Polymer colloidal motors with photodynamic-regulated propulsion.

Artificial colloidal motors capable of converting various external energy into mechanical motion, have emerged as attractive photosensitizer (PS) nanocarriers with good deliverability for photodynamic therapy. However, photoactivated 3O2-to-1O2 transformation as the most crucial energy transfer of the photodynamic process itself is still challenging to convert into autonomous transport. Herein, we report on PS-loaded thiophane-containing semiconducting conjugated polymer (SCP)-based polymer colloidal motors with asymmetric geometry for photodynamic-regulated propulsion in the liquid. The asymmetrical presence of the SCP phases within the colloidal motors would lead to significant differences in the 3O2-to-1O2 transformation and 1O2 release manners between asymmetrical polymer phases, spontaneously creating asymmetrical osmotic pressure gradients across the nanoparticles for powering the self-propelled motion under photodynamic regulation. This photoactivated energy-converting behavior can be also combined with the photothermal conversion of the SCP phases to create two energy gradients exerting diffusiophoretic/thermophoretic force on the colloidal motors for achieving multimode synergistic propulsion. This unique motile feature endows the light-driven PS nanocarriers with good permeability against various physiological barriers in the tumor microenvironment for enhancing antitumor efficacy, showing great potential in phototherapy.

Sunlight-triggered prebiotic nanomotors for inhibition and elimination of pathogen and biofilm in aquatic environment.

Pathogen contamination in drinking water sources causes waterborne infectious diseases, seriously threatening human health. Nowadays, stimuli-responsive self-propelled nanomotors are appealing therapeutic agents for antibacterial therapy in vivo. However, achieving water disinfection using these nanobots is still a great challenge. Herein, we report on prebiotic galactooligosaccharide-based nanomotors for sunlight-regulated water disinfection. The nanomotors can utilize galactooligosaccharide-based N-nitrosamines as sunlight-responsive fuels for the spontaneous production of antibacterial nitric oxide. Such a solar-to-chemical energy conversion would power the nanomotors for self-diffusiophoresis, which could promote the diffusion of the nanomotors in water and their penetration in the biofilm, significantly enhancing the inhibition and elimination of the pathogens and their biofilms in aquatic environments. After water treatments, the prebiotic-based residual disinfectants can be selectively utilized by beneficial bacteria to effectively relieve safety risks to the environment and human health. The low-energy-cost, green and potent antibacterial nanobots show promising potential in water disinfection.

Characteristics of meat flavoring prepared using hydrolyzed plant protein mix by three different heating processes.

Meat flavoring was prepared using mainly enzymatic hydrolysate of plant protein mix, VB1, cysteine, and glucose by three heating processes, including A (80 °C-140 min), B (two-stage, 80 °C-30 min/120 °C-30 min), and C (120 °C-40 min). The A-, B-, and C-heated samples exhibited the strongest fatty and weakest meaty, the strongest meaty and kokumi, and the strongest roasted and bitterness characteristics, respectively. PLS-DA for free amino acids with TAVs and that for SPME/GC-MS results with GC-O and OAVs, suggested three amino acids and eight flavor compounds contributed significantly in differentiating taste or aroma attributes of the three heated samples. Molecular weight distribution and degree of amino substitution suggested 1-5 kDa peptides contributed to kokumi taste. Overall, C- and A-heating exhibited the highest rates in Maillard reaction and lipid oxidation, respectively, while those of B heating were between these two heating processes and responsible for better flavor of meat flavoring.

Organic nanomotors: emerging versatile nanobots.

Artificial nanomotors are self-propelled nanometer-scaled machines that are capable of converting external energy into mechanical motion. A significant progress on artificial nanomotors over the last decades has unlocked the potential of carrying out manipulatable transport and cargo delivery missions with enhanced efficiencies owing to their stimulus-responsive autonomous movement in various complex environments, allowing for future advances in a large range of applications. Emergent kinetic systems with programmable energy-converting mechanisms that are capable of powering the nanomotors are attracting increasing attention. This review highlights the most-recent representative examples of synthetic organic nanomotors having self-propelled motion exclusively powered by organic molecule- or their aggregate-based kinetic systems. The stimulus-responsive propulsion mechanism, motion behaviors, and performance in antitumor therapy of organic nanomotors developed so far are illustrated. A future perspective on the development of organic nanomotors is also proposed. With continuous innovation, it is believed that the scope and possible achievements in practical applications of organic nanomotors with diversified organic kinetic systems will expand.

