Superheated Steam Treatment Research Articles

Effect of superheated steam treatment on the lipid stability of whole wheat flour

This study aimed to investigate the effect of superheated steam treatment (SST) on lipid stability of whole wheat flour (WWF) during storage. After SST, the lipase and peroxidase of WWF were inactivated, and lipoxygenase activity was lower than 5% of its initial value. The total tocopherols decreased slightly in all SST groups, especially it only decreased by 1.1% at 190 °C for 5 s. Furthermore, the increase of fatty acid value in the control group was over 100-fold than that of the SST groups during storage. The unsaturated fatty acids and total tocopherols in WWF decreased gradually, but the decrease was alleviated by SST at 190 °C for 5 s. After storage, the relative content of hexanal and 2-pentylfuran in the SST groups were 4 and 0.3-fold than those in the control group, respectively. Thus, SST may be a potential approach to stabilise the quality of WWF.

Change in Micromechanical Behavior of Surface Densified Wood Cell Walls in Response to Superheated Steam Treatment

The combination of surface densification and superheated steam treatment is an effective method to improve the mechanical properties and dimensional stability of low-density wood. The objective of the current work is to evaluate the effects of superheated steam treatment on the micromechanical behavior of surface densified wood. The microstructure, chemical composition, cellulose crystalline structure, and micromechanical behavior of surface densified wood under different superheated steam pressures were investigated. Results indicated that both 0.1 MPa and 0.3 MPa superheated steam treatments increased the elastic modulus and hardness of fiber cell walls in surface densified wood. However, the average creep ratio and maximum creep compliance J(50) of surface densified wood under 0.3 MPa decreased by 41.59% and 6.76%, respectively, compared with untreated wood. The improvement of elastic modulus, hardness and creep resistance of surface densified wood treated with superheated steam was associated with the increase of relative crystallinity (CrI) and crystalline size. In addition, 0.3 MPa superheated steam treatment displayed a better effect on the enhancement of the elastic modulus, hardness, and creep resistance of the fiber cell wall than 0.1 MPa superheated steam treatment.

Influence of superheated steam treatment with tempering on lipid oxidation and hydrolysis of highland barley during storage

Highland barley is an excellent source of dietary fiber and therefore this grain is receiving more and more popularity. The aim of this study was to improve the shelf life of highland barley by inactivating lipolytic enzyme using superheated steam (SS) with proper tempering and effects of SS processing on storage properties were compared. Results indicated that barley was stabilized by SS processing (160 °C) holding for 6 min with 6 h of tempering time could effectively reduce 38.85% lipase activity and 100% peroxides (POD) activity. Low-field nuclear magnetic resonance results showed tempering for 6 h provided proper water distribution of kernels meeting enzyme. Under the optimal conditions, highland barley maintained low free fatty acid (FFA) level and peroxide value (PV) after 8 weeks of storage and the storage quality in the form of flour has been improved more significantly than the kernels, lowing FFA levels of kernels by 15.00% and flour by 37.55%, respectively (P < 0.05). The changes of FFA composition was slowed down by SS processing after storage. Furthermore, color values and water hydration properties were altered by SS processing during the storage. In conclusions, these data highlighted the importance of SS processing, especially with proper tempering, and provided valuable information for the industry to improve the storage qualities of highland barley.

Wheat flour superheated steam treatment induced changes in molecular rearrangement and polymerization behavior of gluten

Wheat flour superheated steam treatment can improve the baking food quality by modifying the functionality of wheat flour. To reveal the underlying mechanism of improving wheat flour quality by superheated steam treatment, the gluten molecular rearrangement and polymerization behavior of wheat flour upon superheated steam were studied. Molecular size distributions of samples were analyzed using size exclusion (SE-HPLC) and electrophoresis, which illustrated that superheated steam treatment promoted the aggregation of gluten due to cross-links of disulfide (SS) bonds. Superheated steam treatment increased the SDS-insoluble proteins content from 63.07% (native wheat flour) to 93.32% (treated at 150 °C for 1 min). Infrared spectroscopy (FTIR) was used to calculate the different secondary structures percentages of gluten, suggesting that superheated steam treatment increased intermolecular β-sheet and α-helix while it decreased anti-parallel β-sheet, β-turn and β-sheet. Furthermore, thermo gravimetric analysis (TGA) and rheology suggested that superheated steam treatment enhanced gluten mass but weakened gel system due to molecular rearrangements of SS bonds and hydrogen bonds.

