Novel electronic structures and enhanced optical properties of boron phosphide/blue phosphorene and F4TCNQ/blue phosphorene heterostructures: a DFT + NEGF study.

Blue phosphorene (Blue-p), an allotrope of black phosphorene, has attracted extensive interest due to its hexagonal crystal with a flat arranged layer of phosphorus atoms. However, the indirect band gap of Blue-p greatly hinders its applications in optoelectronics. By stacking both boron phosphide (BP) and the organic molecule 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) with Blue-p, we construct BP/Blue-p and F4TCNQ/Blue-p heterostructures. We reveal that the BP/Blue-p heterostructure possesses a direct band gap of 0.605 eV and is tunable via in-plane strain and an external electric field. Moreover, it also has remarkable optical absorption in the UV region and enhanced transport properties. Furthermore, by doping with F4TCNQ, the F4TCNQ/Blue-p heterojunction displays type-II semiconducting properties with a flat valence band and Van Hove singularities at the Fermi level, which can be used to achieve extremely low in-band tunneling, yielding low static power dissipation and large drive currents in the ON regime of transistors. Due to the superior electronic, optical and transport properties, Blue-p-based heterostructures are promising candidates for electronic and optical device applications.

Effect of Temperature on Flavor Compounds and Sensory Characteristics of Maillard Reaction Products Derived from Mushroom Hydrolysate.

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.

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 R2 values of 0.80, 0.80, 0.89, and 0.87, respectively. Expanding our analysis to the entire MXene data set, the best active learning cycle finds more than 140 and 22 MXenes with out-of-plane piezoelectric stress coefficients (e31) exceeding 3 × 10-10 and 5 × 10-10 C/m, respectively. Moreover, thermodynamic stabilities were confirmed in 22 MXenes with giant piezoelectric stress coefficients and 9 MXenes with both large in-plane (d11 > 15 pm/V) and out-of-plane (d31 > 2 pm/V) piezoelectric strain coefficients. These findings highlight the remarkable capabilities of machine learning and its optimization algorithms in accelerating the discovery of novel piezoelectric materials, and MXene materials emerge as highly promising candidates for piezoelectric materials.

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. After heating for 10 h, the browning index of the sorbitol-glycine system was eight times higher than that of sorbitol alone. In the presence of glycine, sorbitol underwent continuous conversion into glucose. After 10 h of heating, the concentration of glucose in the sorbitol-glycine system reanched 726.6 mg/L, which was approximately 63 times higher than that in the sorbitol system. Mass spectrometry analysis revealed the presence of α-DCs such as 3-deoxyglucosone (3-DG), glyoxal (GO), methylglyoxal (MGO), 2,3-butanedione (2,3-BD), in the sorbitol-glycine system. These compounds were precursors of melanoidins, indicating the occurrence of the Maillard reaction and resulting in the browning of the system. Therefore, the browning process in the sorbitol-glycine system involved two stages of reactions: the conversion of sorbitol to glucose and the Maillard reaction between glucose and glycine.

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. In the inner layer of protein gel, the non-covalent disulfide bonds (mainly ε(γ-Glu)-Lys) increased (P < 0.05), which contributed to the formation of a better rigid structure of the protein. The free water content was significantly higher than that of the inner layer (P < 0.05), which was related to the higher mobility of sodium ions. The results of microstructure analysis showed that the outer layer of the MP gel formed a more porous network than the inner layer. This work is expected to give some insights into the development of promising salt-reduced meat products by microwave heating.

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. Aroma recombination and omission experiments confirmed that twelve aroma compounds significantly contributed to the characteristic aroma of braised pork, and eight compounds such as hexanal, (E)-2-octenal, and methanethiol were further confirmed as important contributors by PLSR analysis. Furthermore, PLSR analysis clarified the role of aldehydes such as hexanal, (E)-2-octenal, and (E,E)-2,4-decadienal in contributing to fatty attribute, whereas methanethiol was responsible for the meaty aroma. These characteristic aroma compounds mainly derived from lean meat due to its high content of phospholipids, and the exogenous seasonings contributed to the balanced characteristic aroma profile of braised pork by altering the distribution of these characteristic aroma compounds. Variations in heating parameters affected the formation of lipid oxidation and Strecker degradation products, which might explain aroma discrepancy between braised pork cooked by two methods with different heat transfer efficiencies.

