Mechanism of pyrazines and thioethers formation promoted by high oxygen concentration in the methionine-glucose Maillard reaction system.

Background: The typical aroma compounds in methionine-glucose Maillard products often undergo further degradation and polymerization during storage and thermal processing, leading to flavor dispersion and aroma distortion. It is crucial to identify measures that enhance typical aroma substances in such flavor matrices.

Results: The effect of oxygen on the flavor formation of methionine-glucose thermal reaction system was explored by determining typical flavor substance contents and flavor differences.

Promoted formation of pyrazines by targeted precursor addition to improve aroma of thermally processed methionine-glucose Amadori compound.

The methionine/glucose (Met/Glc) and methionine/glucose-derived Amadori rearrangement product (MG-ARP) models were established to analyze their differences in flavor profiles and aroma potentiality. The principal component analysis revealed the advantage of MG-ARP in the formation of low temperature-induced processing flavor. MG-ARP exhibited superior potential in the rapid formation and high intensity of processed flavor than the Met/Glc except for the inefficiency in pyrazine production.

Control Formation of Furans and Pyrazines Resulting from Dual Glycation Sites in ,-Di(1-deoxy-d-xylulos-1-yl)lysine via Elevating Thermal Degradation Temperatures.

Lysine (Lys) glycated by xylose (Xyl) at α-NH [(1-deoxy-D-xylulos-1-yl)lysine (-Xyl-Lys ARP)] or ε-NH [-(1-deoxy-D-xylulos-1-yl)lysine (-Xyl-Lys ARP)] significantly impacted the thermal degradation pathways of Amadori rearrangement products (ARPs). -Xyl-Lys ARP was found to undergo retro-aldolization on the sugar fragment more readily to form glyoxal/methylglyoxal than -Xyl-Lys ARP. Furans and pyrazines formation during the degradation of the diglycated lysine [,-di(1-deoxy-d-xylulos-1-yl)lysine (-di-Xyl-Lys ARP)] was delayed at 120 °C relative to -Xyl-Lys ARP.

Fabrication and characterization of long-lasting antifungal film containing cinnamaldehyde-loaded complex coacervation microcapsules based on gelatin and gum Arabic.

A novel long-acting antifungal active film was successfully created, as an alternative to conventional chemical food preservatives. The antifungal films incorporated with cinnamaldehyde (CA) microcapsules achieved long-lasting antifungal activity, mitigated yellowing caused by the direct addition of CA, and showed improved flexibility properties. CA multinuclear microcapsules were produced using gelatin with a Bloom value of 200 and gum Arabic, resulting in increased encapsulation efficiency (99.

Improving the texture of braised pork by gradient-temperature heating and its molecular mechanism.

A novel gradient-temperature heating regime was proposed to improve the texture of braised pork. Compared with one-stage pressure heat treatment of around 107 °C, the gradient-temperature heat regime of preheating at 60 °C, followed by a slow increase of temperature to 107 °C and simmering at 97 °C increased the retention of immobilized water and reduced the shear force of meat. In this cooking regime, preheating treatment at 50-60 °C could promote the dissociation of thin and thick myofilaments, which contributed to a weakened shrinkage of myofibrils during the subsequent high temperature heating process.

Crucial textural properties of braised pork to evaluate the oral mastication behavior and its water distribution to influence tenderness.

The complex composition of braised pork, including lean meat, pigskin, and fat, makes it difficult for sensory evaluation of its texture properties. This study investigated the correlation between sensory texture attributes and physicochemical properties to achieve an objective and comprehensive evaluation of the texture of braised pork. Sensory analysis demonstrated that the overall texture acceptability of braised pork was significantly and negatively influenced by sensory texture attributes (including sensory hardness, chewiness, and toughness), while it was positively impacted by sensory adhesiveness, softness, and juiciness.