Characterization of Volatile Flavor Compounds in Dry-Rendered Beef Fat by Different Solvent-Assisted Flavor Evaporation (SAFE) Combined with GC-MS, GC-O, and OAV.

To comprehensively understand the volatile flavor composition of dry-rendered beef fat, solvent-assisted flavor evaporation (SAFE) with four extraction solvents (dichloromethane, pentane, ethyl ether, and methanol) combined with gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactormetry (GC-O) were performed. GC-MS analysis found 96 different volatile compounds in total using the four extraction solvents. According to the GC-MS results and the heat map and principal component analysis (PCA), most of the volatile compounds resulted from dichloromethane and pentane extraction, followed by ethyl ether. Methanol extraction found a few volatile compounds of higher polarity, which was supplementary to the analysis results. Moreover, GC-O analysis found 73 odor-active compounds in total using the four extraction solvents. The GC-O results found that pentane and dichloromethane extraction had a significantly larger number of odor-active compounds than ethyl ether and methanol extraction. This indicated that pentane and dichloromethane were more effective solvents for the extraction of odor-active compounds than the other two solvents. Finally, a total of 15 compounds of odor-active values (OAVs) ≥ 1 were determined to be the key aroma compounds in the dry-rendered beef fat, including 2-methyl-3-furanthiol, 3-methylthiopropanal, (E,E)-2,4-nonadienal, 12-methyltridecanal, and 1-octen-3-one.

Efficient molasses utilization for low-molecular-weight poly-γ-glutamic acid production using a novel Bacillus subtilis stain.

BACKGROUND: Poly-γ-glutamic acid (γ-PGA) is a biopolymer and has various applications based on its biocompatibility, non-toxicity, and edibility. Low-molecular-weight (Mw)-γ-PGA has promising applications in agriculture and pharmaceuticals. It is traditionally produced by enzymatic hydrolysis. Cost-effective bioproduction of low-Mw-γ-PGA is essential for commercial application of γ-PGA. RESULTS: Bacillus subtilis 242 is a newly isolated low-Mw-γ-PGA-producing strain. To develop cost-effective production of γ-PGA using this newly isolated strain, cane molasses and corn steep liquor were used to produce γ-PGA. The concentration of cane molasses was optimized and 100 g/L cane molasses resulted in high γ-PGA production. The effects of yeast extract and corn steep liquor on γ-PGA yield were investigated. High concentration of γ-PGA was obtained in the medium with corn steep liquor. A concentration of 32.14 g/L γ-PGA was achieved in fed-batch fermentation, with a productivity of 0.67 g/L/h and a percentage yield (gγ-PGA/gglutamate) of 106.39%. The Mw of γ-PGA was 27.99 kDa. CONCLUSION: This study demonstrated the potential application of B. subtilis 242 for cost-effective production of low-Mw-γ-PGA from cane molasses.

Jasmonic Acid-Treated Cotton Plant Leaves Impair Larvae Growth Performance, Activities of Detoxification Enzymes, and Insect Humoral Immunity of Cotton Bollworm.

Enhancement of plant defense by exogenous elicitors is a promising tool for integrated pest management strategy. In the present study, cotton plants were treated with different concentrations (0, 0.01, 0.1, and 1.0 mM) of the natural plant defense elicitor, jasmonic acid (JA), and defense-related indicators in the plants were then determined. The cotton bollworm larvae were fed with JA-treated cotton leaves and larvae performances were discussed in terms of larvae relative growth rate (RGR), larval duration, pupal mass, humoral immunity, and activities of a target enzyme, three detoxification enzymes and two metabolic enzymes. Research results showed that JA treatment increased the contents of gossypol and H2O2, and decreased that of the total soluble carbohydrates, and 0.1 mM JA was more powerful in the induction of defense-related parameters. As a consequence, cotton bollworm larvae reared on JA-treated cotton leaves showed slower RGR, prolonged larvae duration, and decreased pupal mass. In addition, when larvae were fed with JA-treated cotton leaves, activities of phenoloxidae (an indicator of humoral immunity) and acetylcholinesterase (AchE, a target enzyme), alkaline phosphatases (ALP), acidic phosphatase (ACP), and three detoxification enzymes, carboxylesterase (CarE), glutathione S-transferase (GST), and cytochrome P450 (P450), were all reduced compared to the control. Taken together, the results suggest that JA can be an alternative agent for pest management by delaying insect growth and inhibiting immune defense and detoxification capacity of the cotton bollworm, which may reduce the use of synthetic pesticides.

