Pressurized Treatment Research Articles

Recent advances in pressurized hot water extraction/modification of polysaccharides: Structure, physicochemical properties, bioactivities, and applications.

Pressurized hot water, as a green and efficient physical treatment technology, has been widely utilized for the extraction and modification of polysaccharides, with the objective of enhancing the physicochemical properties and biological activities of polysaccharides applied in food systems. This article reviews the recent advances regarding the effects of pressurized hot water treatment (extraction and modification) on polysaccharide extraction rates, structure, physicochemical properties, and bioactivities. The potential modes and mechanisms of polysaccharides subjected to pressurized hot water treatment and the relevant applications of these treated polysaccharides are also thoroughly discussed. Finally, the challenges that it may encounter in commercial applications are analyzed, and the future trends in this field are envisioned. This article will be of great value for the scientific elucidation of polysaccharides treated with pressurized hot water and their potential food applications.

Corrigendum to “Preparation of spinnable mesophase pitch from pyrolyzed fuel oil by pressurized heat treatment and its application of carbon fiber” [Carbon 226 (2024) 119160

Corrigendum to “Preparation of spinnable mesophase pitch from pyrolyzed fuel oil by pressurized heat treatment and its application of carbon fiber” [Carbon 226 (2024) 119160

Pressurized microwave-assisted hydrothermal treatment with various salts for efficient production of monosaccharides from rice straw

This study proposed a two-stage pressurized microwave hydrothermal treatment with a catalyst, followed by enzymatic saccharification, as a pretreatment method for efficiently converting cellulose and hemicellulose from rice straw into glucose and xylose. The use of various inorganic salts and dilute sulfuric acid as catalysts enhances sugar production. Using 1wt% sulfuric acid as a catalyst at 150°C for 5min for the first-stage and then 180°C for 5min for the second-stage yielded the highest sugar production from rice straw compared with other inorganic salts tested. The filtrate and enzymatic saccharification solution contained a total sugar of 0.434g/g-untreated rice straw (i.e. 0.302g-glucose/g-untreated rice straw and 0.132g-xylose/g-untreated rice straw). When inorganic salts such as NaCl, MgCl2, CaCl2, and FeCl3 were used as catalysts, the highest sugar yield of 0.414g/g-untreated rice straw (i.e. 0.310g-glucose/g-untreated rice straw and 0.104g-xylose/g-untreated rice straw) was obtained when using 1wt% FeCl3 at 170°C for 5min in the first-stage and 190°C for 5min in the second-stage, with a value close to that of 1wt% sulfuric acid. These findings suggest that two-stage treatment with a catalyst is a suitable pretreatment method for the production of glucose and xylose from rice straw owing to the different hydrolysis temperatures of cellulose and hemicellulose.

Preparation of spinnable mesophase pitch from pyrolyzed fuel oil by pressurized heat treatment and its application of carbon fiber

Preparation of spinnable mesophase pitch from pyrolyzed fuel oil by pressurized heat treatment and its application of carbon fiber

A CALPHAD thermodynamic model for multicomponent alloys under pressure and its application in pressurized solidified Al–Si–Mg alloys

A CALPHAD thermodynamic model for multicomponent alloys under pressure and its application in pressurized solidified Al–Si–Mg alloys

The effect of pressurized heat treatment on the textural, flavor, nutritional, and digestive characteristics of soft-boiled and marinated eggs

The effect of pressurized heat treatment on the textural, flavor, nutritional, and digestive characteristics of soft-boiled and marinated eggs

Effect of Pressurized Hydrothermal Treatment on the Properties of Cellulose Amorphous Region Based on Molecular Dynamics Simulation

Based on Materials Studio software, a cellulose chain with a polymerization degree of 20 and several water molecules were constructed to form a cellulose amorphous region–water model. The effect of pressure on the wood properties during hydrothermal treatment was investigated to explain the changes in the macroscopic properties from a microscopic perspective, thus providing a theoretical basis for wood heat treatment research. In this study, we performed dynamic simulations at atmospheric pressure (0.1 MPa) and pressurized (0.2 MPa, 0.4 MPa, and 0.6 MPa) conditions under a combination of NPT. In addition, five aspects were analyzed in terms of energy change: cell parameters and density, cellulose mean square displacement, number of hydrogen bonds, and mechanical properties. The results showed that pressurized hydrothermal treatment increased the densification of the wood, decreased the volume, and increased the density. As the pressure increased, the difference between the average value of the nonbond energy and the total potential energy gradually decreased, the bond energy decreased, and the interatomic repulsive force within the molecule gradually weakened. The increase in the number of hydrogen bonds enhanced the restraining effect on the arrangement of cellulose molecular chains and slowed down the movement of the cellulose chains. Young’s modulus (E) and shear modulus (G) increased with increasing pressure, and Poisson’s ratio (γ) and K/G decreased with increasing pressure during the pressurized hydrothermal treatment of wood. The pressurized hydrothermal treatment increased the stiffness and decreased the toughness of the wood compared with those of the model with atmospheric pressure hydrothermal treatment.

