparent charge transfers. Besides, the calculated density of states (DOS) further reveals the electronic properties are obviously changed after SO2 and SOF2 adsorption. These results signify that tellurene-based gas sensor is a potential candidate for detecting SF6 decompositions in high-voltage insulation equipment.

The two-dimensional (2D) materials offer tremendous opportunities for efficient, ultrathin solar cells beyond conventional three-dimensional materials. In this work, we study the interfacial electrical properties and charge transfer characteristics of the SiAs2/GeP2 heterostructure by first-principles calculations. The SiAs2/GeP2 heterostructure shows a 2.25 eV bandgap and pronounced solar light absorption. Furthermore, the heterostructure presents a type-II alignment, and possesses a desirable power conversion efficiency (PCE) of up to 12.1%. These results reveal that SiAs2/GeP2 is promising for solar energy conversion in photovoltaic applications, and also provide a possible alternative for experiment scheme.

The effect of simultaneous dehydration-reaction (SDR) on Amadori rearrangement product (ARP) N-(1-deoxy-d-xylulos-1-yl)-glutathione and its key degradation products, 3-deoxyxylosone (3-DX) and 1-deoxyxylosone (1-DX), were investigated in an aqueous glutathione-xylose (GSH-Xyl) system. The yield of ARP was increased to 67.98% by SDR compared with 8.44% by atmospheric thermal reaction at 80 °C. Reaction kinetics was applied to analyze the mechanism and characteristics of ARP formation and degradation under SDR. ARP formation and degradation rate was highly dependent on temperature, and the latter was more sensitive to temperature. By regulating the reaction conditions of temperature and pH, the ratio of ARP formation rate constant to its degradation rate constant could be controlled to achieve an efficient preparation of ARP from GSH-Xyl Maillard reaction through SDR.

Amadori rearrangement product (ARP) derived from glutamic acid (Glu) and xylose (Xyl) was prepared by aqueous Maillard reaction. Subsequently, ion exchange chromatography, MS, and NMR were used for purification and identification, confirming that the molecular formula of ARP was C10 H17 NO8 , namely N-(1-deoxy-α-D-xylulos-1-yl)-glutamic acid, with a molecular mass of 279 Da. To improve the aqueous yield of ARP, a thermal reaction coupled with vacuum dehydration was used and the yield of ARP was increased from 2.07% to 75.11%. Furthermore, flavor formation capacity of ARP by a thermal treatment simulated to a baking process was compared with Maillard reaction products, Maillard-dehydration reaction products, and Glu-Xyl mixture. The results indicated that a larger amount of volatile flavor compounds and a biscuit-like, burnt aroma was generated rapidly from the mixture of ARP and unreacted Glu-Xyl, which could be a potential flavor enhancer for baked foods. PRACTICAL APPLICATION: Maillard reaction performed in aqueous medium through thermal reaction combined with vacuum dehydration is a novel and practical technology that could be widely used to produce Maillard reaction intermediates (MRIs), such as Amadori or Heyns rearrangement products, which are regarded as significant nonvolatile aroma precursors and have stable physical and chemical properties compared with Maillard reaction products (MRPs). MRI derived from glutamic acid and xylose is a potential substitute of MRPs for flavorings preparation and shows a great capacity to generate fresh flavors in a short time at high temperature, which meets the requirements of baking foods. Therefore, the new developed method could be a promising tool for MRI preparation and application in food and flavoring industries.

The Maillard reaction end-products (MRPs) and intermediate (MRI, N-(1-deoxy-α-D-xylulos-1-yl)-phenylalanine) derived from xylose (Xyl) and phenylalanine (Phe) model system were synthesized in an aqueous medium, and their antioxidant activity was evaluated. Both the MRPs and N-(1-deoxy-α-d-xylulos-1-yl)-phenylalanine exhibited the Fe2+ chelating activity at their addition concentration of 2 to 12 mg/mL. While their reducing power, free radical scavenging activity, and inhibition effect on lipid peroxidation were observed at a lower addition concentration of only 0.2 to 1.2 mg/mL. The free radical scavenging activity was improved with the increase in their concentration, and a time-dependent scavenging effect of the MRI was also shown in the results. However, a weak chelating activity of Xyl-Phe on Fe2+ in a concentration-dependent manner was observed, but no significant free radical scavenging activity or reducing power of Xyl-Phe was found. Based on these results, possible free radical scavenging pathway of the MRI was proposed. As the MRI showed lower antioxidant activity than MRPs, the application of the MRI in combination with MRPs as an antioxidant was proposed in cooked or semi-processed foods to avoid the deterioration induced by oxidation. PRACTICAL APPLICATION: The Maillard reaction intermediates (MRIs) showed antioxidant activity and could be applied in foods as both antioxidants and flavor enhancer. The MRIs will probably extend the shelf-life of lipid rich foods and could be the substitute of artificial antioxidants.; © 2019 Institute of Food Technologists®.

