Conformational changes induced by selected flavor compounds from spices regulate the binding ability of myofibrillar proteins to aldehyde compounds.

Interactions among flavor compounds from spices (FCS) and myofibrillar proteins (MP) were investigated. Fluorescence and Fourier transform infrared spectroscopy showed that hydrogen bonding and hydrophobic interactions were the main binding forces between FCS and MP. The FCS increased the particle size and SH content of MP and caused a reduction of zeta potential from -5.23 to -6.50 mV. Furthermore, FCS could modify the binding ability of MP and aldehydes. Eugenol reduced the ability of MP to bond with aldehydes by 22.70-47.87 %. Molecular dynamics simulations demonstrated that eugenol may combat nonanal to attain binding site of amino acid residue (PHE165) and induce protein conformational changes. Electrostatic interactions and van der Waals forces within myosin-nonanal may be disrupted by these alterations, which could reduce stability of complex and cause release of nonanal. This study could provide new insights into regulating the ability of proteins to release and hold flavors.

Insights into flavor formation of braised chicken: Based on E-nose, GC-MS, GC-IMS, and UPLC-Q-Exactive-MS/MS.

Effects of braising duration on volatile organic compounds (VOCs) and lipids in chicken were investigated. Aroma profiles identified by an electronic nose were effective in differentiating braising stages. During braising process, a total of 25 key VOCs were detected in braised chicken, and sample braised for 210 min exhibited the highest level of key VOCs. Additionally, a gas chromatography mass spectrometry fingerprint was established to evaluate the distribution of VOCs throughout the braising process. Partial least square discriminant analysis indicated that 2-heptanone, 3-methyl-2-butanone, octanal, nonanal, butanal, (E)-2-pentenal, 1-octen-3-ol, 1-hexanol, pentanal, hexanal, and 1-pentanol significantly affected flavor characteristics of braised chicken. Furthermore, 88 differential lipids were screened, and glycerolipids metabolic was found to be main metabolic pathway during braising process. Triglycerides (TG) and phosphatidyl ethanolamine (PE), such as TG (16:0/18:1/18:2), TG (18:0/18:1/18:2), TG (18:1/18:2/18:3), TG (18:1/18:1/18:2), PE (O-18:2/18:2), PE(O-18:2/18:1), and TG (16:0/16:1/18:2), played a vital role in the generation of VOCs.

Insights into the interactions between etheric compounds and myofibrillar proteins using multi-spectroscopy, molecular docking, and molecular dynamics simulation.

This study aimed to examine how the addition of etheric compounds (EC) affects the characteristics of myofibrillar proteins (MP) and to understand underlying interaction mechanisms. Fourier transform infrared spectroscopy confirmed that the EC-MP complex was formed through hydrogen bonding. The addition of EC resulted in an increase in the α-helix content and a decrease in the ß-sheet content of MP, which would promote the protein unfolding. The unfolding of MP led to aggregation and formation of larger and non-uniform particles. As a result, the exposure of negative charge on the MP surface was enhanced, and zeta potential was decreased from -5.33 mV to -7.45 mV. Moreover, the EC-induced modification of MP conformation resulted in a less rigid three-dimensional network structure of MP gel and enhanced the discharge of aldehyde compounds (C > 6). Moreover, the rheological characteristics of MP were enhanced by the suppression of protein-protein interactions due to the MP unfolding. Molecular dynamics simulations revealed that anethole reduced the binding capacity of myosin to decanal by raising its binding energy from -22.22 kcal/mol to -19.38 kcal/mol. In the meantime, anethole competed for the amino acid residue (PHE165) where myosin connects to decanal. This caused the hydrogen bonds and hydrophobic contacts between the two molecules to dissolve, altering myosin's conformation and releasing decanal. The results might be useful in predicting and controlling the ability of proteins to release and hold onto flavors.

Characterization of aroma profiles of chinese four most famous traditional red-cooked chickens using GC-MS, GC-IMS, and E-nose.