Maillard reaction chemistry in formation of critical intermediates and flavour compounds and their antioxidant properties.

The Maillard reaction involves a series of complicated reactions triggered by amino compounds reacting with reducing sugars during food processing and storage. During the Maillard reaction, a complex mixture of various Maillard reaction products (MRPs) forms, affecting the sensorial properties, stability, and nutritional and healthy value of food. Though thousands of volatile flavour compounds are identified in food from the Maillard reaction, knowledge of their formation pathway is scarce. Besides, recognition in the Maillard reaction for food antioxidant and stability mainly bases on the melanoidins. This review discusses progress in the Maillard chemistry of the critical intermediates of Amadori and α-dicarbonyl compounds in food flavour formation. In particular, it summarizes formation pathway of over 100 flavour compounds and the antioxidant activities of the individual intermediates and flavour compounds. Furthermore, complications and challenges in controlling formation of food flavor without the adverse effects are discussed based on the Maillard chemistry.

Aroma compounds identified in cooked meat: A review.

Early reviews focused on volatile compounds in cooked meat or meat products by GC-MS analysis. However, actually only a small number of odor-active activities, i.e., odorants, play roles in meat aroma. This review summarized in total 332 odorants identified in thermally cooked meat species (e.g., stewed pork) in the recent 40 years by GC-O through the search of relevant literatures. They included l57 compounds from the lipid degradation, 98 compounds from the Maillard reaction, 18 compounds from the interaction of the lipid degradation and the Maillard reaction (lipid-Maillard interaction), and 59 compounds from other sources, while the formation mechanisms are discussed based on the recent developments. Overall, the aliphatic aldehydes had the greatest number, followed by sulfur-containing compounds, nitrogen-containing heterocyclic compounds, oxygen-containing heterocyclic compounds, ketones, alcohols, etc. The frequently potent odorants in different cooked meat species are the short-chain aliphatic aldehydes of C6-C10 carbons and 1-oceten-3-ol (or 1-octen-3-one) and sulfur-containing or nitrogen-containing heterocyclic compounds. PLS-DA analysis suggested variation of odorants among the cooked beef, pork, poultry, and sheep was more due to the lipid degradation than the Maillard reaction, and marginally due to the lipid-Maillard interaction. This review can be used as guidance in improving flavor of cooked meat and meat flavorings.

Effect of deacetylated konjac glucomannan on heat-induced structural changes and flavor binding ability of fish myosin.

This work investigated the effects of deacetylated konjac glucomannan (DKGM) on heat-induced structural changes and flavor binding in bighead carp myosin. DKGM could cross-link with fish myosin to form a thermostable complex and improve the gel strength of myosin. The incorporation of DKGM increased the surface hydrophobicity and total sulfhydryl content of heat-induced myosin. Increasing DKGM concentrations resulted in a decrease in the absolute zeta potential and a continuous increase in particle size. DKGM addition significantly reduced the α-helical content of myosin with a concomitant increase in ß-sheet, ß-turn, and random coil content. The binding abilities of myosin to flavors were significantly enhanced by increasing amounts of DKGM, attributing to the accelerative unfolding of myosin secondary structures and the exposure of additional hydrophobic and thiol binding sites. Increased numbers of available hydroxyl groups after DKGM treatment could also cause an increase of flavor adsorption by hydrogen bonding.

Effects of enzymatic free fatty acid reduction process on the composition and phytochemicals of rice bran oil.

