La3+ and mixed-rare earth magnetic chitosan beads (MCLB and MCLRB) were successfully prepared for fluoride removal, respectively. The adsorbents were characterized by scanning electron microscope and magnetic response. Batch experiments were carried out to investigate the adsorbent performance based on the influence of various factors such as adsorbent dosage, contact time, initial solution pH and co-existing anions on the fluoride adsorption. Results showed that MCLB and MCLRB followed the pseudo-second-order kinetic model with the correlation coefficient value of 0.9925 and 0.9985 respectively. The adsorption process was mainly chemical adsorption. The isotherm data was well fitted both Langmuir model and Freundlich model. The adsorption capacity of the adsorbents were 20.53 and 22.35mg/g respectively. The optimum pH value for fluoride ion removal was 5.0. The effects of co-existing anions on the fluoride sorption followed the decreasing order of CO32->HCO3->SO42->NO3->Cl-. Fluoride adsorption on MCLB and MCLRB could be attributed to ion exchange between fluoride and OH groups with the FeO coordinate bond promotion. Our study revealed that MCLB and MCLRB performed strong adsorption capacity for fluoride ion. In particularly, MCLRB could be a more cost-effective adsorbent to remove fluoride from aqueous solution.

The structure and functionality of pea albumin can be described in detail as a combination of its main fractions, PA1 and PA2. PA1 and PA2 were purified from a Pea Albumin extract (PA) using size exclusion chromatography, and characterized by two-dimensional gel electrophoresis. Their secondary structure was analyzed using Fourier-Transform Infrared Spectroscopy (FTIR). The structures before and after heat treatment (90 °C, 1 & 5 min) were investigated by Small-Angle X-ray Scattering (SAXS). SAXS intensities were evaluated using high-resolution models obtained as predictions from the AlphaFold Protein Structure Database. Interfacial and foaming properties were also evaluated. Both PA1 and PA2 contained various isoforms, and PA2 displayed a high β-sheet/α-helix ratio. In solution, SAXS intensities of PA1 could be predicted by its native structure, and after heating PA1 showed limited aggregation. PA2 could be presented as a dimer, which unfolded and formed large aggregates during heating. The high-resolution models could also explain well the SAXS signal of the unfractionated PA, combining PA1 and PA2. After heating, PA2 dominated the properties of the PA mixtures. PA2 predominantly contributed to the interfacial and foaming properties of PA, in spite of both PA1 and PA2 showing adsorption at the air/water interface. Indeed, PA1 in isolation could not form a stable foam. SAXS data analyzed with high-resolution structure models allowed for an in depth understanding of the structural changes of PA1 and PA2, and provided a mechanistic understanding of the relationships between structure, composition, and technological functionality of the albumin fractions from pea.

Pea albumins are found in the side stream during the isolation of pea proteins. They are soluble at acidic pH and have functional properties which differ from their globulin counterparts. In this study, we have investigated the aggregation and structural changes occurring to pea albumins under different environmental conditions, using a combination of size-exclusion chromatography coupled with multi-angle laser light scattering (SEC-MALS) and small-angle X-ray scattering (SAXS). Albumins were extracted from a dry fractionated pea protein concentrate by precipitating the globulin fraction at acidic pH. The albumins were then studied at different pH (3, 4, 4.5, 7, 7.5, and 8) values. The effect of heating at 90 °C for 1, 3, and 5 min on their structural changes was investigated using SAXS. In addition, size exclusion of the albumins showed 4 distinct populations, depending on pH and heating conditions, with two large aggregates peaks (∼250 kDa): a dimer peak (∼24 kDa) containing predominantly pea albumin 2 (PA2), and a monomer peak of a molar mass of about 12 kDa (PA1). X-ray scattering intensities as a function of q were modeled as polydisperse spheres, and their aggregation was followed as a function of heating time. Albumins was most stable at pH 3, showing no aggregation during heat treatment. While albumins at pH 7.5 and 8 showed aggregation after heating, solutions at pH 4, 4.5, and 7 already contained aggregates even before heating. This work provides new knowledge on the overall structural development of albumins under different environmental conditions, improving our ability to employ these as future ingredients in foods.