Effects of repeated treatment on the properties of rice stem extract using subcritical water, ethanol, and their mixture

Abstract

Rice stem was repeatedly treated 3 times with subcritical water, ethanol, and 75% (v/v) ethanol in different orders at 230ºC for 5 min during each treatment step to extract its constituents. The obtained extracts were subjected to an analysis of their yield, carbohydrate content, phenolic content, radical scavenging ability, color, and UV absorption spectra. The highest total carbohydrate and phenolic contents were obtained by treatment with subcritical water, and with subcritical ethanol after pre-treatment with subcritical water, respectively. However, the extract with the highest radical scavenging ability was obtained by treatment with subcritical 75% (v/v) ethanol as the 1st treatment.

Glycerol as Alternative Co-Solvent for Water Extraction of Polyphenols from Carménère Pomace: Hot Pressurized Liquid Extraction and Computational Chemistry Calculations

“…However, high water temperatures (≥120 • C) significantly affect the chemical composition of the extracts due to polyphenol hydrolysis and formation of toxic compounds (Maillard compounds such as hydroxymethylfurfural, HMF) [46,47]. Co-solvents such as ethanol reduce the solvent polarity which can explain the significant improvement of polyphenols recovery and the considerable reduction in sugar extraction and HMF formation [48][49][50][51][52]. Glycerol, however, has been shown to be a better co-solvent than ethanol to recover polyphenols in conventional extractions; as far as we are aware there is no reported application of water-glycerol mixtures in HPLE.…”

Distribution and Conversion of Polycyclic Aromatic Hydrocarbons during the Hydrothermal Treatment of Sewage Sludge

“…HT acts as an innovative technology, transforming biomass into a highly carbonaceous product (biochar), which opens up a new idea for the transformation of plentiful waste biomass into innovative materials as soil amendments and nutrient conservation that can be used as agricultural applications. The biomass materials including rice stem, 5 paper sludge, 6 lignocellulosic biomass, 7 wheat straw, 8 green waste, 9 water hyacinth, 10 and loblolly pine. 11 During the process of hydrothermal treatment, the decomposition process of waste biomass includes hydrolysis of the organic matrix, followed by the loss of function, such as dehydration, decarboxylation, recondensation, and aromatization.…”

“…Hence, the penetration of the extractant into the steam matrix was accelerated and the solubility of organic compounds of biomass was enhanced. 5,15 generally promotes ion chemistry and suppresses free-radical reactions, which strengthens the bond cleavage of hydrogen bonds, particularly hydrolysis. Furthermore, the radical polymerization is suppressed by saturation of organic compounds via the donation of hydrogen ions; organic solvents are more powerful in this effect.…”

“…HT acts as an innovative technology, transforming biomass into a highly carbonaceous product (biochar), which opens up a new idea for the transformation of plentiful waste biomass into innovative materials as soil amendments and nutrient conservation that can be used as agricultural applications. The biomass materials including rice stem, paper sludge, lignocellulosic biomass, wheat straw, green waste, water hyacinth, and loblolly pine …”

“…During the process of hydrothermal treatment, the decomposition process of waste biomass includes hydrolysis of the organic matrix, followed by the loss of function, such as dehydration, decarboxylation, recondensation, and aromatization. , Under subcritical conditions, water is still maintained in the liquid phase and acts as a nonpolar solvent, which greatly reduces its dielectric constant, surface tension, and viscosity, thereby weakening the hydrogen bonding network of water molecules. Hence, the penetration of the extractant into the steam matrix was accelerated and the solubility of organic compounds of biomass was enhanced. , The subcritical water generally promotes ion chemistry and suppresses free-radical reactions, which strengthens the bond cleavage of hydrogen bonds, particularly hydrolysis. Furthermore, the radical polymerization is suppressed by saturation of organic compounds via the donation of hydrogen ions; organic solvents are more powerful in this effect. , Singh et al and Celikbag et al have reported that the solubility of organic contaminants in solution increased when adding organic solvent (such as ethanol) as additives, in comparison with the single solution.…”