Optimizing Scale for Decentralized Wastewater Treatment: A Tool to Address Failing Wastewater Infrastructure in the United States

Wastewater systems (sewered or on-site septic tanks) are failing across the U.S. Economically disadvantaged populations, communities of color, tribal lands, and rural/peri-urban areas are especially vulnerable. Efficient deployment of public and private capital to assure appropriate service levels and affordability is a critical need. We present a modeling framework to identify economically optimal wastewater network layout and component sizes. Six system configurations are considered, which include gravity versus pressurized collection system flow and treatment of septic effluent versus raw wastewater. A case study for Uniontown, Alabama─a community that has been in national news for the failure of their wastewater infrastructure─is presented. We find that a decentralized network that separates and stores solids on-site, prior to conveyance to a cluster-scale treatment site, has a fraction of the capital and operating cost of a centralized system that is currently proposed. Broader implications are discussed.

Effects of Pressurized Superheated Steam Treatment on Dimensional Stability and Its Mechanisms in Surface-Compressed Wood

Shape stability is one of the most important properties of surface-compressed wood used as a substitute for other energy-intensive adhesives, concrete, and metals. This study evaluated the dimensional stability, surface wettability, chemical structure, cellulose crystalline structure, and microstructure of surface-compressed wood. The surface-compressed wood was then treated with pressurized superheated steam. The equilibrium moisture content, thickness swelling ratio, and wettability of the wood decreased by 20.39%, 30.63% (moisture absorption), 40.51% (water absorption), and 86.95% after pressurized superheated steam treatment, respectively. In the pressurized steam environment, hemicelluloses were significantly degraded, significantly reducing the strong hygroscopic groups, particularly hydroxyl groups. The crystallinity and crystal width of cellulose in the compressed wood also increased by 8.02% and 37.61%, respectively, after pressurized superheated steam treatment, corresponding to dimensional stability. Dimensional stability, namely the shape fixation of the surface-compressed wood, is a complex mechanism, including the hydrophobization of cell walls, the formation of cross-linkages, the reformation of microfibril chains, microstructural changes, and the relaxation of inner stresses, which reduced or even eliminated the recovery. This study demonstrates that pressurized steam treatment can effectively enhance dimensional stability in surface-compressed wood, which contributes to the substantial use of surface-compressed wood in the building and construction industries. We will further explore the relationship and mechanism between superheated steam pressure, treatment time, and dimensional stability.

Mechanical properties of surface-compressed wood resulting from the compression ratio and density distribution

Surface-compressed wood, with controllable mechanical properties according to the production process, could be utilized in timber products as a substitute for energy-intensive adhesives, concrete, and metals. The surface compression of wood was carried out in an open hot-pressing system at 180 °C with a compressed thickness of 2 to 18 mm. The surface-compressed wood was treated by atmospheric heat treatment or 0.30 MPa pressurized superheated-steam heat treatment at 180 °C for 2 h. This study investigated the mechanical properties of surface-compressed wood, namely, its bending, compression, and hardness properties. The results showed that the maximum density and average density of the compressed layer surpassed 1.10 g/cm3 and 0.80 g/cm3 when the compression ratio was 33%. Moreover, the surface-compressed wood with a sandwich density structure had properties that were comparable to, or even surpassed, raw wood, traditional compressed wood, and some engineered timber products. The specific strength (179 to 203 × 103 m2/s2) of surface-compressed wood was slightly higher than other wood-based materials (65 to 197 × 103 m2/s2). And the contribution of sandwich structure to MOR and MOE increase was positively correlated with wood surface density. The results obtained from this study could help engineers utilize more fast-growing wood and develop new products and wood connectors. This work may contribute toward the substantial use of surface-compressed wood in the building and construction industries with great benefits to the environment.

Effect of nano-silica coating combined with pressurized Ar treatment on postharvest quality and reactive oxygen species metabolism in sweet cherry fruit

The mechanisms of effect of nano-silica coating and pressurized Ar on regulating reactive oxygen species (ROS) generation and scavenging in the senescence of sweet cherries remains unclear. The amounts of reactive oxygen species, hydrogen peroxide, non-enzymatic antioxidants and antioxidases, and cell membrane lipid peroxidation in sweet cherries were determined. Nano-silica coating, pressurized Ar, and the combination of these two treatments, all significantly delayed senescence by suppressing decay rate, and maintained good sensory quality. In additional, all treatments inhibited the generation and accumulation of superoxide anion and hydrogen peroxide, and mitigated the lipid peroxidation of cell membranes of sweet cherries. The combination of these two treatments maintained higher contents of ascorbic acid and glutathione, and enhanced the activities of antioxidases in sweet cherries. It is suggested that nano-silica coating and pressure Ar mediated the ROS metabolism, which might have a role in retaining the quality sweet cherries during cold storage.

