Four new heterometallic coordination complexes, namely, {[Zn4Ln2(imdc)4(SO4)(H2O)8]·4H2O}n [Ln = Nd (1), Sm (2), Eu (3), Gd (4); H3imdc = imidazole-4,5-dicarboxylic acid], were hydrothermally synthesized by the reactions of Ln2O3 with imidazole-4,5-dicarboxylic acid and ZnSO4·7H2O and characterized by single-crystal X-ray diffraction, infrared spectroscopy (IR), elemental analysis (EA), thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD). The single-crystal X-ray diffraction analyses reveal that these polymers are isostructural and possess an interesting 3D pillar-layered architecture with 424·64 topology, in which 2D layers constructed by alternately arranged 1D right-/left-handed helical chains of [Zn2(μ5-imdc)]n bridged via dimeric Eu2 units are pillared by μ2-SO42− and μ3-imdc3− anions. The liquid fluorescence of compounds 1–3 at room temperature shows that these complexes are very good chemosensors for I− ion, and the response of the sensor is based on fluorescence quenching of Zn–Ln MOFs by iodine ions.

•The purity of pectin was influenced by the turbid particles.•The turbidity of the extract was caused by the turbid particles.•The turbid particles were characterised to be calcium oxalate dihydrate.This paper was aimed at characterising the insoluble substances (IS) responsible for the turbidity of the extract and impurity of the resulting pectins. Results showed that the IS caused a significant increase in the turbidity of the extract. The IS had bi-pyramidal shapes under the SEM observation. The observed XRD peaks for the IS were similar to those of calcium oxalate dihydrate (COD). Moreover, the IS consisted of mainly oxalate and calcium. Results from the present study indicate the IS is COD. The influence of the IS on the purity of pectin was also studied. The presence of the IS in the pectins indicated the IS can precipitate with pectins during the alcohol precipitation, thereby contaminating the resulting pectins.

Ultrafiltration and gel chromatography were used to isolate caramel colour melanoidins, and elemental analysis and pyrolysis-GC/MS was used to analyze the characteristic of glucose–ammonium sulfite caramel colour melanoidins of various molecular weights. Results indicated that furfuran was the main skeleton of glucose–ammonium sulfite caramel colour melanoidins. And 5-hydroxymethyl-2-furaldehyde might be one of the origins of melanoidins skeleton which was formed via aldol condensation. A proposed mechanism on the formation of glucose–ammonium sulfite caramel colour melanoidins might be that bi-furan derivatives were formed after aldol condensation (part A), and sulfite ion could connect with carbon atom of formyl group, and amidolinks might be formed between aldehyde of furfuran and nitrogen atoms (part B). At last, parts A and B polymerized and formed the possible structure of the glucose–ammonium sulfite caramel colour melanoidins. And the formed melanoidins have a significant radical-scavenging activity, and complex effects on MDA-MB-231 cells survival.Highlights► Furfuran is the main skeleton of glucose–ammonium sulfite caramel colour melanoidin. ► Side links of glucose–ammonium sulfite caramel colour melanoidins contain amidolinks. ► Glucose–ammonium sulfite caramel colour has significant radical-scavenging activity. ► Effects of glucose–ammonium sulfite caramel colour on MDA-MB-231 cells survival are complex.

Effects of ultrasound on pH, intermediate products, browning, glycin and glucose contents, reducing power, and antioxidant activity of a glycin–glucose solution were examined. Results showed that the ultrasonic treatment at the intensity of 17.83 W/cm2 for 50 min resulted in the increases of the solution’s absorbance at 294 and 420 nm and the antioxidant activity from approximately 0% to 2.40%, 1.19%, and 18.62%, respectively. At the same time, 21% reduction in glycin and 92% in glucose were observed. Gas chromatography/mass spectrum analysis showed that the ultrasonic treatment induced a Maillard reaction in the model system producing substances including 2,5-dimethyl-pyrazine, trimethyl-pyrazine, (Z)-9-octadecenamide, 1,2-benzenedicarboxylic acid, and mono (2-ethylhexyl) ester. This study indicated that ultrasound, especially at higher intensities, could potentially be employed as a means to promote the Maillard reaction in the glycin–glucose solution.