The effects of enzymatic free fatty acid reduction process (EFFARP) on the composition and phytochemicals of dewaxed and degummed rice bran oil (DDRBO) were investigated and compared with the effects observed using internal acyl acceptors. The acid value of DDRBO was effectively decreased from 16.99 mg KOH/g to approximately 0.36 mg KOH/g by EFFARP. EFFARP significantly decreased the moisture content and peroxide value of DDRBO and increased the induction period. The Sn-2 fatty acid comoposition of DDRBO after EFFARP was very reaching the total fatty acid composition. EFFARP significantly increased the triacylglycerol content compared to the control, while the oryzanol content was not obviously affected. The contents of free sterol, and total tocopherol and tocotrienol were increased slightly by EFFARP compared to the control. When conducted under vacuum with added nitrogen, EFFARP shows great application potential in the edible oil industry.

A Versatile SERS Sensor for Multiple Determinations of Polycyclic Aromatic Hydrocarbons and Its Application Potential in Analysis of Fried Foods.

Polycyclic aromatic hydrocarbons (PAHs), due to their high hydrophobicity, have low affinity for metallic SERS-active surfaces, which leads to their low SERS detection sensitivity. Various functional groups have been used to improve the affinity of metallic substrates towards the target PAHs. However, a large portion of the signals generated from the "first-layer effect" of the functionalized substrates may complicate the spectrum, leading to a distortion in the assignment of the intrinsic SERS fingerprints of PAHs. In this study, a SERS sensor composed of Au nanoparticles (AuNPs) and reoxidized graphene oxide (rGO) was developed for the simultaneous determination of 16 EPA priority PAHs. The synthesis of the rGO/AuNP substrate can be realized without a complicated modification process. All the 16 PAHs could be identified based on their characteristic peaks in the presence of the composited substrate, with estimated LOD as low as 0.2-2 ng·mL-1. The binary linear regression was optimized as the fitting model for all PAHs except for benzo(k)fluoranthene, with the linear correlation coefficient ranging from 0.9889 to 0.9997. Based on the developed SERS substrates and sample pretreatment, the characteristic SERS peaks of four PAHs in Chinese traditional fried food (youtiao) were identified without any background interference. The whole detection process only takes approximately 15 minutes. The results demonstrate the potential of the multicomponent on-field detection of PAHs.

Characterization of initial reaction intermediates in heated model systems of glucose, glutathione, and aliphatic aldehydes.

To understand the effect of lipid degradation on Maillard formation of meaty flavors, initial reaction intermediates in model systems of glucose-glutathione with hexanal, (E)-2-heptenal, or (E,E)-2,4-decadienal were identified by HPLC-MS and by NMR. Besides Amadori compounds, hemiacetals and thiazolidines via addition of sulfhydryl to carbonyl or to the conjugated olefinic bond were found. Concentrations of all intermediates increased with reaction time while degradation of the intermediates with a glutathione moiety helped formation of thiazolidines with cysteinylglycine. The unsaturated aldehydes (E)-2-heptenal and (E,E)-2,4-decadienal exhibited high reactivity against glucose for glutathione, yielding higher levels of intermediate compounds than from glucose. Heating prepared intermediates reversibly released the original aldehydes, which caused various compounds formed by retro-aldol, oxidation, etc. to react with H2S and NH3. Among them, formation pathways including 3-nonen-2-one, 2-hexanoylfuran, and six dialkylthiophenes (e.g., 2-ethyl-5-(1-methylbutyl)thiophene) were proposed for the first time.

Ionic-liquid-stabilized fluorescent probe based on S-doped carbon dot-embedded covalent-organic frameworks for determination of histamine.

