Structural Changes in Milled Wood Lignin (MWL) of Chinese Quince (Chaenomeles sinensis) Fruit Subjected to Subcritical Water Treatment

Abstract

Subcritical water treatment has received considerable attention due to its cost effectiveness and environmentally friendly properties. In this investigation, Chinese quince fruits were submitted to subcritical water treatment (130, 150, and 170 °C), and the influence of treatments on the structure of milled wood lignin (MWL) was evaluated. Structural properties of these lignin samples (UL, L130, L150, and L170) were investigated by high-performance anion exchange chromatography (HPAEC), FT-IR, gel permeation chromatography (GPC), TGA, pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), 2D-Heteronculear Single Quantum Coherence (HSQC) -NMR, and 31P-NMR. The carbohydrate analysis showed that xylose in the samples increased significantly with higher temperature, and according to molecular weight and thermal analysis, the MWLs of the pretreated residues have higher thermal stability with increased molecular weight. The spectra of 2D-NMR and 31P-NMR demonstrated that the chemical linkages in the MWLs were mainly β-O-4′ ether bonds, β-5′ and β-β′, and the units were principally G- S- H- type with small amounts of ferulic acids; these results are consistent with the results of Py-GC/MS analysis. It is believed that understanding the structural changes in MWL caused by subcritical water treatment will contribute to understanding the mechanism of subcritical water extraction, which in turn will provide a theoretical basis for developing the technology of subcritical water extraction.

Thermal fluctuation and conformational effects on NMR parameters in β-O-4 lignin dimers from QM/MM and machine-learning approaches

“…In water, these values are closer to the experimental ones, recently reported to be 6.94 (H C2 ), 6.65 (H C5 ) and 6.75 (H C6 ) ppm in G units in milled wood lignin of Chinese quince fruit. 68 Similar δ ( 1 H) values (between 6.7–7.1 ppm) were assigned to the ring hydrogens in guaiacyl from NMR measurements in DMSO 69 and acetone solvents. 2 Another spike in the computed 1 H NMR is 〈 δ ( 1 H)〉 in the hydroxyl group in ring B (H Oα′ ) in ethanol solvent.…”

“…The last column in Table 2 reports the intervals of known experimental δ ( 13 C) values in β-O-4 linkages between G-units 1,2,5,13,68 collected from solid-state or liquid-state NMR measurements. Our calculated chemical shifts fall in the same ranges, despite the different solvents considered here.…”

Catalytic Degradation of Lignin over Sulfonyl-Chloride-Modified Lignin-Based Porous Carbon-Supported Metal Phthalocyanine: Effect of Catalyst Concentrations

“…In this process, the degradation of lignin and the polycondensation of intermediates take place simultaneously and compete with each other. The cleavage of β-O-4 results in the reduction in the molecular weight; conversely, the formation of superpolymers or char may result in an increase in the molecular size [ 61 ]. As can be seen from Table 4 , lignin had an Mw of 66,671 g/mol and the polydispersityare value was 1.81.…”

Effect of free and bound proanthocyanidins from Chinese quince on heterocyclic aromatic amine formation and quality in fried chicken

“…The values of the mean DP of the BP were lower than the values of BP obtained in a previous study (Hamauzu & Mizuno, 2014). This may be because the catalytic effect of subcritically treated water (Wang, Qin, et al., 2021) is greater than that of H + and OH − for weak acids or bases. Subcritical water treatment may break the bonds between BP and cell walls of the quince to release proanthocyanidins.…”