Pretreatment of kraft lignin by deep eutectic solvent and its utilization in preparation of lignin-based phenolic formaldehyde adhesive

To improve the reactive sites of kraft technical lignin, a deep eutectic solvent (DES) composed of ZnCl2 / lactic acid was used to pretreat kraft lignin from coniferous wood. The modified and unmodified lignin were used to replace different proportions of phenol (50%, 60%, and 70%) to prepare the lignin-phenol-formaldehyde (LPF) adhesive. The phenolic hydroxyl content of DES-treated lignin increased from 3.12 wt% to 3.93 wt% and methoxy content decreased from 11.83 wt% to 6.64 wt% under optimized experimental conditions. The bond strength of LPF adhesive prepared by DES reagent activated lignin was higher than that of the control sample. When the substitution degree of modified lignin for phenol reached 70%, the bond strength of the plywood prepared by the DES-pretreated lignin was 0.79 MPa and the free formaldehyde content was 0.28%, which met the requirements of the Chinese national standard GB/T 9846 (2015). However, the viscosity was higher than the control sample, and results indicate that DES reagent modification cannot improve the viscosity of LPF resin.

Influence of phenolic acid content on the antioxidant capacity of hemicellulose from sorghum plant fractions

Recovered hemicellulose fractions from biorefineries have the potential to improve overall process economics during the production of biofuels or other high value chemicals. A common hemicellulose found in many agricultural feedstocks is arabinoxylan (AX). This work investigated the influence of ferulic and p-coumaric acids on the antioxidant capability of AX hemicellulose recovered from sorghum bran, biomass, and bagasse. Sorghum bagasse and sorghum biomass AX contained the largest quantities of bound ferulic and p-coumaric acids at 13.1 mg/100 g and 6.3 mg/100 g, respectively. Antioxidant performance showed that sorghum bagasse AX hemicellulose produced the best reducing capability, while sorghum biomass and sorghum bran AX hemicellulose performed better as free radical scavengers. A reduction in free radical scavenging, as determined by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, occurred for sorghum bagasse and sorghum biomass AX hemicellulose at higher polysaccharide concentrations, which was either caused by the solution properties of the AX hemicelluloses or DPPH reaction reversibility in the presence of phenolic compounds with methoxy content. Alternatively, H2O2 scavenging by the AX hemicellulose revealed a dose-dependent response. Although scavenging effect was reduced at higher concentrations, sorghum bagasse AX hemicellulose functioned as having the best antioxidant capacity with respect to total reducing capability.

Isolation and Characterization of Pectin from Pumpkin (Cucurbita maxima) Waste and Its Food Application

Pectin was extracted using the method of acid hydrolysis followed by ethanol precipitation at various reaction conditions. Effect of blanching prior to acid hydrolysis, acid types (hydrochloric and citric) and extraction time and temperature combinations were tested to maximize the yield of pectin and they were characterized by assessing physiochemical and functional properties. The feasibility of utilizing extracted pectin in food applications was evaluated. The yield of pectin ranged from 7.30 ± 0.07- 11.04 ±0.01% on a dry weight basis. The results suggested that the highest pectin content is in the fresh pumpkin peel extracted using 0.1 N hydrochloric acid at 80±5℃, 1.25 pH for 1 hour. Water holding capacity, oil holding capacity and emulsifying activity index of pumpkin pectin were 2.5 g/g of pectin (SD 0.46), 1.76 g/g of pectin (SD 0.10) and 0.29 (SD 0.01) respectively. In addition, the degree of esterification, equivalent weight, methoxy content and galacturonic acid content of extracted pectin were 67.64% (SD 0.89%), 978.35 (SD 69.88), 6.55% (SD 0.37%) and 66.46% (SD 1.19%) respectively. Sensory analysis revealed that there is no significant difference in spreadability, surface texture and chewiness of two types of jam prepared using pumpkin and commercial pectin. In conclusion, pumpkin pectin can be categorized as high methoxy pectin.