Extraction, separation, and utilization of components contained in waste bamboo by pressurized microwave-assisted ethanol solvent treatment

Extraction, separation, and utilization of components contained in waste bamboo by pressurized microwave-assisted ethanol solvent treatment

Production and antioxidant activity of phenolic compounds from indigo plant waste using pressurized microwave-assisted hydrothermal treatment followed by water extraction

Production and antioxidant activity of phenolic compounds from indigo plant waste using pressurized microwave-assisted hydrothermal treatment followed by water extraction

Extraction of Pectin from Satsuma Mandarin Orange Peels by Combining Pressurized Carbon Dioxide and Deionized Water: a Green Chemistry Method

Pectic oligosaccharides have vital properties that are dependent on their molecular assemblies, such as the degree of esterification (DE) and branched side chains. The molecular structures are affected by the extraction solvents and conditions. In this study, we used pressurized carbon dioxide treatment (CT) as a novel method for pectin extraction from fresh and ripe orange peels and compared the total yield, DE, molecular weight, and monosaccharide compositions of the product obtained with those of products obtained using conventional extraction methods, such as heating with HCl or chelating with sodium hexametaphosphate (SHMP). CT provided a yield of approximately 3.8%, which was less than that of HCl (9.9%/dry weight). However, DE in the CT extract was approximately 94%, which was higher than that of HCl (75%) and SHMP (59%). The molecular weights of pectins in the CT extract appeared to be higher than that of HCl, except at a pressure of 2 MPa. β-Galacturonic acid was the major monosaccharide in pectin extracted by HCl and SHMP, whereas that was decreased in CT extract from fresh oranges. The results showed that extraction with CT contributed to a high DE pectin yield and diverse pectin molecular structures compared to conventional methods, although its application resulted in a lower overall pectin yield. These findings suggest the possibility of manufacturing oligosaccharides with novel properties.

Effects of a pressurized water treatment on internal gelation sol–gel microspheres

Based on previous observations that a pressurized water treatment (PWT) prevented cracking of sol–gel microspheres, we investigated the effects of a PWT on microsphere crystallinity, density, and specific surface area (SSA). Results were used to determine how a PWT alters the properties of microspheres upon drying and heating. Microspheres with diameters near 100–200 µm were prepared with and without a PWT and measured using x-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption (BET), and pycnometry. Properties of air-dried microspheres processed with and without a PWT are compared. In addition, the properties of microspheres processed using a PWT are reported after heating to 150, 450, 750, 1050, and 1350 °C. XRD measurements indicate that the PWT step improves the crystallinity of air-dried microspheres. XRD data were also used to calculate crystallite size, which increases with higher heat-treatment temperatures. TEM images support crystallite size calculations from XRD data and provide an indication of the range of crystallite sizes, particularly for samples processed at higher temperatures where crystallite sizes are too large for estimation using the Scherrer formula. Density and SSA measurements performed as a function of heat-treatment temperature indicate that a PWT increases the density of air-dried microspheres, creates a pore network, and that significant densification occurs between 450 and 750 °C. These results may be used to inform decisions on internal gelation flowsheet parameters to optimize the microsphere formation and gelation step, prevent microsphere cracking, and produce microspheres suitable for subsequent coating operations or pressing into pellets.

Constructing mild expanded graphite microspheres by pressurized oxidation combined microwave treatment for enhanced lithium storage

The modified graphite anode materials have some prominent advantages over other anode materials in the industrial applications. A novel simple and gentle method is proposed to synthesize the mild expanded graphite microspheres (MEGMs) from flake graphite spheres through a combined modified pressurized oxidation combined with the microwave treatment. The microstructural results demonstrate that moderately expanded MEGMs with an expansion volume between 4 and 10 ml·g−1 exhibit a highly microporous structure with an enlarged interlayer spacing, a decreased microcrystalline size, as well as an increased number of functional groups on the surface, resulting in the increased storage sites and spaces for lithium ions and the enhanced diffusion rate of lithium ions. When used as the anode material for lithium-ion batteries, the MEGM-T75t30 obtained by oxidation treatment at 75 °C for 30 min followed by microwave irradiation for expansion displays a high reversible capacity of 446.7 mAh·g−1 at 100 mA·g−1 after 100 cycles and excellent rate performance (330 and 116 mAh·g−1 at 800 and 3200 mA·g−1, respectively). Therefore, the MEGMs prepared by this convenient and mild method show excellent electrochemical properties and good application potential.

