Effect of sodium chloride concentration on off-flavor removal correlated to glucosinolate degradation and red radish anthocyanin stability.

Anthocyanin-rich concentrates from different red radish can be used as natural food colorants. However, the development of off-flavor during extraction has been major challenge in processing industries. This work aimed to evaluate the effect of sodium chloride (NaCl) concentration in phosphoric acidified medium pH 2.5 on removal of off-flavor from red radish anthocyanin. The effect of NaCl concentration on anthocyanin properties was also evaluated. Results showed that the total glucosinolate was highly degraded at high NaCl concentration (< 500 mM) compared with control, leading to higher off-flavor development. Additionally, the glucosinolate degradation was positively and significantly correlated to isothiocyanate, while was negatively and significantly correlated with dimethyl di-, trisulfide, cedrol, triacetin, 6-methyl-5-hepten-2-one. Moreover, total monomeric and color properties of extracted anthocyanins were degraded at high NaCl concentration (< 500 mM) compared with control. The tentative anthocyanin identification by UPLC-TQ-MS showed 12 glycosylated anthocyanins substituted at C3 and C5 in tested anthocyanin extracts. In conclusion, higher NaCl concentration (< 500 mM) could not be useful for red radish off-flavor removal and anthocyanin properties.

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.

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.

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. Shear force and texture profile analysis (TPA) variables, reflecting mastication behavior, were used to characterize the textural properties of braised pork. They were closely related to water distribution, with a higher proportion of immobilized water (P21), indicating a higher water holding capacity and a more tender texture. Correlation analysis between sensory texture attributes and physicochemical properties through partial least squares regression further revealed significant associations between shear force, TPA variables, and sensory texture attributes. Moreover, the proportion of immobilized water (P21) significantly and negatively affected sensory hardness and chewiness, whereas the proportion of free water (P22) significantly influenced sensory toughness. Sensory texture attributes could be well predicted by the physicochemical properties by projecting test samples onto calibration models established by known samples. Therefore, a combination of sensory and instrumental measures can reliably reflect the texture properties of braised pork. PRACTICAL APPLICATION: The combination of sensory and instrumental methods is an effective strategy to accurately and objectively evaluate the texture properties of braised pork, which overcomes the limitations caused by the complexity of the composition and texture traits of braised pork. The accurate evaluation and standardization of texture properties is an important premise for the repeatable and stable cooking of traditional braised pork. Furthermore, this research method and findings can also be applied to guide the procedural optimization of smart appliances (e.g., induction cookers) for cooking braised pork.

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.

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.

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.

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.

Effects of tannic acid interfacial absorption on the physicochemical stability of algal oil-loaded emulsions and inhibition of fishy off-flavor.

In the present study, the inhibition of fishy off-flavor and destabilization in algae oil-loaded emulsions by tannic acid (TA) adsorption on octenyl succinic anhydride (OSA) starch interfaces were investigated. The changes of typical fishy off-flavor components in the emulsion, physiochemical stability, and interaction between TA and OSA starch were analyzed. The TA fortification significantly prevented the production of fishy smell-related volatile components such as heptanal and (E, E)-3, 5-octadiene-2-one. The proportion of TA on the interface was more than 90 %, forming an interfacial film with the antioxidant function. The emulsions stabilized by OSA starch-TA complexes had better oxidative and physical stability. The isothermal titration calorimetry suggested that the interaction between OSA starch and TA included hydrogen bonding and van der Waals forces (ΔG = -13.272 kJ·mol-1·K-1, ΔH = -1.302 × 103 kJ·mol-1, ΔS = -4.326 kJ·mol-1·K-1). Altogether, these results provided application guidance for developing starch-based oil-in-water emulsion systems with antioxidant properties.

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.

Effect of tannic acid-OSA starch complexation on the binding capacity and release of aldehydes off-flavor in aqueous matrix.

In order to further clarify the regulation of tannic acid on the off-flavor in starch-based algal oil emulsions, the effect of different starch matrix (OSA starch and OSA starch-tannic acid complex) on the release capacities of aldehydes (pentanal, hexanal, heptanal, nonanal) were investigated. The adsorption and retention ability, thermodynamic parameters, and hydrophobicity of aldehydes in the starch matrix were analyzed. Nonanal exhibited the strongest adsorption ability (65.01%-85.69%) with the starch matrix, followed by heptanal, hexanal, and pentanal, which accounted for the structures of aldehydes. Furthermore, aldehydes had a higher affinity with complex (16.33%-83.67%) than OSA starch (9.70%-66.71%) because the tannic acid altered the structure of OSA starch. Isothermal titration calorimetry suggested that the interaction between the starch matrix and aldehydes was an entropy-driven spontaneous endothermic reaction, and hydrophobic interactions were the predominant driving forces. Altogether, these results lay a theoretical foundation for facilitating the regulation of flavor in starch foods.

Hydrophobic-action-driven removal of six organophosphorus pesticides from tea infusion by modified carbonized bacterial cellulose.