The aroma profile of the four most popular types of red-cooked chickens in China was analyzed using a combination of gas chromatography-mass spectrometry (GC-MS), gas chromatography-ion mobility spectrometry (GC-IMS), and electronic nose (E-nose). Principal component analysis (PCA) demonstrated that the E-nose could successfully distinguish between the four types of red-cooked chickens. Additionally, a fingerprint was created using GC-IMS to examine the variations in volatile organic compounds (VOCs) distribution in the four chicken types. A total number of 84 and 62 VOCs were identified in the four types of red-cooked chickens using GC-MS and GC-IMS, respectively. Odor activity value (OAV) showed that 1-octen-3-ol, heptanal, hexanal, nonanal, octanal, eugenol, dimethyl trisulfide, anethole, anisaldehyde, estragole, and eucalyptol were the key volatile components in all samples. Furthermore, partial least squares-discriminant analysis (PLS-DA) demonstrated that (E, E)-2,4-decadienal, dimethyl trisulfide, octanal, eugenol, hexanal, (E)-2-nonenal, 1-octen-3-ol, butanal, ethyl acetate, ethyl acetate (D), nonanal, and heptanal could be used as markers to distinguish aroma of the four types of red-cooked chickens. Also, it is worth noting that levels of VOCs varied between chicken breast muscle and skin. The obtained results offer theoretical and technological support for flavor identification and control in red-cooked chickens to enhance their quality and encourage consumer consumption, which will be advantageous for the red-cooked chicken production chain.

Exploring the interaction between myofibrillar proteins and pyrazine compounds: Based on molecular docking, molecular dynamics simulation, and multi-spectroscopy techniques.

Flavor is one of the most important factors that affect consumers' preference for processed meat products. This study aimed to investigate effects of heating on interaction between myofibrillar proteins (MPs) and pyrazine compounds and understand the underlying mechanisms. A combination of multispectral, molecular docking, and molecular dynamics technologies was used to achieve study's aim. Results demonstrated that MPs underwent structural reconstruction and expansion during heating, which significantly altered surface hydrophobicity and SH content. MPs' zeta potential reduced from -7.29 to -10.47 when a short heating time. Additionally, a positive correlation was found between ß-sheet content and ability of MPs to adsorb pyrazine compounds. Molecular docking analysis revealed 13 binding sites for pyrazines and MPs. Furthermore, amino acid residues and pyrazine compounds were found to interact by four different forms of forces, primarily van der Waals forces, carbon­hydrogen bonds, alkyl groups, and π-alkyl groups. Obtained results demonstrated that adequate or optimized heat treatment could expose more binding sites, hence enhancing the binding of MPs to pyrazine compounds. This study may be used to better understand how structural changes in MPs during processing affect MPs' capacity to bind flavor substances, which can help improve flavor of processed meats to encourage their consumption.

Structural changes induced by ultrasound improve the ability of the myofibrillar protein to bind flavor compounds from spices.

Effects of ultrasound (UT) treatments on the structural, physicochemical, and functional properties of myofibrillar proteins (MPs), as well as their ability to bind to flavor compounds from spices, were investigated. The results demonstrated that UT treatment enhanced surface hydrophobicity, SH content, and absolute ζ-potential value of the MPs. Atomic force microscopy analysis displayed formation of MPs aggregates with small particle size in the UT-treated MPs samples. Meanwhile, UT treatment could improve the emulsifying properties and physical stability of MPs' emulsion. Additionally, the MPs gel network structure and stability significantly improved following UT treatment. Changes in the structural, physicochemical, and functional properties enhanced the ability of MPs to bind to flavor substances from spices depending on the duration of UT treatment. Furthermore, correlation analysis showed that the ability of myristicin, anethole, and estragole to bind to MPs was highly correlated with surface hydrophobicity, ζ-potential value, and α-helix content of MPs. The results of this study may help in understanding the relationship between the changes in MPs properties during the processing of meat products and their ability to bind to flavors from spices, thereby improving flavors retention and taste of processed meat products.

Understanding interactions among flavor compounds from spices and myofibrillar proteins by multi-spectroscopy and molecular docking simulation.