Physicochemical, crystalline characterization and digestibility of wheat starch under superheated steam treatment

This paper explored the impact of superheated steam (SS) treatment on the physicochemical, crystalline characteristics and in vitro digestibility of wheat starch. Upon SS treatment, treated samples showed lower swelling power, solubility, and viscosities, but had higher gelatinization temperature, which might be due to the partial gelatinization of starch granules. This agreed with micromorphology characterization, indicating the degradation of Maltese cross. In addition, SS treatment decreased the long-range crystalline and short-range order of starch, compared to native starch sample. This change of physicochemical and structural properties was responsible for the decrease of starch hydrolysis rate. Meanwhile, SS treatment obviously increased the slowly digestible starch (SDS) and resistant starch (RS) content from 10.6% to 7.9% (native starch) to 17.2% and 13.6% (150 °C, 1 min), respectively. This knowledge indicates that superheat steam technology possibly is a promising strategy in starch modification.

The contribution of superheated steam treatment of wheat flour to the cake quality

The effect of superheated steam treatment on the physicochemical properties of wheat flour and quality characteristics of cake were investigated. Superheated steam treatment significantly increased the swelling power, viscosities and gelatinization temperature, but reduced the gelatinization enthalpy (p < 0.05), compared with native wheat flour. However, the dough made from the treated flour was harder to form. Moreover, superheated steam treatment significantly increased the value of falling number. Cake quality was affected by the changes in the physicochemical properties of wheat flour. Results showed that superheated steam treatment significantly decreased the hardness of cake from 1465 g (native flour) to 377 g (150 °C, 1 min), and increased the specific volume of cake from 3.12 mL/g (native flour) to 3.9 mL/g (150 °C, 1 min). The present study suggests that superheated steam treatment has great potential as a flour modification technology for cake quality improvement.

Effects of superheated steam treatment of wheat on physicochemical properties of wheat flour and cracker quality

In order to study the effects of superheated steam (SS) treatment of wheat on the physicochemical properties of wheat flour and cracker quality, soft wheat was treated with SS and the pasting properties and solvent retention capacity (SRC) of wheat flour and cracker quality were determined. The results showed that both the physicochemical properties of wheat flour and cracker quality were significantly affected by SS treatment of wheat. Pasting properties of wheat flour were affected by SS treatment of wheat significantly, which indicated the increase of gelatinized starch and damaged starch. At the steam temperatures from 140 to 215 °C, 50% sucrose SRC (SuSRC), 5% sodium carbonate SRC (SCSRC), and water SRC (WSRC) increased with the extending of treatment time. Meanwhile, 5% lactic acid SRC (LASRC) and gluten performance index (GPI) initially increased and then decreased. Besides, the spread ratio, hardness and fracturability of crackers were improved. According to the results above, we concluded that SS treatment of wheat had significant effects on the physicochemical properties of wheat flour and could improve cracker quality in a relatively short time (shorter than 3 min). The most suitable condition for improving cracker quality was SS treatment of wheat at 165 °C for 3 min.

Static Mechanical, Thermal Stability, and Interfacial Properties of Superheated Steam Treated Oil Palm Biomass Reinforced Polypropylene Biocomposite

In this study, three types of oil palm biomass (OPB) namely, oil palm mesocarp fiber (OPMF), oil palm empty fruit bunch (OPEFB) and oil palm frond (OPF), were studied and compared as the alternative fillers in the biocomposite reinforced polypropylene (PP). The fibers were treated using the optimal condition of superheated steam treatment obtained from previous study. The OPB/PP biocomposites at weight ratio of 30:70 were fabricated by melt blending technique and hot pressed moulding. Results showed that the tensile and flexural properties of optimized-SHS-treated OPB/PP biocomposites were improved by 9 – 30% and 9 – 12%, respectively compared to the untreated OPB/PP biocomposites. The same observation was recorded for thermal stability. Improved surface morphology as shown by the tensile fracture surface indicates better interfacial adhesion between SHS-treated OPB fibers with PP matrix during blending. Overall results showed that OPF/ PP biocomposites had better properties compared to biocomposites prepared from OPMF and OPEFB, suggesting that OPF is a better OPB fiber choice as a filler in PP reinforced biocomposite.