An ionic-liquid-stabilized fluorescent probe for histamine is described. Sulfur-doped carbon dots (S-CDs) were incorporated into a covalent organic framework (COF) that was prepared from 1,3,5-triformylphloroglucinol and 2,5-dimethyl-p-phenylenediamine by one-pot hydrothermal polymerization in the dark. The blue fluorescence of the S-CDs (with excitation/emission maxima at 350/440 nm) is enhanced (compared to undoped CDs) due to element doping by ionic-liquid modification. The COF is resistant to acids, bases, and boiling water. The fluorescence of the probe is statically quenched by histamine, and quenching follows the Stern-Volmer equation. The normalized fluorescence of the probe drops in the 10 to 1000 µg kg-1 histamine concentration range, and the limit of detection is 5.3 µg kg-1. The probe was successfully applied to the analysis of wine and fermented meat products. The recoveries from spiked samples range between 84.6 and 115.3%. The method is selective, sensitive, stable and repeatable. The mechanisms of the fluorometric response and molecular recognition were explored. Graphical abstractSchematic presentation of ionic-liquid-stabilized fluorescent probe based on S-doped carbon dot-embedded covalent organic framework for determination of histamine. The ionic liquid [VBIm][BF4] reacts with MPTS-modified carbon dots to enhance the fluorescence signal for analyte recognition.

Emulsifying Properties of Polysaccharide Conjugates Prepared from Chin-Brick Tea.

Chin-brick tea polysaccharide conjugates (TPC-C) were prepared to study their emulsion capabilities. Interfacial tension and the effects of some factors, such as storage time, metal ion concentrations (Na+, Ca2+), pH (2.0-8.0), and heat treatment (70-100 °C) on the emulsions stabilized by TPC-C were studied. The interfacial tension of TPC-C (10.88 mN/m) was lower than that of gum arabic (15.18 mN/m) at a concentration of 0.08%. As the TPC-C concentration increased from 0.1 to 3.0 wt %, the mean particle diameter (MPD) (d32) of emulsions stabilized by TPC-C decreased from 1.88 to 0.16 µm. Furthermore, at a concentration of 0.5 wt % or higher, the MPD (d32) of emulsions stabilized by TPC-C at 25 and 60 °C for 10 days was between 0.20 and 0.50 µm. In the tested pH conditions from 2.0 to 8.0, the MPD (d32) of emulsions stabilized by 2.0 wt % TPC-C was less than 0.20 µm. At Na+ concentration conditions between 0.10 and 0.50 mol/L, the MPD (d32) of emulsions was between 0.19 and 0.20 µm, and the zeta potential values varied from -34.10 to -32.60 mV. However, with an increasing Ca2+ concentration from 0.01 to 0.05 mol/L, the MPD (d32) of emulsions was between 0.20 and 21.65 µm, and the zeta potential raised sharply from -34.10 to -28.46 mV. The emulsions stabilized by TPC-C have a decent storage stability after a high-temperature heat treatment. Overall, tea polysaccharide conjugates strongly stabilized the emulsions, which support their new application as natural emulsifiers.

Effects of Tea-Polysaccharide Conjugates and Metal Ions on Precipitate Formation by Epigallocatechin Gallate and Caffeine, the Key Components of Green Tea Infusion.

The mechanism of tea-infusion precipitation is not clear. Epigallocatechin gallate (EGCG) and caffeine (CAF) are the core components of green tea infusion precipitate. The critical precipitation concentration ( CCPC) of EGCG-CAF mixed aqueous solutions was assayed through a turbidity assay performed at 25 °C and verified by a differential-scanning calorimeter (DSC) for reliability. Different concentrations of the green tea polysaccharide conjugate fraction (gTPC-D), with a molecular weight of 2.32 × 105 Da, and of metal ions (K+, Mg2+, Ca2+, and Al3+) were respectively introduced into the mixed solution to study their effects on CCPC. On the basis of the changed CCPC, the clarification-precipitation phase diagrams of the mixed aqueous solutions were constructed. By calculating the integral area of the clarification phase, it was determined that the four metal ions and gTPC-D could accelerate precipitate formation with a dose-response relationship; among the metal ions, the effect of Al3+ is the strongest, followed by that of Ca2+.

Formation mechanism of aroma compounds in a glutathione-glucose reaction with fat or oxidized fat.