Influence of the constant heating treatment on structural and adsorption properties of myofibrillar proteins (MPs) of chicken was investigated. The results showed that heat treatment enhanced the exposure of sulfhydryl groups and improved hydrophobicity of MPs surface. Particle size distribution of MPs significantly varied depending on heat treatment duration. Also, heat treatments resulted in significant changes in the α-helix and ß-sheet structures of MPs. Besides, the MPs formed larger, irregular, and cluster-like aggregates after heat treatments. Moreover, heat treatments increased viscosity and surface roughness of MPs, while zeta potential value was reduced after heat treatments. Furhthermore, binding interactions between the MPs and spices flavors signifcanlty varied relying on nature of MPs and flavor compounds, as well as heat treatments duration. Amino acid residues were interacted with flavor compounds of spices via a variety of bonds and a stable MPs-flavors complex was performed. The obtained results provide a basis for understanding structural and physicochemical changes that occur in MPs during cooking and the interactions between MPs and flavors of spices.

Effect of extrusion parameters on the interaction between rice starch and glutelin in the preparation of reconstituted rice.

Reconstituted rice produced by extrusion has been attracted attention due to nutritional fortification and convenient production. Nevertheless, how to achieve desirable qualities and physicochemical properties of reconstituted rice nearly to natural rice by regulating extrusion process parameters is difficult. Herein, rice starch/glutelin mixture as raw material of reconstituted rice was extruded at varying extrusion conditions. Specific mechanical energy (SME) and sectional expansion index (SEI) dropped with rise in density (R2 = 0.9117 and 0.8207). Solubility was enhanced with increase in product temperature (R2 = 0.9085), color darkened and shifted to reddish and yellowish as extrusion temperature increased (R2 = 0.8577). These trends were well fitted by sigmoid models. Furthermore, SME enhanced hydrophobic and electrostatic interactions between rice starch and glutelin and caused the reduction in crystallinity and thermal stability, promoting the formation of a bi-continuous matrix of protein aggregates with rice starch. The obtained results can be applied to guide the production of reconstituted rice with desirable qualities.

Fabrication of biodegradable blend plastic from konjac glucomannan/zein/ PVA and understanding its multi-scale structure and physicochemical properties.

Exploration and synthesis of degradable plastics can alleviate and avoid environmental pollution induced by petroleum-based plastics. In this study, a konjac glucomannan (KGM)/zein/PVA ternary blend plastic was successfully prepared by casting. The results showed that, despite the presence of particle aggregation from incompatible components in blend plastic, the addition of KGM and zein improved its compatibility which is consistent with the formation of continuous dark regions and the reduction of roughness average (Ra) results in the AFM characterization. Also, XRD and FT-IR results indicated that the addition of KGM and zein disrupted the molecular and crystalline structure of PVA, induced stretching vibration of alcohol and hydroxyl groups, and crystallinity reduction. In addition, KGM deacetylation (d-KGM) reduced the intramolecular hydroxyl groups, reduced the water absorption and water vapor transmission rate of the blend plastics, and increased the crystallization temperature (Tc) and melting temperature (Tm). Furthermore, the blended plastics exhibited the best tensile strength (TS), elongation at break (E), and elastic modulus (EM) when the proportion of KGM to zein was 9:1. Notably, the blended plastic with KGM and zein added displayed more pores and cracks after soil burial, implying that the lack of degradability of pure PVA plastic was improved.

Effects of various microwave intensities collaborated with different cold plasma duration time on structural, physicochemical, and digestive properties of lotus root starch.

Lotus root starch was treated with single and combined microwave (300 and 700 W) and cold plasma (60, 90, and 120 s) treatments. Effects of treatments on multi-structural, physicochemical, and digestive properties of lotus root starch were investigated. The results revealed that a combination of cold plasma and microwave treatments significantly affected the morphology of starch granules and reduced the relative crystallinity of starch compared with a single treatment. However, no changes were found in the chemical functional groups of starch after single or combined treatments. Additionally, the amylose content, amylopectin branch chain length distribution, solubility, and swelling power of the starch significantly varied depending on cold plasma treatment duration and microwave power. Furthermore, the treated starch showed lower peak viscosity and higher pasting temperature than the native one. Moreover, the resistant starch content significantly decreased as cold plasma treatment was prolonged and microwave power increased.

