Superheated Steam Treatment Research Articles

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.

The microbiome modulating potential of superheated steam (SHS) treatment of dietary fibres

In this study, wheat and oat bran fibres were used to investigate the potential beneficial prebiotic-enhancing effects of superheated steam (SHS) treatment. Following SHS treatment of fibres, in-vitro simulated gastric and intestinal digestion followed by batch culture fermentation was performed. 16S rRNA gene sequencing and short chain fatty acid analysis were conducted, which demonstrated that SHS treatment was associated with significant differences in beta diversity and the relative abundances of several microbial taxa. Principal Coordinate Analysis (PCoA) revealed significant separation between SHS-treated oat and non-treated oat (p = 0.013), and between SHS-treated wheat and non-treated wheat following in vitro batch fermentation (p = 0.042). Abundances of Ruminococcus were found to be significantly higher by 1.09-log in SHS-treated oat when compared with non-treated oat while abundances of Escherichia_Shigella, and Alistipes were significantly lower by 1.47-log and 0.39-log, respectively in the SHS-treated oat samples than the non-treated oat samples (p = 6.85E-06, p = 0.002037, p = 0.002458; respectively). These data demonstrate that SHS treatment of dietary fibre enhanced its effectiveness to modulate the gut microbiome.Industrial Relevance: Superheated steam (SHS) treatment has emerged as an effective method to improve the shelf-life of grains by reducing lipid hydrolysis and oxidation. Our results revealed that SHS treatment of wheat and oat brans led to increased physiological and chemical properties including higher water-binding capacity, water-extractable arabinoxylan, and total phenolics as well as improvement in human gut microbiota. Our results suggest that this method could be implemented in the food industry in order to improve beneficial properties of oat and wheat brans.

Superheated steam effectively inactivates diverse microbial targets despite mediating effects from food matrices in bench-scale assessments

Sanitation in dry food processing environments is challenging due to the exclusion of water. Superheated steam (SHS) is a novel sanitation technique that utilizes high temperature steam to inactivate microorganisms. The high sensible heat of SHS prevents condensation on surfaces. Here we evaluated SHS thermal inactivation of various vegetative and spore forming bacteria and fungi and determined the effect of food matrix composition on SHS efficacy. Capillary tubes with vegetative cells (Salmonella, E. coli O157:H7, Listeria monocytogenes, or Enterococcus faecium), Aspergillus fischeri ascospores, or B. cereus spores (100 μL) were SHS treated at 135 ± 1 °C for 1 or 2 s. After 1 s, SHS achieved a reduction of 10.91 ± 0.63 log10 CFU/mL for vegetative cells, 2.09 ± 0.58 log10 ascospores/mL for A. fischeri, and 0.21 ± 0.10 log10 spores/mL for B. cereus. SHS treatment achieved significant reductions in vegetative cells and fungal ascospores (p < 0.05), however B. cereus spores were not significantly reduced after 2 s and were determined to be the most resistant of the cell types evaluated. Consequently, peanut butter compositions (peanut powder, oil, and water) and milk powder (whole and nonfat) inoculated with B. cereus spores on aluminum foil coupons (2 × 3 × 0.5 cm) were tested. The D161°C values for B. cereus spores ranged from 46.53 ± 4.48 s (6 % fat, 55 % moisture, aw: 0.927) to 79.21 ± 14.87 s (43 % fat, 10 % moisture, aw: 0.771) for various peanut butter compositions. Whole milk powder had higher D161°C (34.38 ± 20.90 s) than nonfat milk powder (24.73 ± 6.78 s). SHS (135 ± 1 °C) rapidly (1 s) inactivated most common vegetative bacterial cells; however B. cereus spores were more heat resistant. B. cereus spore inactivation was significantly affected by product composition (p < 0.05). Compared to the log-linear model (R2 0.81–0.97), the Weibull model had better fit (R2 0.94–0.99). Finally, the ease of peanut butter removal from surfaces increased while the ease of non-fat dry milk removal decreased with the increasing SHS treatment duration. However, allergen residues were detectable on surfaces regardless of SHS treatment. The findings from this study can inform the development of pilot-scale research on SHS.