The abuse of organophosphorus pesticides (OPPs) in tea planting makes it easy to transfer from tea into its infusion, bringing potential health risks to consumers. Thus, it is essential to adopt reliable techniques to remove OPPs from tea infusion. In this study, three treatment methods were used to modify carbonized bacterial cellulose (CBC) to improve its adsorption performance. Among them, CBC treated by hydrazine hydrate (N-CBC) had the best adsorption effect, whose removal rate for dicrotophos is 13 times that of CBC. The in-depth study of adsorption mechanism proved that hydrophobic interaction dominated the adsorption of OPPs onto N-CBC. The pseudo-second-order kinetic model and Langmuir isotherm model were more suitable to describe the process. Additionally, there were no significant changes in tea infusion quality after N-CBC treatment. This work clarifies that N-CBC benefitted from simple preparation method, excellent adsorption performance and unique adsorption mechanism has potential applications in tea infusion.

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 58.71 %, while the content of free radicals and secondary oxidation products increased. At the later heating stages, the addition of spices and increased heating temperature (150 â„ƒ) led to continuous increments in the contents (from 958.20 µg/kg to 1511.88 µg/kg) and diversity of volatile compounds in pork belly, imparting the unique aroma. Additionally, the accumulation of low-molecular-weight peptides, free amino acids, and nucleotides not only provided the substrate for thermal reactions and their synergistic effects, but also contributed to the desired taste quality. These findings offered insights into the flavor formation mechanisms of traditional pork cuisines and provided direction for further research.

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

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.

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

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.

Quickly and efficiently remove multiple pesticides in tea infusions by low-cost carbonized bacterial cellulose.

Soaking tea leaves make tea consumers exposure to pesticide residues more easily. However, there are few studies on the removal of pesticides in tea infusions. Therefore, a low-cost carbonized bacterial cellulose material was prepared by direct calcination method, and used to remove multiple pesticides in tea infusions quickly and efficiently. CBC-350 has the best removal efficiency for 9 pesticides and then screened the best adsorption conditions. The adsorption isotherm experiment was carried out and indicated that the adsorption process was in consist with the Freundlich model. The thermodynamic parameters are also calculated. Moreover, the adsorption mechanism was discussed, which suggests that π-π interaction and hydrophobic action are the driving force during the adsorption process. Exhilaratingly, the CBC-350 also has excellent adsorption capacity compared to other adsorbents and can be reused at least five times.

Formation Priority of Pyrazines and 2-Acetylthiazole Dependent on the Added Cysteine and Fragments of Deoxyosones during the Thermal Process of the Glycine-Ribose Amadori Compound.

In this study, it was found that extra-added cysteine (Cys) became involved in volatile compound formation during the Maillard reaction of the glycine-ribose Amadori rearrangement product (GR-ARP). The priority of the Cys reaction with different α-dicarbonyls and its dependence on the Cys dosage were investigated. At the same concentrations of methylglyoxal (MGO) and glyoxal (GO), it was found that 2-acetylthiazole was the dominant product when the molar ratio of Cys to MGO was 1:1, while formation of pyrazines was improved when the Cys percentage increased. Cys preferentially reacted with MGO first rather than GO to exclusively generate 2-acetylthiazole at a high yield. The concentration of 2-acetylthiazole quickly increased up to a plateau and remained stable during further heat treatment. When MGO was totally consumed, remaining Cys began to react with GO through the predominant pathway where the keto form of carbonylcysteimine derived from Cys and GO was hydrolyzed to recover GO with cysteamine formation, whereas the hydrolysis reactivity of enolized carbonylcysteimine as the Strecker pathway for generation of pyrazines was relatively low. During the heat treatment of GR-ARP, the constantly lower ratios of α-dicarbonyls to Cys led to inhibited formation of 2-aminopropanal, which accounted for the decreased methylpyrazine yields.

Microwave heating and conduction heating pork belly: Non-volatile compounds and their correlation with taste characteristics, heat transfer modes, and matrix microstructure.

This study investigated the difference in the taste characteristics of pork belly cooked by traditional pan-heating (TH), microwave heating (MH), and microwave combined with conduction heating (MH + CH). The results showed that MH destroyed the microstructure integrity and made the cooking loss (50.33%) and sodium ion concentration (10.8 mg/g) about 1.6 times that of MH + CH, thereby enhancing the saltiness. In addition, compared with TH, microwave heating could accelerate the hydrolysis of proteins and the thermal degradation of ribonucleotides, resulting in higher contents of free amino acids (880.71 and 714.85 mg/100 g) and nucleotides (181.41 and 145.52 mg/100 g) in MH and MH + CH. Combined with the results of non-volatile compounds and sensory evaluation, the MH + CH not only promoted the accumulation but also improved the dissolution uniformity of taste compounds, which enhanced the sensory umami. The inconsistency between non-volatile compounds, electronic tongue, and sensory evaluation indicated that the matrix effects caused by cooking also had significant influences on the taste quality of solid samples.

Flavor and texture characteristics of microwave-cooked Kung Pao Chicken by different heat conduction effects and further aroma improvement with moderate enzymatic hydrolyzed chicken fat.

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.

Proline-glucose Amadori compounds: Aqueous preparation, characterization and saltiness enhancement.

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 (C11H19O7N, 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.