Disclosing the Nitrogen Sources via Isotope Labeling Technique and the Formation Mechanism of Pyrazine and Alkylpyrazines during the Heat Treatment of -(1-Deoxy-d-xylulos-1-yl)-alanine and Exogenous Alanine.

The formation pathway and mechanism of various pyrazines were investigated during the thermal treatment of the alanine-xylose Amadori compound (Ala-ARP) and exogenous alanine (Ala). -labeled Ala was used to coheated with Ala-ARP to clarify the nitrogen sources and the respective contributions of exogenous Ala and the regenerated Ala released from Ala-ARP to different pyrazine formation. It was found that exogenous Ala exhibited a priority in capturing glyoxal (GO) to form pyrazine during the thermal degradation of ARP.

Microwave-induced heterogeneity in protein conformation and water mobility interferes with the distribution pattern and migration pathway of sodium ion in myofibrillar protein gel.

The aim of this study was to investigate the distribution pattern and migration pathway of sodium ion in the myofibrillar protein (MP) gel matrix during microwave heating. The results showed that the content of sodium ions in the outer layer of MP gel increased by 47.85% compared with that in the inner layer.

Accelerated Degradation of DiXyl-α,ε-Lys-ARP via Interaction between Extra-Added Xylose and Monosubstituted Lys-ARPs during Maillard Reaction.

Lysine (Lys) is capable of forming a di-substituted Amadori rearrangement product (ARP) with xylose (Xyl), designated as diXyl-α,ε-Lys-ARP. DiXyl-α,ε-Lys-ARP degradation was characterized by two steps: Initially, Xyl-α- and Xyl-ε-Lys-ARP were formed through elimination or hydrolysis at specific α/ε positions of the corresponding enol and imine intermediates, which were then further degraded to dicarbonyl compounds and regenerated Lys. Xyl-α- or Xyl-ε-Lys-ARP had a reactive free amino group (ε-NH or α-NH), both of which were still highly reactive and able to undergo further reactions with Xyl.

Characteristic volatile compounds contributed to aroma of braised pork and their precursor sources.

The characteristic aroma compounds of traditional braised pork were investigated by gas chromatography-mass spectrometry-olfactometry (GC-MS-O), odor-activity values, and aroma recombination and omission experiments. A total of 56 volatile compounds were detected by GC-MS, among which hexanal, octanal, nonanal, (E)-2-octenal, 2,3-octanedione, 1-octen-3-ol, 2-pentylfuran, methanethiol, and dimethyl trisulfide were identified as the key aroma compounds by molecular sensory science. Partial least squares regression analysis indicated that some aroma compounds significantly contributed to fatty (hexanal, heptanal, 2-pentylfuran, nonanal, and (E)-2-octenal), meaty (methanethiol, dimethyl disulfide, dimethyl trisulfide, and octanal), sauce-like flavor (3-hydroxy-2-butanone and 2-furfural), and sweet, caramel (2,3-octanedione, 1-octen-3-ol).

Difference comparison of characteristic aroma compounds between braised pork cooked by traditional open-fire and induction cooker and the potential formation cause under electromagnetic cooking.

The characteristic aroma compounds of braised pork were identified through molecular sensory science and PLSR analysis, and the difference between two cooking methods, traditional open-fire (BPF) and induction cooker (BPC), was compared. Seventeen aroma compounds with odor activity values (OAVs) > 1 were identified in both samples. BPF revealed higher OAVs for most of the aroma compounds compared to BPC, and the higher aroma quality.

Formation of Volatile Pyrazinones in Amadori Rearrangement Products and Maillard Reaction Systems and the Major Formation Pathways.

Amadori rearrangement products (ARPs) are gaining more attention for their potential usage in the food flavor industry. Peptide-ARPs have been studied, but pyrazinones that were theoretically found in the Maillard reaction (MR) have not been reported to be formed from small peptide-ARPs. This study found four pyrazinones: 1-methyl-, 1,5-dimethyl-, 1,6-dimethyl-, and 1,5,6-trimethyl-2(1)-pyrazinones in both MR and ARP systems.