Superheated steam processing improved the qualities of noodles by retarding the deterioration of buckwheat grains during storage

Buckwheat freshness plays a key role in the qualities of noodles. The present study focuses on the protective effects of superheated steam (SS) processing on the quality deterioration of noodles made from stored buckwheat grains. Changes of the volatile compounds, lipid degrading enzymes, pasting properties, farinograph characteristics of buckwheat grains, together with the cooking qualities and texture profiles of buckwheat noodles were investigated. Results suggested that 3-methyl-butyraldehyde and hexanal were the markers of lipid oxidation and flavor change of buckwheat grains during storage. SS treatment inactivated lipase, lipoxygenase and peroxidase and affected the generation of off-flavor volatile compounds of buckwheat grains, thus retarded the flavor deterioration of buckwheat noodles made from stored buckwheat. Storage significantly (P < 0.05) decreased the pasting viscosities, water absorption and development time of buckwheat dough. SS treatment maintained the pasting properties of starch stable and enhanced the elasticity and strength of the dough, leading to the improvement of cooking qualities and texture profiles of buckwheat noodles. Therefore, SS processing was an effective way to improve the qualities of buckwheat noodles by stabilizing buckwheat grains.

Sandwich compression of wood: effect of superheated steam treatment on sandwich compression fixation and its mechanisms

The permanent fixation is essential for the full industrialization of sandwich-compressed wood. In this study, sandwich-compressed wood was modified with superheated steam for compression fixation. Effects of superheated steam pressure on set-recovery were investigated. Changes in microstructure, chemical structure and cellulose crystalline structure of the compressed wood were analyzed, to clarify the reason and mechanism for sandwich compression fixation under superheated steam treatment. It was found that set-recovery of central-compressed wood was higher than that of surface-compressed wood. Effects of superheated steam treatment on set-recovery were statistically significant (P < 0.05). Higher superheated steam pressure contributed to lower set-recovery, but the extent of the impact of superheated steam pressure depended on the pressure levels and the reasons causing the set-recovery (exposure to high humidity, immersion in water or boiling in water). The decreased set-recovery was related to micro-cracks in the cell wall, degradation of hemicelluloses, loss of the C=O linked to the aromatic skeleton in lignin and increase in crystallinity. This research demonstrated that superheated steam treatment is effective in permanently fixing the compression of sandwich-compressed wood.

Effect of superheated steam treatment on the structural and digestible properties of wheat flour

The structural and digestive properties of wheat flour which had been treated with superheated steam were investigated. Superheated steam treatment increased the degree of gelatinization (DG) and water absorption indexes (WAI) while decreased water solubility indexes (WSI) of wheat flour samples, compared with native wheat flour. The structural properties of wheat flour were characterized using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), particle size analyzer, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The starch granules agglomeration and denatured gluten proteins aggregation of samples were observed after treated with superheated steam. Additionally, Superheated steam treatment decreased the relative crystallinity and short-range order structure of starch. These structural changes were related to the starch digestibility. Superheated steam treatment caused the significant increase for slowly digestible starch (SDS) contents from 21.5% of native wheat flour to 35.0% of treated wheat flour (170 °C, 4 min). Additionally, the equilibrium hydrolysis concentration (C∞) and the kinetic coefficient (k) of treated wheat flour were lower than native wheat flour, indicating that superheated steam treatment decelerated the hydrolysis rate. These results contributed to the applications of superheated steam technology in wheat flour modification.

Effect of superheated steam treatment on yield, physicochemical properties and volatile profiles of perilla seed oil

This study investigated the effect of superheated steam (SHS) treatment on the yield and quality properties, including volatile compounds of perilla seeds oil (PO). SHS treatment resulted in ruptured seed coat and damaged cellular structure, increasing oil yield (78.81 g/100 g seeds), about 2.5-times higher yield than the untreated seeds (33.11 g/100 g seeds). The viscosity (~89 mPa s), color parameters (L*a*b*), acid value (0.19 mg KOH/g), and peroxide value (1.02 meq/kg) of SHS-treated POs were similar with that of the untreated PO, indicating no oil rancidity by SHS treatment. SHS-treated PO showed a dramatic reduction of lipase activity from 37.44 to 0.80 μmol/g, 3-times higher phenolic content and 5-times higher antioxidant activity than that of the untreated PO. The major volatiles were 2,4-heptadienal, 4-methyl-5-(2-methyl-2-propenyl-2(5H)-furanone, 3-(4-methyl-3-pentenyl)furan perillen, and 3-methylpentane in POs. The normalized relative intensities of the volatiles were reduced for SHS-treated PO. Thus, SHS could be an effective treatment for high oil yield without originating odor characteristics compounds in PO.

Nutritional values of Baccaurea pubera and comparative evaluation of SHS treatment on its antioxidant properties.