Effects of ultra-high pressure combined with cold plasma on structural, physicochemical, and digestive properties of proso millet starch.

In this study, proso millet starch was isolated and subjected to treatment with ultra-high pressure (UHP), cold plasma (CP), or their combination to modify its functional properties. The changes in structural, physicochemical, and digestive properties of proso millet starch after these treatments were investigated. The proso millet native starch granules showed irregular and polygonal shapes with a smooth surface. Treatments with CP or UHP at low pressures did not change the morphological properties or crystalline structure type of proso millet starch granules, while the treatment with UHP at 600 MPa and CP resulted in a complete gelatinization of starch. Also, UHP treatment at high pressure, followed by CP treatment, destroyed the partial crystalline region and reduced the short-range order of proso millet starch. Besides, a combination of UHP and CP treatment promoted the depolymerization of long chains in proso millet starch. Moreover, the combined treatments could enhance the resistance to high temperature and shearing and improve the pasting stability of starch. Furthermore, the combined treatment could increase the slowly digestible starch content. Therefore, the combination of UHP and CP treatment can be suggested for modifying the functional properties of proso millet starch and promoting its industrial applications.

Impact of calcium ions and degree of oxidation on the structural, physicochemical, and in-vitro release properties of resveratrol-loaded oxidized gellan gum hydrogel beads.

Oxidized gellan gum (OGG) hydrogel beads as delivery systems for resveratrol were fabricated by ionic cross-linking with calcium chloride (CaCl2). The degree of oxidation (DO) and CaCl2 concentration had significant influences on the formation and functional properties of hydrogel beads. The resveratrol encapsulation efficiency (66.43%-79.84%) and loading capacity (4.15%-5.05%) of OGG hydrogel beads were enhanced as DO increased. The hydrogel beads exhibited a uniform spherical shape as observed by scanning electron microscope. Fourier transform infrared spectroscopy analysis confirmed that hydrogen bonds and ionic interaction participated in the formation of hydrogel beads. X-ray diffraction analysis revealed that the physical state of resveratrol was changed from crystalline to amorphous form after encapsulation. Furthermore, the physical stability and antioxidant capacity evaluation demonstrated that the hydrogel bead fabricated with DO80 OGG and CaCl2 concentration of 1.0 M could provide high protection for resveratrol against degradation by environmental stresses and maintain its antioxidant capacity. The DO and CaCl2 concentrations could modulate the in-vitro release behaviors of hydrogel beads and obtain a good small intestinal-targeted release of resveratrol at high DO and medium CaCl2 concentration. These findings suggested that a promising delivery system for encapsulating bioactive ingredients can be fabricated by rational design.

Lipase-catalyzed Synthesis of Feruloylated Lysophospholipid in Toluene-Ionic Liquids and Its Antioxidant Activity.

In this study, Novozym 435-catalyzed interesterification of ethyl ferulate (EF) with phosphatidylcholine (PC) in a two-phase system consisting of an ionic liquid (IL) and toluene was optimized to prepare feruloylated lysophospholipids (FLPs). Optimum conditions for the interesterification process were found to be [Bmim][Tf2N]/toluene ratio of 1:1 (v/v), solvent volume of 4 mL, molecular sieves (4 Å) concentration of 80 mg/mL, reaction temperature of 55°C, substrate molar ratio of 5:1 (PC/EF), Novozym 435 concentration of 50 mg/mL. Under these conditions, two FLPs products (1-FLP and 2-FLP) with total conversion rate of 50.79% were obtained. Because the formation of 1-FLP was significantly higher than 2-FLP, 1-FLP was purified and characterized by LC-MS and NMR. In addition, 1-FLP showed DPPH scavenging activity comparable with those of EF and BHT. Therefore, this study provides a good method for transformation of ferulic acid to improve its solubility and promote its application as functional ingredient in the food and pharmaceutical industries.