Mechanism of Dihydromyricetin-Induced Reduction of Furfural Derived from the Amadori Compound: Formation of Adducts between Dihydromyricetin and Furfural or Its Precursors.

Dihydromyricetin (DMY) was employed to reduce the yield of furfural derived from the Amadori rearrangement product of l-threonine and d-xylose (Thr-ARP) by trapping Thr-ARP, 3-deoxyxyosone (3-DX), and furfural to form adducts. The effect of different concentrations of DMY at different pH values and temperatures on the reduction of furfural production was studied, and the results showed that DMY could significantly reduce furfural production at higher pH (pH 5-7) and lower temperature (110 °C). Through the surface electrostatic potential analysis by Gaussian, a significant enhancement of the C nucleophilic ability at higher pH (pH ≥ 5) was observed on DMY with hydrogen-dissociated phenol hydroxyl.

Exogenous Alanine Promoting the Reaction between Amadori Compound and Deoxyxylosone and Inhibiting the Formation of 2-Furfural during Thermal Treatment.

The involvement of exogenous alanine was observed to inhibit the generation of 2-furfural during the thermal degradation of the Amadori rearrangement product (ARP). To clarify the reason for the reduced yield of 2-furfural triggered by exogenous alanine, the evolution of the precursors of 2-furfural formed in the ARP model and ARP-alanine model was investigated, and a model including ARP and -labeled alanine was used to differentiate the role of endogenous and exogenous alanine in the degradation of ARP. It was found that the condensation between ARP and 3-deoxyxylosone could occur during thermal treatment.

Rapid preparation of the Amadori rearrangement product of glutamic acid - xylose through intermittent microwave heating and its browning formation potential in microwave thermal processing.

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.

Machine Learning Accelerated Discovery of Functional MXenes with Giant Piezoelectric Coefficients.

Efficient and rapid screening of target materials in a vast material space remains a significant challenge in the field of materials science. In this study, first-principles calculations and machine learning algorithms are performed to search for high out-of-plane piezoelectric stress coefficient materials in the MXene functional database among the 1757 groups of noncentrosymmetric MXenes with nonzero band gaps, which meet the criteria for piezoelectric properties. For the monatomic MXene testing set, the random forest regression (RFR), gradient boosting regression (GBR), support vector regression (SVR), and multilayer perceptron regression (MLPR) exhibit values of 0.

Analysis of the browning reaction in a sorbitol/glycine model: Formation and degradation of precursors, glucose and α-dicarbonyl compounds during heating.

Browning can occur in the matrices of alditol and amino acids due to heating or long-term storage, which poses challenges in achieving the desired appearance stability. To investigate the mechanism of browning in the sorbitol-glycine system, we evaluated the evolution of typical intermediates, including glucose and α-dicarbonyl compounds (α-DCs), during heating at 100 ˚C. The browning index and intermediate products of the sorbitol-glycine system increased more rapidly compared to those of the sorbitol system.

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.

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.

Feasibility Study of Amadori Rearrangement Products of Glycine, Diglycine, Triglycine, and Glucose as Potential Food Additives for Production, Stability, and Flavor Formation.

Amadori rearrangement products (ARPs), as intermediates of the Maillard reaction (MR), are potential natural flavor additives but there is a lack of investigation especially in oligopeptide-ARPs. This study for the first time conducted a systematic analysis in comparing ARPs of glycine, diglycine, triglycine, and glucose to corresponding classic MR systems, including production, stability, and flavor analysis. The ARPs were effectively produced by prelyophilization with heating at 70 °C for 60 min and purified to 96% by a two-step purification method.

Efficient Formation of -(1-Deoxy--ribulos-1-yl)-Glutathione via Limited Oxidation and Degradation of Glutathione during the Atmospheric-Vacuum Thermal Reaction.