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 Nα/Nε 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-NH2 or α-NH2), both of which were still highly reactive and able to undergo further reactions with Xyl. Therefore, the diXyl-α,ε-Lys-ARP/Xyl model system was established to explore the impact of extra-added Xyl on diXyl-α,ε-Lys-ARP degradation behavior. Extra-added Xyl remarkably affected the degradation pathway of diXyl-α,ε-Lys-ARP by capturing the Xyl-α- and Xyl-ε-Lys-ARP to regenerate diXyl-α,ε-Lys-ARP. This interaction between Xyl and mono-substituted Lys-ARPs promoted the shift of chemical equilibrium toward the degradation of diXyl-α,ε-Lys-ARP, thereby accelerating its degradation rate. This degradation was markedly facilitated by the elevated temperature and pH values. Interestingly, the yield of Xyl-α- and Xyl-ε-Lys-ARP was particularly dependent on the pH during diXyl-α,ε-Lys-ARP degradation. Xyl-ε-Lys-ARP was the dominant product at pH 5.5-7.5 while Xyl-α-Lys-ARP possessed a relatively higher content under weak alkaline conditions, which was related to the reactivities of the Nα/Nε positions under various reaction conditions.

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 C6 nucleophilic ability at higher pH (pH ≥ 5) was observed on DMY with hydrogen-dissociated phenol hydroxyl. The nucleophilic ability of DMY led to its trapping of Thr-ARP, 3-DX, and furfural with the generation of the adducts DMY-Thr-ARP, DMY-3-DX, and DMY-furfural. The formation of the DMY-Thr-ARP adduct slowed the degradation of Thr-ARP, caused the decrease of the 3-DX yield, and thereby inhibited the conversion of 3-DX to furfural. Therefore, DMY-Thr-ARP was purified, and the structure was identified by nuclear magnetic resonance (NMR). The results confirmed that C6 or C8 of DMY and carbonyl carbon in Thr-ARP underwent a nucleophilic addition reaction to form the DMY-Thr-ARP adduct. In combination with the analysis results of Gaussian, most of the DMY-Thr-ARP adducts were calculated to be C6-DMY-Thr-ARP. Furthermore, the formation of DMY-furfural caused furfural consumption. The formation of the adducts also shunted the pathway of both Thr-ARP and 3-DX conversion to furfural, resulting in a decrease in the level of furfural production.

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. 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.

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 15N-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. Nevertheless, the interaction of ARP with 3-deoxyxylosone exhibited an accelerated pace in the presence of exogenous alanine. In this way, exogenous alanine blocked the recovery of endogenous alanine while simultaneously enhancing the consumption of ARP and 3-deoxyxylosone during the Maillard reaction. Hence, the yield of 2-furfural was diminished with the interference of exogenous alanine. Furthermore, the promotion of the reaction between ARP and deoxyxylosone induced by exogenous alanine blocked their retro-aldolization reaction to short-chain α-dicarbonyls (α-DCs) and consequently resulted in a lack of pyrazine formation during the ARP degradation. The present study provided a feasible method for the controlled formation of 2-furfural during the thermal treatment of ARP derived from alanine.

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). Lean meat produced more aldehydes, alcohols, ketones, and sulfur-containing compounds than subcutaneous fat. The seasonings (saccharose, cooking wine, and soy sauce) facilitated the formation of ethyl L-lactate, 2-acetylfuran, 2-furfural, 5-methyl-2-furaldehyde, 2-methyl-pyrazine, and 2-acetylpyrrole. Meanwhile they reduced the content of lipid oxidation products, thereby stimulated the characteristic aroma of the Chinese traditional braised pork.

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. Correlated with the stability order of amino compounds (glycine > diglycine > triglycine), the stability order of ARPs was Gly-ARP > Digly-ARP ≈ Trigly-ARP. In a negative correlation with heating temperature and time, ARPs were less stable than original amino compounds at high temperatures (100, 130, and 160 °C). ARPs exhibited better flavor formation ability in pyrazines and furans than MR systems, with similar flavor compositions but different preferences. Diglycine- and triglycine-ARPs exhibited better flavor formation efficiency than glycine-ARP. Heating temperature and time, initial pH, and carbon chain length were found to be the parameters that affect the stability and flavor formation of ARPs. This study suggested that ARPs, especially peptide-ARPs, have great potential for usage as food flavor additives in the future.

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(1H)-pyrazinones in both MR and ARP systems. It was the first time 1-methyl-2(1H)-pyrazinone was reported, along with 1,5-dimethyl- and 1,5,6-trimethyl-2(1H)-pyrazinones being purified and analyzed by nuclear magnetic resonance for the first time. The primary formation routes of the pyrazinones were also proven as the reaction between diglycine and α-dicarbonyls, including glyoxal, methylglyoxal, and diacetyl. The pyrazinones, especially 1,5-dimethyl-2(1H)-pyrazinone, have strong fluorescence intensity, which may be the reason for the increase of fluorescence intensity in MR besides α-dicarbonyls. Cytotoxicity analysis showed that both Gly-/Digly-/Trigly-ARP and the three pyrazinones [1-methyl-, 1,5-dimethyl-, and 1,5,6-trimethyl-2(1H)-pyrazinones] showed no prominent cytotoxicity in the HepG2 cell line below 100 µg/mL, further suggesting that ARPs or pyrazinones could be used as flavor additives in the future. Further research should be conducted to investigate pyrazinones in various systems, especially the peptide-ARPs, which are ubiquitous in real food systems.