Valorization of canola by-products: Concomitance of flavor-active bitter phenolics using pressurized heat treatments

Canola by-products have considerable potential as functional ingredients and antioxidants due to the presence of unique phenolic compounds. Thus, extraction of flavor-active phenolics present in canola by-products is important for their co-production and valorization. The quantity and quality of these unique phenolic compounds could affect the sensory and organoleptic properties of any product or ingredients derived post-processing of the canola by-products. This study evaluated, both quantitatively and qualitatively, the formation of these flavor-active compounds under pressurized temperature processing. Particle size, extraction temperature, type of solvent extractants (70%v/v methanol or ethanol), were factors examined for extracting the major flavor-active phenolic compounds including thomasidioic acid (TA), kaempferol 3-O-β-sophoroside (KS), kaempferol 3-O-(2‴-O-sinapoyl-β-sophoroside) (KSS). Two other kaempferol derivatives, kaempferol 3-(2″-hydroxypropionylglucoside)-4′-glucoside (K-4-G) and kaempferol 3-[2″-glucosyl-6″-acetyl-galactoside] 7-glucoside (K-7-G) were also tentatively identified in the extract. The results confirmed that extraction temperature and solvent type had a significant impact (p < 0.05) on the extraction of flavor-active compounds TA and KS. Thus, all parameters had a signifcant impact (p < 0.05) on the extractability of KSS. Particle size and concentration had a significant impact on extraction of K-7-G where as all other parameters excluding particle size had a significant impact (p < 0.05) on the extraction of K-4-G.

Evaluation of Pressurized Inert Gas Treatments on the Postharvest Quality of Blueberries

This study investigated the efficacy and mechanism of pressurized inert gas treatment for the quality preservation and shelf life extension of fresh blueberries. The change of physiological metabolisms and surface microbial attributes of pressurized gas-treated blueberries during 4 °C storage were measured over a 12-day period. Compared with the control group (without treatment), the pressurized inert gas treatments with argon, carbon dioxide, and nitrogen could effectively suppress the rate of respiration and ethylene production, reduce the water loss, and avoid softening and anthocyanin degradation in the blueberries. Meanwhile, the surface color, citric acid content, and soluble solid content in the blueberries were well maintained during the storage. Pressurized inert gas-treated blueberries carried significantly (P < 0.05) less microbial populations (yeast, mold, and bacteria) than those without the treatments. The findings from this study indicated that pressurized inert gas treatment could effectively preserve the quality and potentially be applied for the shelf life extension of fresh blueberries.

Extraction of phenolic compounds from Chlorella sp. microalgae using pressurized hot water: kinetics study

Chlorella sp. are among the highest cultivated species of microalgae. They are considered as an important functional food due to their abundance and valuable health benefits. It would be useful to develop an effective method for phenolic compound extraction from Chlorella sp. using safe technology and green solvents for the applications in food and pharmaceutical fields. Pressurized hot water extraction (PHWE) is an alternative for this purpose. PHWE was employed to extract phenolic compounds from Chlorella sp. microalgae at temperatures between 100 and 250 °C. The data collected is used to create the kinetics of the extraction process. The kinetics studies revealed that the extraction from Chlorella sp. microalgae using pressurized hot water treatment follows first-order kinetics and is strongly dependent on temperature. An increasing trend in the calculated values of mass transfer coefficient, k, was noticed, with increasing temperature. The activation energy, Ea, was calculated as 11.146 kJ/mol for the extraction treatment.

Fresh-cut orange preservation based on nano-zinc oxide combined with pressurized argon treatment

The effects of pressurized argon (Ar) and nano zinc oxide (ZnO) coating treatment on the quality properties of fresh-cut orange were explored. The changes of various quality parameters including physical-chemical indicators (total soluble solid, pH, titratable acid, ascorbic acid, mass loss, color and volatile characteristic odor), sensory evaluation and microbial (total aerobic bacteria and fungi) analysis during storage were investigated. Compared with other treatments and controls, combined treatment of nano zinc oxide coating (0.7 g/L) and pressurized argon (2 MPa, 30 min) effectively reduced mass loss and the increase in soluble solids and the reduction of titratable acid and ascorbic acid contents, and effectively inhibited the growth of total aerobic bacteria and fungi. In addition, through electronic nose detection, the combined slices had the least volatile characteristic odor, which were mainly aldehydes, alcohols, esters and terpenes in the later storage period. In summary, the combination of pressurized argon and nano zinc oxide coating was a promising method for fresh-cut fruit preservation. • Pressurized argon combined with nano zinc oxide treatment decreased water mobility. • Pressurized argon combined with nano zinc oxide treatment reduced flavor odor. • Pressurized argon combined with nano zinc oxide treatment inhibited bacteria and fungi growth. • Pressurized argon combined with nano zinc oxide treatment extended shelf life of fresh-cut orange.