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The high temperature induces conformational changes in ß-glucosidase, making it inactive and limiting its application field. In this paper, the effect of trehalose on the thermostability of ß-glucosidase from low-moisture Hevea brasiliensis seeds was investigated. The results showed that the residual enzyme activities of ß-glucosidase supplemented with trehalose after high-temperature treatment were significantly higher than that of the control group. The improvement of thermostability could be explained by low-field nuclear magnetic resonance (LF-NMR) and molecular dynamics (MD) simulations at the molecular level. Moreover, adding trehalose increased the water activity and water content of ß-glucosidase, leading to a more stable conformation. Trehalose replaced some water and formed a stable network of hydrogen bonds with protein and surrounding water. The glass formed by trehalose also reduced molecular movement, thus providing good protection for enzymes.

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Inhibiting the formation of advanced glycation end products (AGEs) in the heat-processed food can reduce health risks related to diabetic complications. However, additives used for this purpose may also affect the sensory characteristics of food products. In this study, the effects of six hydrocolloids on the formation of AGEs were evaluated in the lysine-glucose model, with κ-carrageenan exhibited the highest inhibitory activity. Mechanistic investigations indicated that κ-carrageenan conjugated with the key intermediates of AGEs, namely glyoxal (GO) and methylglyoxal (MGO). Subsequently, the inhibitory effect of κ-carrageenan on AGEs formation in cakes was verified. The data showed that κ-carrageenan in cakes significantly inhibited the formation of fluorescent and non-fluorescent AGEs. In addition, analysis of cake characteristics and sensory evaluation showed that cakes with 1% (w/w) κ-carrageenan had the highest quality and overall acceptance. Overall, κ-carrageenan is an effective inhibitor of AGEs formation in heat-processed food.

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As a traditional interconnect material, silver alloy bonding wires are widely used in electronic packaging, but their propensity to vulcanize quickly has not been sufficiently addressed. The current surface anti-oxidation and anti-sulfidation treatments are often accompanied by a decline in bonding performance, which hinders the use of silver alloy bonding wires in new applications. In the present paper, we develop a new cathodic passivation treatment in a Pd-containing solution for silver bonding wires, which not only significantly improves their vulcanization resistance, but also maintains their bonding performance. The surface of the treated wires remains unaffected after vulcanization in 0.3 µg/m3 of ammonium sulfide for 60 min. Compared to a Pd-free passivation treatment, the bonding strength of the wire passivated with the Pd-containing solution improves from 0.20 to 0.27 N. XPS analysis confirms the existence of Pd on the surface of the wire. The solder ball formed an obtuse angle instead of a sharp angle on the pad, which is beneficial for bonding strength.

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In this study, structural characteristics and formation mechanism of Mesona chinensis polysaccharide (MCP)-whey protein isolate (WPI) gels including group and molecular changes, intermolecular forces, crystallinity, and moisture migration were investigated under pH shifting conditions. Results showed that MCP and WPI formed a stable gel at pH 10. The free sulfhydryl groups and surface hydrophobicity of the MCP-WPI gels increased with the increasing pH. Hydrophobic and hydrogen bond interactions were the main molecular forces involved in the MCP-WPI gels, and electrostatic interactions and disulfide bonds played a complementary role. The pH conditions evidently influenced the secondary conformational structure of MCP-WPI gels. Molecular weight and X-ray diffraction (XRD) analysis indicated the formation of a hypocrystalline complex with molecular interaction. In addition, low-field magnetometry (LF-NMR) results showed that the T2 values decreased with increasing pH, indicating that water and gel matrix had the highest interactions at pH 10.