The molecular structure, morphology, and physicochemical property and digestibility of potato starch after repeated and continuous heat-moisture treatment.

The multiscale structural, physicochemical, and digestible properties of potato starch before and after heat-moisture treatment were investigated, and further compared between repeated heat-moisture treatment (RHMT) and continuous heat-moisture treatment (CHMT). After heat-moisture treatment, there appeared partial disruption and pits on the starch granules, and the birefringence edges of HMT starch particles became blurred. Besides, the molecular weight of samples conspicuously decreased after two kinds of treatments. The crystal type of HMT starches transformed from B-type to C-type according to X-ray analysis. A decrease in the solubility and swelling power in high temperatures were identified. The pasting temperature, the gelatinization transition temperature (To , Tp , Tc ), and the slowly digestible starch (SDS) content of HMT starches were significantly higher than native potato starch, while the peak viscosity, the trough viscosity, the final viscosity, the breakdown, and the gelatinization enthalpy (ΔH) of RHMT and CHMT potato starches decreased compared to the native. RHMT potato starches displayed significantly higher relative crystallinity degree and gelatinization transition temperatures. The cooling process of RHMT in which the linkage between the recombinant amylose/amylopectin was enhanced compared with CHMT, which contributed to that RHMT potato starches exhibited greater advantages in practical applications. PRACTICAL APPLICATION: The described RHMT and CHMT starches provide new ideas for the study of modified starch. Furthermore, this study revealed the mechanism of heat-moisture processing provided some instructions to the application of RHMT potato starch.

Effects of germination followed by hot air and infrared drying on properties of naked barley flour and starch.

Naked barley grains were germinated at 25 °C for 12, 24, and 36 h, followed by hot air and infrared drying. Changes in structural, physicochemical, and functional properties of naked barley flour and starch after germination and drying were evaluated. Germinated and dried flour showed loose structure in starch granules surface. Germination and drying enhanced bulk density and water solubility of flour, while oil absorption capacity decreased. Treated barley starch showed greater water holding capacity, viscosity, and gelatinization temperature than those of native ones, and the maximum increase in water holding capacity of germinated barley was 20.25% of the native ones. Moreover, molecular weight, amylopectin long chains, and crystallinity of treated starch decreased, and the maximum decrease in the crystallinity of germinated barley was 78.36% of the native ones. Generally, germination for 24 and 36 h by infrared drying induced significant changes of flour and starch compared with hot air drying ones. Therefore, the combination of germination and infrared drying can be suggested as a promising method for modifying the properties of naked barley flour and starch to promote their application in the food industry.

Changes in structural, physicochemical, and digestive properties of normal and waxy wheat starch during repeated and continuous annealing.

Effects of repeated annealing treatments (8 cycles, 12 h each) or continuous annealing treatments (12-96 h) at 50 °C on structural, physicochemical, and digestive properties of normal and waxy wheat starches were investigated. Wheat starches retained the original crystalline structure of A-type after annealing. Annealing treatments increased crystallinity, short chain of amylopectin, viscosity, and gelatinization temperatures of starch. However, molecular weight, long chain of amylopectin, solubility, and swelling power of starch decreased after annealing. Additionally, annealing reduced the in vitro digestibility of wheat starches. The changes in properties of starch varied depending on starch type, normal or waxy, and annealing methods, repeated or continuous. The repeated annealing was found to be more effective in modification of normal wheat starch properties. However, continuous annealing efficiently modified properties of the waxy wheat starch. The obtained results may help in choosing appropriate applications of annealed wheat starches in the food industry.

Synthesis and characterization of a novel rice bran protein-cerium complex for the removal of organophosphorus pesticide residues from wastewater.