Baccaurea pubera is a blood red coloured fruit found exclusively in Borneo. This study was conducted to evaluate the effect of superheated steam treatment on its antioxidant properties and mineral content as well as to determine nutritional values of the fruit. The fruits were treated with superheated steam at 170°C for 15min prior to extraction and freeze drying. The results showed that, in comparison to the control, superheated steam treatment enhanced the total phenolic content by 147.8% (287.16mg GAE/100g vs. 115.87mg GAE/100g) and DPPH radical scavenging activity by 23.7% (66.94% vs. 54.13%). However, there were reductions, as compared to the control treatments, in total flavonoid content by 16.5% (8.29mg QE/100g vs. 9.93mg QE/100g), lycopene content by 28.6% (0.020μg/100g vs. 0.028μg/100g) and ferric reducing antioxidant power by 22.2% (844.41mg TE/100g vs. 1085.15mg TE/100g). The superheated steam treatment was also observed to reduce the mineral content of the fruit, from as little as 3.6% to as high as 52% depending upon the specific mineral.

Effect of thermal processing for rutin preservation on the properties of phenolics & starch in Tartary buckwheat achenes

The endogenous rutin-degrading enzymes (RDEs) in Tartary buckwheat (TB) considerably limit the development of TB functional foods. In this study, three thermal treatments, including superheated steam (SS), saturated steam (ST), and far-infrared drying (FID), were used to inactivate RDEs in TB. Results showed that SS and ST could efficiently inactivate RDEs, whereas FID could not. The extractable rutin contents in TB were increased by 52.3% and 12.3% by SS and ST, respectively, with 90 s of treatment time. Furthermore, the properties of phenolics and starch were used to evaluate the influence of thermal inactivation on TB. Results showed that the soluble phenolic compounds contents in TB were significantly improved (p < 0.05) by SS. The bound phenolic compounds contents were decreased after SS and ST treatments. The change in antioxidant properties was consistent with that of phenolics and flavonoids. Besides, the starch in SS- and ST-treated TB achenes had higher relative crystallinity, setback, transition temperatures, rapidly digestible starch, and slowly digestible starch contents, but a lower ratio of 1047 cm−1/1022 cm−1, peak viscosity, breakdown, gelatinization enthalpy, and resistant starch contents, than native TB starch. In conclusion, SS was a better method for the inactivation of RDEs than ST.

Improvement of cake quality by superheated steam treatment of wheat

In order to improve cake quality, soft wheat was treated with superheated steam (SS) and used to make Madeira cakes, after which the cake batter properties and cake quality were analyzed. Both the cake batter properties and cake quality were significantly affected by SS treatment and cake quality was improved at some specific conditions. Batter viscosity was higher than the control at most conditions of SS treatment and it increased when treatment time was increased from 1 min to 7 min at 140 °C, 165 °C, 190 oC and 215 °C. Batter density decreased at some specific conditions. Except the treatment of wheat at 115 °C for 1 min and at 140 °C for 5 min and 7 min, other conditions all led to the decrease of baking loss of cakes. Specific volume of cakes increased at the conditions of 165 °C for 3 min, 190 °C for 1min and 215 °C for 1min. Texture properties and sensory qualities were improved at relatively high temperature for a short time of SS treatment. In conclusion, SS treatment of wheat at the conditions of relatively high temperature for a short time could improve cake quality significantly and SS treatment at 190 °C for 1 min was the best condition.

Modification of cellulose degree of polymerization by superheated steam treatment for versatile properties of cellulose nanofibril film

Cellulose from oil palm empty fruit bunch (OPEFB) was subjected to superheated steam (SHS) treatment at 150 °C for 1 and 2 h to produce cellulose with different degree of polymerization (DP). The treated OPEFB cellulose was subjected to a wet disc milling process to produce cellulose nanofibrils (CNFs), followed by nanocellulose film production using casting-evaporation technique. Reduction of DP by 23 and 40% were recorded after SHS treatment of OPEFB cellulose for 1 h (SHS1) and 2 h (SHS2), respectively, as compared to the untreated OPEFB cellulose. CNFs produced from treated cellulose (CNF-SHS1 and CNF-SHS2) exhibited smaller diameter and were less entangled compared to CNF from untreated cellulose (CNF-UT). These contributed to smoother CNF-SHS films. The highest light transmittance was recorded for CNF-SHS2 film, followed by CNF-SHS1 and CNF-UT films. The increment in transmittance value is in accordance with the reduction in cellulose DP. Lower DP also caused CNF-SHS films to have less wetting property as a result of smoother film surface. Mechanical properties were affected by DP values suggesting the possibility to control mechanical properties of CNF films in relation to DP. Overall, SHS is an efficient treatment method to reduce cellulose DP with the advantage of controlling CNF film properties towards the production of a versatile CNF film.

