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A β‐1,3‐1,4‐glucanase gene (Auglu12A) from Aspergillus usamii was successfully expressed in Escherichia coli BL21(DE3). The recombinant enzyme, reAuglu12A was efficiently purified using the one‐step nickel‐nitrilotriacetic acid affinity chromatography. The specific activity of reAuglu12A was 694.8 U/mg, with an optimal temperature of 55°C and pH of 5.0. The reAuglu12A exhibited stability at temperatures up to 60°C and within the pH range of 4.0–5.5. The reAuglu12A hydrolytic activity was increased in the presence of metal ions, especially K+ and Na+, whereas it exhibited a Km and Vmax of 8.35 mg/mL and 1254.02 µmol/min/mg, respectively, toward barley β‐glucan at pH 5.0 and 55°C. The addition of reAuglu12A significantly increased the specific volume (p < 0.05) and reduced crumb firmness and chewiness (p < 0.05) of wheat–barley sourdough bread during a 7‐day storage period compared to the control. Overall, the quality of wheat–barley sourdough bread was improved after incorporation of reAuglu12A (especially at 3000 U/300 g). These changes were attributed to the synergistic effect of acidification by sourdough and its metabolites which provided a conducive environment for the optimal action of reAuglu12A in the degradation of β‐glucans of barley flour in sourdough. This stabilized the dough structure, thereby enhancing the quality, texture, and shelf life of the bread. These findings suggest that reAuglu12A holds promise as a candidate for β‐glucanase application in the baking industry. [ABSTRACT FROM AUTHOR]

Colloidal nanoparticles in tea infusion are the link connecting micromolecular mechanism and macro‐aggregation process of tea cream formation. In order to elucidate, the kinetics mechanism of green tea nanoparticles (gTNPs) aggregation, zeta‐potentials, total average aggregation (TAA) rates, and critical coagulation concentration (CCC) in the presence of various pH and metal ions were investigated. Additionally, the effect of temperature on gTNPs aggregation was further explored. The results revealed that the TAA rate of gTNPs increased with decreasing pH values, the CCC of gTNPs increased in the order Mg2+ ≈ Ca2+ < Na+ ≈ K+. The reason was that different positive ions changed the surface electric field strength of gTNPs to a different extent. Furthermore, it was indicated that low temperature could promote gTNPs aggregation in indirect way. Low temperature promoted the binding of epigallocatechin gallate (EGCG) and caffeine, and the combination between gTNPs and EGCG–caffeine complexes weakened the stability of gTNPs resulting from reduction in electrostatic repulsion. Practical Application: Tea is a popular beverage all over the world. This research revealed the mechanism of green tea nanoparticles aggregation and laid a theoretical foundation for the regulation of tea cream formation in tea beverage. [ABSTRACT FROM AUTHOR]

By utilizing the coffee‐ring effect and microfluidic paper‐based analytical devices (µPADs), this study improved the sensitivity of the determination of norfloxacin in four different food matrices. Micro‐PADs in this study were fabricated by designing and embedding wax channels onto cellulose‐based filter paper through printing and subjecting the paper to heat to allow the wax to penetrate the paper. Determination of norfloxacin concentration in food samples was achieved by monitoring the colorimetric reaction that occurred between norfloxacin and the added iron (III) nitrate nonahydrate in 5 mM ammonia in each reaction chamber. A transition metal hydroxide was formed through this reaction that resulted in the formation of a solid precipitate to enable the antibiotic to bind to the iron molecule via coordination chemistry. This metal ion–antibiotic complex generated a visible color change. Following the colorimetric reaction, images were taken and subsequently analyzed via ImageJ to determine the relative pixel intensity that was used to infer norfloxacin concentration. The analytical sensitivity of this device was determined to be as low as 50 ppm when analyzing the inner‐ring reaction, and as low as 5 ppm when analyzing the outer coffee ring thereby allowing for an alternative cheaper, faster, and more user‐friendly method to detect norfloxacin than the conventional methods. Practical Application: This novel paper‐based microfluidic device can achieve the detection of antibiotic residues in agrifoods in a faster, cheaper, and more user‐friendly manner. [ABSTRACT FROM AUTHOR]