The removal of organophosphorus pesticides residues from wastewater of fruits and vegetables processing as well as other agricultural processes by a low-cost, environment-friendly, and efficient strategy is necessary. In this study, rice bran protein (RBP) was cross-linked with ceric ammonium nitrate (CAN). The results showed that the cross-linking process generated new functional groups and significantly enhanced the chemical reactivity and adsorption capacity of RBP. The RBPC showed rough and porous surface structure compared with smooth surface structure for RBP. In addition, greatest adsorption capacity of 193.0 mg/g and omethoate removal efficiency of 72.1% was achieved, and the results fitted well with Langmuir isotherm and pseudo-second order models. Moreover, Omethoate (5 mg/L) removal efficiency maintained over 60% after 5 cycles of RBPC usage. Therefore, the obtained RBPC complex can be suggested as an efficient adsorbent for the removal of pesticide residues from wastewater.

Effect of germination duration on structural and physicochemical properties of mung bean starch.

Mung bean seeds were germinated at 25 °C for 12, 24, 36, 48, 60 and 72 h. Changes in structural and physicochemical properties of mung bean starch during germination were investigated. Microscopy analysis showed germination did not change the shape of starch granules, but granules isolated from germinated mung bean starch exhibited dents surface structure compared with smooth surface of native starch. The molecular weight of starch isolated from germinated mung bean was found to be smaller than that of native ones. Although germinated mung bean showed greater crystallinity than that of native sample, the germination did not change the crystalline structure type of starch (C-type). Moreover, solubility and swelling power of starch varied depending on germination duration and testing temperature. Peak viscosity and trough viscosity slightly decreased as germination prolonged to 72 h. Furthermore, starch isolated from mung bean germinated for 12 h showed greater enthalpy (ΔH) than that of starch isolated from native sample; while, ΔH decrease as germination time prolonged from 36 to 72 h. The obtained results may help in understanding the influence of germination on functional properties of mung bean starch and choosing appropriate applications to promote utilization of mung bean starch in food industry.

Effect of protein aggregates on properties and structure of rice bran protein-based film at different pH.

Rice bran protein (RBP) aggregates were prepared by heating of RBP solution at 90 °C for 4 h at pH 2, 7, or 11 and used for preparing of packaging films. The structure and properties of RBP aggregates and RBP-based films were characterized with sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transmission electron microscopy, scanning electron microscope, differential scanning calorimetry, Fourier transform infrared spectroscopy and circular dichroism. The results showed formation of fibrillar, globular, and large molecular protein aggregates during the heating at pH 2, 7 and 11. The heat-aggregated RBP-based films exhibited lower opacity, moisture content, water solubility, and water vapor permeability than those of untreated RBP-based films. Also, improved mechanical and thermal properties were found for the heat-aggregated RBP-based films. In addition, the heat-aggregated RBP-based film at pH 11 showed homogenous and smooth surface as well as compact appearance compared with the untreated RBP-based films or heat-aggregated RBP-based film at pH 2 or 7. Furthermore, the secondary structure of heat-aggregated RBP film exhibited an increase in ß-sheet content and molecular interactions through non-covalent bonds. The obtained results indicated that formation of protein aggregates could improve physical, mechanical, and thermal properties of RBP-based film, especially at pH 11.

Effects of repeated and continuous dry heat treatments on properties of sweet potato starch.

The influence of repeated and continuous dry heat treatments on structural, physicochemical, and digestive properties of sweet potato starch was investigated. The results showed that the original A-type crystallinity of sweet potato starch remained unchanged after dry heat treatments. The light transmittance, gelatinization temperature, and pasting temperature of sweet potato starch increased; while the pasting viscosities, swelling power, and solubility decreased after dry heat treatments. Relative crystallinity, solubility, swelling power, light transmittance, and thermal parameter values (To, Tp, Tc, ΔT) were found to be significantly higher for the continuous dry heat (CDH) treated starch than those of the repeated dry heat (RDH) treated starch after treatment for the same duration. However, CDH treated starch samples showed lower paste viscosity and digestibility than those of RDH treated samples after treatment for the same duration. In addition, the CDH treatment highly influenced the structure of starch granule surface compared with the RDH treatment. Generally, it can be concluded that RDH treatment highly influenced structural, physicochemical, and digestive properties of sweet potato starch compared with CDH treatment.