Durability of Superheated Steam-Treated Light Red Meranti (Shorea spp.) and Kedondong (Canarium spp.) Wood against White Rot Fungus and Subterranean Termite

In this study, the effect of superheated steam (SHS) treatment on the changes of the chemical composition and biological properties of two tropical hardwoods was investigated. SHS was carried out on light red meranti (Shorea spp.) and kedondong (Canarium spp.) wood with dimensions of 410 × 25 × 25 mm, using superheated steam as the heating medium. Wood samples were heat-treated at nine treatment levels, ranging from 172 to 228 °C and 95 to 265 min, respectively. The chemical constituents and resistance against white rot fungus (Pycnoporus sanguineus) and subterranean termite (Coptotermus curvignathus) of the treated wood were evaluated. A significant reduction in holocellulose content and increment in lignin was observed after SHS treatment. Consequently, the resistance against white rot fungus and termites improved. The biological durability improved with an increasing treatment temperature and time. A regression analysis revealed that the reduced equilibrium moisture content imparted superior biological resistance to the treated wood. Weight loss caused by the thermal degradation also served as a good indicator for fungal decay, as the loss of weight was directly proportional to the improvement in fungal resistance. However, this did not apply to termite resistance, as a very weak relationship was found between the two variables.

Effect of superheated steam treatment on quality characteristics of whole wheat flour and storage stability of semi-dried whole wheat noodle

Quality characteristics of whole wheat flour with superheated steam treatment and storage stability of semi-dried whole wheat noodle were investigated, as well as texture and cooking properties of cooking noodles. Superheated steam treatment significantly reduced the total plate count and the activities of lipase, lipoxygenase and polyphenol oxidase in whole wheat flour (p < 0.05), and decreased the free phenolic content. When treated at 155–170 °C, the thermomechanical properties of whole wheat dough improved with the increase of the development time, stability and C2 torque. Superheated steam treatment showed no obviously detrimental effects on hardness and cooking loss of noodle. During storage, treated semi-dried whole wheat noodle exhibited slower rate of microbial growth. Superheated steam treatment significantly reduced the acidity, inhibited the formation of free fatty acid, and decreased the activities of enzyme during storage. This would delay the deterioration and improve the storage stability of semi-dried whole wheat noodle.

Steam‐Induced Coarsening of Single‐Unit‐Cell MFI Zeolite Nanosheets and Its Effect on External Surface Brønsted Acid Catalysis

AbstractCommonly used methods to assess crystallinity, micro‐/mesoporosity, Brønsted acid site density and distribution (in micro‐ vs. mesopores), and catalytic activity suggest nearly invariant structure and function for aluminosilicate zeolite MFI two‐dimensional nanosheets before and after superheated steam treatment. Yet, pronounced reaction rate decrease for benzyl alcohol alkylation with mesitylene, a reaction that cannot take place in the zeolite micropores, is observed. Transmission electron microscopy images reveal pronounced changes in nanosheet thickness, aspect ratio and roughness indicating that nanosheet coarsening and the associated changes in the external (mesoporous) surface structure are responsible for the changes in the external surface catalytic activity. Superheated steam treatment of hierarchical zeolites can be used to alter nanosheet morphology and regulate external surface catalytic activity while preserving micro‐ and mesoporosity, and micropore reaction rates.

Tensile properties of recycled carbon fibers subjected to superheated steam treatment under various conditions

A new treatment condition involving superheated steam (SHS) was proposed to achieve optimal carbon fiber recovery with a minimal decrease in fiber strength. Unidirectional carbon fiber reinforced sheets were exposed to SHS at 650 °C for 1 h with the addition of N2 or CO2 as process gas. The recovery was assessed based on mass change and using thermogravimetry and differential scanning calorimetry. The results showed that the addition of N2 efficiently suppressed the decrease in fiber strength and achieved optimal recovery. Weibull parameters indicated that lower strength fibers tended to present a narrower strength distribution. The observation of fracture surfaces and oblique sections indicated that the presence of intrinsic defects and corrosion of surface crystallites under the oxidative condition are responsible for the deterioration of and the changes in the distribution of strength.