The efficient preparation of the ribose-glutathione (Rib-GSH) Amadori rearrangement product (RG-ARP) as a potent precursor of meaty flavor was studied through the atmospheric-vacuum thermal reaction. Liquid chromatography-mass spectrometry (LC-MS) analysis revealed that the oxidation and degradation of GSH occurred during the preparation of RG-ARP via the atmospheric thermal reaction, especially at a low molar ratio of Rib to GSH and high reaction temperature. The RG-ARP and the ARPs derived from the products of GSH oxidation and degradation with the participation of Rib were identified by MS/MS as -(1-deoxy-d-ribulos-1-yl)-glutathione, -(1-deoxy-d-ribulos-1-yl)-cysteinylglycine, and -(1-deoxy-d-ribulos-1-yl)-glutathione disulfide.

Regulated Formation of Inhibited Color and Enhanced Flavor Derived from Heated 2-Threityl-Thiazolidine-4-Carboxylic Acid with Additional Cysteine Targeting at Different Degradation Stages.

This study explored the addition of cysteine (Cys) affecting the color formation of heated 2-threityl-thiazolidine-4-carboxylic acid (TTCA) models under different reaction conditions and pointed out that temperature was considered to be the key parameter influencing the color inhibition behavior of Cys on TTCA reaction models. Results revealed that additional Cys not only controlled the reaction progress and blocked the formation pathway of browning but also changed the formation rate, intensity, and profile of the flavor generated from the TTCA reaction model. Meanwhile, the mechanism of Cys simultaneously regulating the formation of color and flavor was revealed through monitoring of the characteristic downstream products during TTCA degradation and model reaction systems.

Promotion or Inhibition Effects of Exogenous Glutathione-Degraded Amino Acids on the Formation of 2,3-Butanedione and Pyrazines via Varied Pathways of Interaction with α-Dicarbonyl Compounds Derived from -(1-Deoxy-d-xylulos-1-yl)-alanine.

The contribution of glutathione (GSH) and free amino acids degraded from GSH to the generation of pyrazines and 2,3-butanedione was illustrated during their interaction in the thermal treatment of the Amadori compound of alanine and xylose (ARP). GSH-degraded amino acids, glutamic acid (Glu), cysteine (Cys), and glycine (Gly), but not pyroglutamic acid (pGlu), could effectively capture α-dicarbonyls to facilitate the formation of pyrazines when ARP was heated with GSH. Deoxypentosones, the precursors of 2,3-butanedione, were largely consumed in the ARP-GSH model by the interaction with GSH and its degradative Cys compared with the ARP model.

Changes of lipid oxidation, volatile and taste-active compounds during pan-heating of pork belly.

This study investigated the mechanisms underlying the evolution and formation of aroma and taste-active compounds of pork belly in representative traditional pork cuisines during pan-heating. The results revealed that as the temperature increased to 110 ℃, the unsaturation of fatty acids decreased from 60.25 % to 58.

Exogenous Threonine-Induced Conversion of Threonine-Xylose Amadori Compound to Heyns Compound for Efficiently Promoting the Formation of Pyrazines.

The involvement of exogenous threonine during the degradation of l-threonine-d-xylose Amadori rearrangement product (Thr-ARP) was found to promote the formation of pyrazines. A model including Thr-ARP and N-labeled l-threonine was applied to reveal the role of free threonine in Thr-ARP conversion to pyrazines. Quantitative analyses of pyrazines in the model of Thr-ARP/N-labeled threonine showed a precedence of the endogenous threonine (formed by the degradation of Thr-ARP) over the exogenous threonine in pyrazines formation, and the ratio of N to N content in pyrazines increased significantly over time.

Evolution of lean meat tenderness stimulated by coordinated variation of water status, protein structure and tissue histology during cooking of braised pork.

Tenderness of lean meat in braised pork is of great importance to the consumer palatability and acceptance. The influence of water status, protein structure and histological changes on lean meat tenderness during cooking was investigated. Results indicated that lean meat began to tenderize mainly after 20 min-cooking.