Grain sorghum is gaining interest for various uses as a highly sustainable crop. Kafirin is the main storage protein in grain sorghum. However, the antioxidant activities of kafirin hydrolysates have not been systematically investigated. The objectives of this study were to characterize the antioxidative hydrolysates and their ultrafiltrated fractions from sorghum kafirin using chemical assays and model systems and to identify the representative peptides. Kafirin Neutrase hydrolysates displayed promising yield and antioxidant capacity among those prepared with several different proteases. The effects of critical variables including protein substrate content, enzyme‐to‐substrate ratio, and reaction time on antioxidant production were studied. Selected hydrolysates were further fractionated through ultrafiltration and gel filtration chromatography (GFC). Medium‐sized fraction (3 to 10 kDa) revealed relatively higher total phenolic content and stronger antioxidative activities with regard to free radical scavenging activity, metal ion chelating activity, reducing power, and oxygen radical absorbance capacity. In an oil‐in‐water emulsion system, incorporation of selected fraction of hydrolysates inhibited the formation of primary and secondary oxidation products by 83.03% and 65.59%, respectively, by the end of a 14‐day incubation period. Similar oxidation inhibition effect was also observed in a ground meat system. Peptide compositions of the most promising fraction from GFC and reversed‐phase high‐performance liquid chromatography were identified using matrix‐assisted laser desorption ionization–time of flight/time of flight mass spectrometry. Practical Application: This study provided a feasible approach to produce peptide antioxidants from sorghum kafirin. The novel naturally derived antioxidants could be potentially used as alternatives or synergetic components to synthetic antioxidants in improving the oxidative stability of various food products. [ABSTRACT FROM AUTHOR]

A rapid and simple approach for visible determination of mercury ions (Hg2+) in aqueous solutions was developed based on surface plasmon resonance phenomenon using L-arginine-functionalized gold nanorods (AuNRs). At pH greater than 9, the deprotonated amine group of L-arginine on the AuNRs bound with Hg2+ leading to the side-by-side assembly of AuNRs, which was verified by transmission electron microscopy images. Thus, when Hg2+ was present in the test solution, a blue shift of the typical longitudinal plasmon band of the AuNRs was observed in the ultra violet-visible-near infrared (UV-Vis-NIR) spectra, along with a change in the color of the solution, which occurred within 5 min. After carefully optimizing the potential factors affecting the performance, the L-arginine/AuNRs sensing system was found to be highly sensitive to Hg2+, with the limit of detection of 5 nM (S/N = 3); it is also very selective and free of interference from 10 other metal ions (Ba2+, Ca2+, Cd2+, Co2+, Cs+, Cu2+, K+, Li+, Ni2+, Pb2+). The result suggests that the L-arginine-functionalized AuNRs can potentially serve as a rapid, sensitive, and easy-to-use colorimetric biosensor useful for determining Hg2+ in food and environmental samples. [ABSTRACT FROM AUTHOR]

Zein protein was extracted from the by-product corn gluten meal. The obtained zein protein was 1st hydrolyzed by 4 different proteases. The antioxidant activities of the hydrolysates or peptides were evaluated by free radical scavenging activity, metal ion chelating activity, and lipid peroxidation inhibitory capacity. Among hydrolysates produced, alkaline protease hydrolysates exhibited the highest antioxidant activity. A regression model was established by uniform design to optimize the alkaline protease hydrolysis conditions. The hydrolysates with molecular weight < 3 kDa obtained from ultrafiltration showed the highest antioxidant activities in all relevant assays. The hydrolysates with molecular weight <3 kDa were subsequently purified by gel filtration chromatography, and fraction F3 exhibited the highest antioxidant activities. Two peptides were identified from fraction F3 using LC-ESI-Q-TOF MS/MS as Pro-Phe (263.13 Da) and Leu-Pro-Phe (375.46 Da). These peptides exhibited good free radical scavenging activity and lipid peroxidation inhibitory effect. The results clearly indicated that zein protein fractions are good sources for the development of natural antioxidants for the food industry. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the removal of Cd2+ and Al3+ from aqueous solutions by an exopolysaccharide (EPS) from Lactobacillus rhamnosus E/N. The biosorption kinetics of EPS for Cd2+ and Al3+ were studied by equilibrium dialysis after incubation from 0 h to 58 h. The actual concentrations of Cd2+ and Al3+ in external solutions were measured by a fluorescence method after complexation with 8-hydroxyquinoline. Binding of metal ions by EPS was observed, with maximum adsorption after 0 to 24 and 48 to 58 h for Cd2+, and after 24 h for Al3+. The existing analytical method, involving the binding of metal ions was measured using a dialysis membrane was significantly improved in our study. This new method could be applied in future studies of this type. The results of this study demonstrate that EPS from Lb. rhamnosus E/N has a Cd2+ and Al3+ biosorption capacity. Surface adsorption of the metal ions at surface of EPS was confirmed through scanning electron microscopy. Fourier transform-infrared spectroscopy analysis suggests a role of the functional groups ─OH, C═O, and COO− from EPS in the binding of Cd2+ and Al3+ ions. [ABSTRACT FROM AUTHOR]