Glutathione and glucose with or without chicken fat/oxidized chicken fat were thermally reacted for generation of stewed meat-like aroma, where 42 sulfur-containing odorants were identified by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O). The observed effects or interactions on meat flavor formation due to the fats were similar to previous reports of cysteine-reducing sugar reactions. Carbohydrate module labeling approach demonstrated ten alkyl chain compounds were indeed resulted from the lipid degradation-Maillard reaction interactions, whereas the fats had little effect on formation pathways of compounds only derived from the Maillard reaction. Formation pathways of 26 potent aroma compounds were proposed, particularly, involving two benzene derivatives and seven complex thiophenes. Notably, it was found for the first time just 2-ethylthiophene could result from both an intact skeleton of glucose and the lipid degradation product of 2,4-hexadienal, and the carbohydrate modules methylglyoxal and hydroxyacetone could arise from the glutamic acid of GSH.

Rapid and sensitive detection of acrylamide in fried food using dispersive solid-phase extraction combined with surface-enhanced Raman spectroscopy.

A rapid, reliable, and quantitative method to determine acrylamide content in fried food based on surface-enhanced Raman spectroscopy (SERS) by re-oxidized graphene oxide/Au nanoparticle composites and dispersive solid-phase extraction has been proposed. The peak at △v = 1478 cm-1 was selected as the characteristic peak of acrylamide for quantitation. Sufficient linearity was obtained in the concentration range of 5-100 µg·kg-1 (R2 = 0.983). The limits of detection and quantification in fried food were 2 and 5 µg·kg-1, respectively. The recovery rates for acrylamide were 73.4-92.8% with coefficients of variation less than 4.2%, and the long-term stability of the substrates was approximately 180 days at 4 °C. The results of detection using the proposed method were consistent with those obtained by LC-MS/MS, while the measurement time was reduced to 9.5 min per sample. The study also demonstrates that this method can potentially be used for acrylamide detection in the field.

Meat flavor generation from different composition patterns of initial Maillard stage intermediates formed in heated cysteine-xylose-glycine reaction systems.

Volatile compounds formed in model reactions involving synthesized initial Maillard intermediates Gly-Amadori and [13C5]-2-threityl-thiazolidine-4-carboxylic acids ([13C5]-TTCA) in different molar ratios and free cysteine and glycine were investigated by solid-phase microextraction/gas chromatography-mass spectrometry and gas chromatography-olfactometry. The 1:1 ratio composition pattern provided the highest yields of all the sulfur-containing compounds, the potent meaty flavors or their 13C-labeled/unlabeled fractions, indicating a moderate level of glycine relative to cysteine was optimum for maximally yielding meaty flavors in complex meat-like Maillard systems containing cysteine as well as glycine. In addition, the 1:1 ratio composition led to formation of 13C-labeled molecules of some key meaty flavors e.g. 2-furanthiol representing over 70%, indicating TTCA/glycine reaction was better than Gly-Amadori/cysteine to yield meaty flavors. Formation pathways of twenty-nine flavors were elucidated based on the detected isotope distribution patterns. In particular, 2-methyltetrahydrothiophen-3-one, 3-thiophenethiol, 2-ethylthiophene, 2,5-dimethylthiophene, and 5-methylthiophene-2-carboxaldehyde involved a new formation pathway. Thiophene-2-carboxaldehyde and 2-methylthieno[3,2-b]thiophene showed two formation pathways.

Aroma Compounds in Chicken Broths of Beijing Youji and Commercial Broilers.

The unique flavor of Beijing Youji (BJY) chicken broth compared with that of commercial broilers (CB) was investigated by solvent-assisted flavor evaporation combined with AEDA/GC-O (aroma extract dilution analysis of gas chromatography-olfactometry), quantitation, and aroma recombination. A total of 71 odorants with almost the same major odorants (≥10 ng/g broth) were found by GC-O in both BJY and CB broths. However, BJY broth had thirty-two more extra odorants than CB broth, indicating the rich fragrance of the former. Aroma recombination and omission experiments demonstrated that 21 versus 17 odorants (with OAV ≥ 1) contributed significantly to BJY and CB broth aromas, respectively. Those key odorants mainly included sulfur-containing compounds and aliphatic aldehydes, such as 2-methyl-3-furanthiol, 3-(methylthio)propanal, ( E, E)-2,4-decadienal, etc. Furthermore, composition analysis of the meat suggested that the better flavor, with rather more odorants, of BJY broth is probably due to higher contents of polyunsaturated fatty acids and water-soluble flavor precursor, including ribose, cysteine, thiamine, etc., present in the BJY meat.