Effects of pulsed electric field (PEF) on glycin and glucose content, browning value, and antioxidant activity of a glycin–glucose solution were explored. Results showed that at PEF intensity of 40 kV/cm, the solution’s absorbance at 420 nm was significantly increased from 0 to approximately 0.17 after 7.35-ms treatment. The temperature of PEF-treated samples was overall lower than 40 °C. It was also detected that the antioxidant activity of treated sample was increased to 39.36%. Moreover, 13.09% glycin and 50.76% glucose were consumed during the Maillard reaction in this experiment. This study indicates that pulsed electric field treatment, especially with higher intensity over 30 kV/cm, is a promising method to significantly promote the Maillard reaction in glycin–glucose solution.

Effects of pulsed electric field treatment on browning intensity, antioxidant activity, protein patterns and chemical structure of the bovine serum albumin–dextran copolymer were investigated. Results showed Maillard reaction between bovine serum albumin and dextran was significantly accelerated when the electric field intensity was higher than 10 kV/cm, which was proved by changes in A294, browning, antioxidant activity and electrophoresis tests. At the same time, pronounced changes of chemical structure were found by circular dichroism test. The α-helix, β-sheet, β-turns and random coil were changed from approximately 42.6%, 1.9%, 17.5% and 33.9% to 14.5%, 33.0%, 21.2% and 30.2%, respectively, after treatment at 20 kV/cm for 7.35 ms. All data indicated that pulsed electric field was a means to promote Maillard-based copolymerisation.

Five anthraquinones including aurantio-obtusin, 1-desmethylaurantio-obtusin, chryso-obtusin, obtusin, and 1-desmethylchryso-obtusin were isolated and purified by high-speed counter-current chromatography (HSCCC) and semi-preparative high-performance liquid chromatography (HPLC) from Cassia tora L. Preparative HSCCC with a two-phase solvent system composed of n-hexane–ethyl acetate–methanol–water (11:9:10:10, v/v/v/v) was successfully performed by increasing the flow rate of the mobile phase from 1.5 to 2.5 ml/min after 220 min. Consequently, 35.8 mg aurantio-obtusin, 21.6 mg obtusin, 9.3 mg 1-desmethylchryso-obtusin and one partially purified peak fraction (80.6 mg, containing chryso-obtusin and 1-desmethylaurantio-obtusin) were obtained from 300 mg of the crude extract. Then the partially purified fraction was further separated by reversed-phase semi-preparative HPLC, which recovered 24.6 mg 1-desmethylaurantio-obtusin and 51.9 mg chryso-obtusin. The purity of aurantio-obtusin, 1-desmethylaurantio-obtusin, chryso-obtusin, obtusin, and 1-desmethylchryso-obtusin was 98.3, 98.7, 99.5, 97.4 and 99.6%, respectively, as determined by HPLC. The structures of five anthraquinones were identified by UV, MS, 1H NMR.

The Maillard reaction always occurs during the thermal processing of dairy products, which significantly influences their quality. In the present study, the initial stages of a glucose-proline model system were investigated in water and different types of buffer solutions. Results showed that phosphate buffer accelerated the reversible degradation of the initial stages of the reaction. The proposed catalysis mechanism was that hydrogenous and dihydric phosphate radical anions simultaneously accepted and donated protons for the conversion of the intermediates into N-glycosylamine. The catalysis mechanism was confirmed via testing and no reducing of hydrogenous and dihydric phosphate radical anions was observed during the reaction. Moreover, both N-(1-deoxy-d-fructos-1-yl)proline and its degradation compounds were analyzed. Results showed that degradation of N-(1-deoxy-d-fructos-1-yl)proline to form 5-hydroxymethyl-2-furaldehyde and formic acid was also accelerated by phosphate buffer. An interesting phenomenon was that citrate decreased 5-hydroxymethyl-2-furaldehyde formation, which might be because Strecker-type degradation occurred more easily than 1,2-enolization reaction in citrate buffer solution. However, this hypothesis has not been confirmed, and element label experiments should be carried out in the future.