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This work attempts to study and optimize the conditions for separating and purifying papain in aqueous two-phase systems (ATPSs). Quaternary ammonium ionic liquids (ILs, 4 wt%) were added as adjuvants to a PEG-phosphate ATPS. On the basis of single-factor experiments, a Box-Behnken design with response surface methodology (BBD-RSM) was used to optimize the purification conditions of papain in the ATPS by setting the NaH2PO4·2H2O concentration, PEG concentration and pH as independent variables and the overall desirability (OD) of the recovery rate of papain, the protein recovery rate and the purification factor as dependent variables. The following optimum conditions were determined: PEG4000 16.4 wt%, NaH2PO4·2H2O 13.7 wt%, pH 6.22, temperature 60 °C and enzyme concentration 12.0 mg/ml. Under the optimized conditions, the purification factor for the ATPS supplemented with commercial enzyme increased from 1.331 (no ILs) to 3.380 (containing 4 wt% [N2222]BF4). The total evaluation OD was 0.9979, the maximum predicted OD was 0.9994, and the deviation rate was -0.15%. Therefore, the model established in this experiment could predict the experimental value well. To verify the practical effect of the model, papain obtained from fresh papaya latex (papain crude extract) was applied to the same ATPS. The results showed that the purification factor of the ATPS with papain crude extract increased from 3.517 (no ILs) to 12.04 (containing 4 wt% [N2222]BF4). In summary, the addition of 4 wt% ILs to partially replace PEG greatly improved the purification factor for crude papain extract enriched in the phosphate phase, providing a potential method for the large-scale industrial production of papain.

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BACKGROUND: Arabica coffee is a sub-tropical agricultural product in China. Coffee undergoes a series of thermal reactions to form abundant volatile profiles after roasting, so it loses a lot of reducing sugars and amino acids. Adding carbonyl compounds with amino acids before roasting could ensure the nutrition and flavour of coffee. The technology is versatile for the development of coffee roasting process. This investigation evaluates the effects of combining maltose and lysine (Lys) to modify coffee aroma and the possibly related mechanisms. Arabica coffee was pretreated with a series of solvent ratios of maltose and Lys with an identical concentration (0.25 mol L-1 ) before microwave heating. RESULTS: It was found that the combination of maltose and Lys significantly (P ≤ 0.05) influenced quality indices of coffee (pH and browning degree). Ninety-six aromatic volatiles have been isolated and identified. Twelve volatile profiles revealed the relationship between fragrance difference and compound content in coffee. Moreover, coffee aroma was modified by a large number of volatiles with different chemical classes and character. CONCLUSION: Thus, our results suggest that the combination of reagents changed overall aroma quality through a series of complex thermal reactions, especially the ratio of Lys/maltose over 2:1. © 2017 Society of Chemical Industry.

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A simple and inexpensive aqueous two-phase affinity partitioning system using metal ligands was introduced to improve the selectivity of commercial papain extraction. Polyethylene glycol 4000 was first activated using epichlorohydrin, then it was covalently linked to iminodiacetic acid. Finally, the specific metal ligand Cu(2+) was attached to the polyethylene glycol-iminodiacetic acid. The chelated Cu(2+) content was measured by atomic absorption spectrometry as 0.88 mol/mol (polyethylene glycol). The effects on the purification at different conditions, including polyethylene glycol molecular weight (2000, 4000, and 6000), concentration of phase-forming components (polyethylene glycol 12-20% w/w and sodium sulfate 12-20%, w/w), metal ligand type, and concentration, system pH and the commercial papain loading on papain extraction, were systematically studied. Under optimum conditions of the system, i.e. 18% w/w sodium sulfate, 18% w/w polyethylene glycol 4000, 1% w/w polyethylene glycol-iminodiacetic acid-Cu(2+) and pH 7, a maximum yield of 90.3% and a degree of purification of 3.6-fold were obtained. Compared to aqueous two phase extraction without ligands, affinity partitioning was found to be an effective technique for the purification of commercial papain with higher extraction efficiency and degree of purification.

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Polyphenols are functional compounds in plants, which possess many bioactivities beneficial for humans. The aim of this study was to establish a highly efficient method for extracting polyphenol compounds from areca seeds and further to identify polyphenols and antioxidant properties of the seeds. A quadratic general rotary unitized design was used to determine the optimal extraction process. The polyphenols were identified using LC-TOF-MS. By comparison with ascorbic acid (Vc), the antioxidant activities of the ethanol extracts were evaluated using three complementary in vitro assays: inhibition of the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical-scavenging activity, hydroxyl radical-scavenging activity, and reducing ability. The two major polyphenols obtained were epicatechin and syringic acid. The ethanol extracts of areca seeds showed significantly greater antioxidant activity (p < 0.05) than Vc using the DPPH and reducing power assay, but lower ability (p < 0.05) using the hydroxyl radical assay. The results indicate that the areca seed is an excellent food material with potential antioxidant properties.

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