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. 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.

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 15N-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/15N-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 15N to 14N content in pyrazines increased significantly over time. According to the observed occurrence of the Heyns rearrangement products (HRP) derived from 15N-threonine, as well as the sharp decrease of 15N-threonine content and a rapid increase of 14N endogenous threonine at the initial stage of heat treatment, it was proposed that aldimine condensation between exogenous threonine and Thr-ARP followed by the hydrolysis led to the endogenous threonine and the generation of HRP. Then, the HRP underwent dehydration followed by hydrolysis to form exogenous threonine and deoxyxyosones, and the dehydration and hydrolysis of deoxyxyosones to form organic acids was inhibited, but the retro-aldolization of deoxyxyosones was promoted, facilitating the generation of reactive α-dicarbonyl compounds. In this way, exogenous threonine accelerated the release of endogenous threonine and α-dicarbonyl compounds and the pH decline was slowed down, which was favorable for the formation of pyrazines.

Reduced asynchronism between regenerative cysteine and fragments of deoxyosones promoting formation of sulfur-containing compounds through extra-added xylose and elevated temperature during thermal processing of 2­threityl-thiazolidine-4-carboxylic acid.

The flavor intensity of thermally processed 2­threityl-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 selective encapsulation and stabilization of cinnamaldehyde and eugenol in high internal phase Pickering emulsions: Regulating the interfacial properties.

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.

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. In the early period of cooking, the decrease of total sulfhydryl content caused the protein oxidative cross-linking, leading to the gradual unfolding of the protein structure, thus resulting in a decrease of T22 and an increase of centrifugal loss, which decreased the tenderness of lean meat. However, after cooking for 20 min, the ß-sheet decreased and random coil increased, thus generating conversion between P21 and P22. The rupture of perimysium structure was observed. Changes in protein structure, water status, and tissue histology could facilitate the initiation and development of lean meat tenderness.

Controlled Selective Formation of Amadori Compounds from α/ε Mono- or Di-glycation of Lysine with Xylose.

Three Amadori rearrangement products (Xyl-α-Lys-ARP, Xyl-ε-Lys-ARP, and diXyl-α,ε-Lys-ARP) were observed in the xylose-lysine (Xyl-Lys) Maillard reaction model. They were separated and characterized by liquid chromatography with tandem mass spectrometry and NMR. The crucial roles of reaction temperature, pH, molar ratio of Xyl to Lys, and reaction time in the formation of different Xyl-Lys-ARPs were investigated. The proportion of Xyl-α-Lys-ARP among all Xyl-Lys-ARPs was increased to 48.41% (its concentration was 25.31 µmol/mL) after the reaction at pH = 5.5 and a molar ratio of 3:1 (Xyl: Lys) for 9 min, while only Xyl-ε-Lys-ARP was generated at a higher pH (7.5) and a lower molar ratio of 1:5. Moreover, the much higher activation energy (84.08 kJ/mol) of diXyl-α,ε-Lys-ARP than Xyl-α-Lys-ARP (34.19 kJ/mol) and Xyl-ε-Lys-ARP (32.32 kJ/mol) indicated a pronounced promoting effect on diXyl-α,ε-Lys-ARP formation by high temperatures. A complete conversion from Xyl-α-Lys-ARP and Xyl-ε-Lys-ARP to diXyl-α,ε-Lys-ARP was achieved through the reaction time prolongation and Xyl concentration increase at a higher temperature; the concentration of diXyl-α,ε-Lys-ARP was 39.05 µmol/mL at a molar ratio of 5:1 for 40 min. Accordingly, the selective preparation of Xyl-α-Lys-ARP, Xyl-ε-Lys-ARP, and diXyl-α,ε-Lys-ARP could be achieved through adjusting the Xyl-Lys ratio, pH, and reaction time.

Improved tenderness and water retention of pork pieces and its underlying molecular mechanism through the combination of low-temperature preheating and traditional cooking.

The effects of two-stage heating with different preheating combinations on the shear force and water status of pork-pieces were explored. The results showed that the combined preheating at 50 ℃ for 35 min or at 60 ℃ for 5 or 20 min with traditional high temperature heating reduced the shear force and improved the water retention of meat, which was attributed to uniformly separation of myofibers and smaller myofiber space. Visible dissociation of actomyosin in heating groups of 50 ℃-35 min, and 60 ℃-5, 20 min was related to the tenderization of meat. The higher surface hydrophobicity, tryptophan fluorescence intensity, and lower α-helices of actomyosin at 60 ℃ contributed to the liberation of actin. However, severe oxidation of sulfhydryl groups at 70 ℃ and 80 ℃ promoted the aggregation of actomyosin. This study presents the advantage of two-stage heating in improving meat tenderness and juiciness and its underlying mechanisms.