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.

The formation conditions of the Amadori compound (ARP) N-(1-deoxy-d-xylulos-1-yl)-alanine were determined in an aqueous Maillard reaction between l-alanine and d-xylose under a two-step temperature rising process with (-)-epigallocatechin gallate (EGCG) as an indicator followed by browning intensity detection of the final Maillard reaction products (MRPs). To clarify the mechanism of EGCG indication on the ARP formation, the change in the concentration of some key products generated during the Maillard reaction with EGCG addition was investigated. Results showed an inhibition effect of EGCG on the browning precursor formation through the generation of ARP-EGCG adducts and deoxyosone-EGCG adducts, which was proposed as an important pathway to inhibit browning during the Maillard reaction and to indicate ARP formation.

To further explore the aroma mechanism of Chinese faint-scent cigarettes, the contribution of tobacco leaf composition, including six kinds of saccharides, eight tobacco alkaloids, seventeen kinds of organic acids, eighteen kinds of amino acids and four ions (Na+, K+, Mg2+ and Ca2+), on aroma quality characteristic (freshness, flowery and acidic notes) of faint-scent cigarettes was analyzed by chromatography and PLSR. The results showed that (i) xylose, fructose, glucose, maltose and sucrose were negatively correlated to acidic note, while galactose showed significantly positive correlation to acidic note. (ii) Phenylalanine and proline showed significant and positive correlation with characteristic aromas. Proline contributed to freshness and flowery, while leucine significantly contributed to acidic note. (iii) Most organic acids were significantly correlated to characteristic aromas. Palmitic acid and stearic acid contributed to the freshness, while dodecanoic acid and palmitic acid significantly contributed to flowery. (iv) Tobacco Na ion plays negative and significant correlation to acidic note.

The generation of pyrazines in a binary methionine/glucose (Met/Glc) mixture and corresponding methionine/glucose-derived Amadori rearrangement product (MG-ARP) was studied. Quantitative analyses of pyrazines and methional revealed that MG-ARP generated more methional compared to Met/Glc, whereas lower content and fewer species of pyrazines were observed in the MG-ARP model. Comparing the availability of α-dicarbonyl compounds generated from the Met/Glc model, methylglyoxal (MGO) was a considerably effective α-dicarbonyl compound for the formation of pyrazines during MG-ARP degradation, but glyoxal (GO) produced from MG-ARP did not effectively participate in the corresponding formation of pyrazines due to the asynchrony on the formation of GO and recovered Met. Diacetyl (DA) content was not high enough to form corresponding pyrazines in the MG-ARP model. The insufficient interaction of precursors and rapid drops in pH limited the formation of pyrazines during MG-ARP degradation. Increasing reaction temperature could reduce the negative inhibitory effect by promoting the content of precursors.

The effect of additional dl-methionine (Met) on the thermal degradation of a methionine-glucose-derived Amadori rearrangement product (MG-ARP) was investigated under different reaction conditions. The resulting color formation and changes in the concentrations of MG-ARP, Met, and α-dicarbonyl compounds were investigated. Additional Met did not affect the degradation rate of MG-ARP but got involved in subsequent reactions and resulted in a decrease in the contents of C

A two-step emulsification prior to complex coacervation was employed to develop a co-encapsulation technology of hydrophilic and hydrophobic components for nutrition enhancement. Processing parameters of mononuclear ellipse-like microcapsules using gelatin and sodium carboxymethyl cellulose as wall materials were evaluated. The particle size and morphology of microcapsules and the encapsulation efficiency of L-ascorbic acid were significantly affected by the water–oil phase ratio and total biopolymer concentration. The L-ascorbic acid and quercetin co-encapsulated microcapsules with an average size of 65.26 µm showed good physical and chemical stability. The encapsulation efficiencies of L-ascorbic acid and quercetin were 69.91% and 88.21%, respectively. To predict the potential of functional lipids as hydrophobic carriers, microcapsules using soybean oil, olive oil, fish oil, and conjugated linoleic acid as interlayer oils were developed. The encapsulation efficiencies of hydrophobic compounds carried by different oils were similarly high (88.21–93.08%), whereas, hydrophilic ones carried by conjugated linoleic acid had the lowest encapsulation efficiency (32.54%). The interface tension results indicated that the interfacial stability was impaired by a competitive relation between conjugated linoleic acid and hydrophobic emulsifier at the interface, due to their structural similarity. These results provided the guidance for improving the quality of interlayer oils from microcapsules.