Manufacturing and compatibilization of binary blends of superheated steam treated jute and poly (lactic acid) biocomposites by melt-blending technique

This work investigated the effect of superheated steam (SHS) jute fiber and poly (lactic acid) (PLA) having a weight proportion of 30:70 which were synthesized using the melt blending method. The goal of this treatment was to boost up the fiber-polymer interfacial linkage. The action was conducted in a superheated steam oven at various times (30–120 min) and temperatures (170–220 °C). The biocomposites were assessed in terms of mechanical characteristics, dimensional stability and morphological properties. Compared to different treatment temperatures, the results showed that treatment at 210 °C for 60 min offered the best tensile characteristics. Because of the presence of SHS-Jute, the tensile, impact, bending and dimensional stability of the bio-composites have been improved. The FTIR and SEM study revealed progress in the interfacial linkage between SHS-Jute and PLA. This interfacial link improves the bending strength of SHS-Jute-PLA biocomposites by about 15.64%. X-ray diffraction (XRD) investigation also showed an elevation in the crystalline structure with the incorporation of SHS-Jute. The degradation tests of the biocomposite were carried out in deionized water. SHS treatment reduces hemicellulose contents in jute fiber which causes water uptake% reduction is 54% in SHS-Jute-PLA. The SHS-Jute-PLA biocomposite appeared with promising characteristics for utilization as a green and ecological substitute particle board material.

Optimal non-thermal inactivation methods by study of the microbial control effect in laver (Porphya sp.).

Laver (Porphya sp.) containing vitamins and minerals has a high total number of bacteria of 6-7 log CFU/g. Changes in microbial count in dried laver by light pulse, ultrahigh pressure, electron beam, and superheated steam treatment were compared. It was decreased by 1.3-1.7 log using IPL (Intense Pulsed Light) for 30-60s at an irradiation distance of 80mm in dried and wet laver. The key parameters of IPL are energy intensity, processing time and irradiation distance. Light pulse inactivation is based on destruction of microbial DNA structure. Electron beam irradiation at 7 and 10kGy resulted reduction of 1.8-3.2 log CFU/g. Dried laver was treated at 500MPa of ultra-high pressure for 3min, total bacterial number showed no change. Applying superheated steam at 150°C for 10s, about 3.3 log CFU/g sterilized. However, it is difficult to apply due to severe damage to sensory quality such as browning.

Different thermal treatments of highland barley kernel affect its flour physicochemical properties by structural modification of starch and protein

Highland barley (HB) has become popular due to nutritional benefits, and thermal treatment could broaden its application. In this study, superheated steam (SS) as a novel commercially thermal treatment was compared with other traditional heating (steam and roasting). The physiochemical properties of treated HB kernels and subsequent produced flour were investigated. After thermal treatments, gelatinization enthalpy was decreased by 38.39% and the degree of gelatinization was increased by 38.40%. SS at 180 °C (SS-180) induced the highest thermal stability, lowest viscoelasticity gel and delayed the starch retrogradation compared to other treatments. Meanwhile, SS-180 caused lowest short-range order and relative crystallinity of starch along with changes in protein secondary structure. Particularly, SS-180 decreased damaged starch content by 6.44% due to starch granules closely wrapped by glue-like protein, while steam and roasting increased it by 32.92% and 21.40%, respectively. Overall, SS treatment is most effective to improve the physiochemical properties of HB.

Prevents kudzu starch from agglomeration during rapid pasting with hot water by a non-destructive superheated steam treatment

Superheated steam (SST) at different moisture contents (10% ∼ 30%) was used to prevent the agglomeration of kudzu starch during rapid pasting with hot water. Changes in pasting-related properties and multi-scale structures were investigated. At moisture content of 20%, SST dramatically reduced the agglomeration rate from 42.20% to 2.97% without destroying the microstructure of kudzu starch or deteriorating the rheological properties of kudzu starch paste, which was superior to the conventional pre-gelatinization treatment. The agglomeration was prevented mainly by decreasing the swelling power and increasing the pasting temperature of kudzu starch. The slight disruption of multi-scale structures may facilitate faster water absorption by kudzu starch, but it was not the primary prevention mechanism. Moreover, the solubility of kudzu starch was not related to the agglomeration, since it was significantly decreased by SST. Our findings could provide new insights into the rapid pasting of starchy powders or flours with hot water.

Quality improvement of grounded peanut using superheated steam treatment by the inhibition of microorganisms, lipase, and aflatoxin

There are many problems of peanuts, such as lipid instability, high microbial content, and aflatoxin. In this study, effect of superheated steam (SS) treatment on the security quality of grounded peanut (GP) was evaluated. Results indicated that concentrations of total bacteria, mold, and Bacillus spp. were maximum reduced 99.26, 100, and 98.57%, respectively. SS processing led to 70% lipase activity and 90% POD activity reduction at 215°C for 2 min, which induced lower AV and PV after 70 days of storage compared to untreated GP. The moisture content dramatically decreased, but color of GP was not affected significantly. SS processing (215°C) was first to apply on degradation of total aflatoxin and aflatoxin B1. Therefore, SS is a novel and effective way to remove the microorganisms and aflatoxin in GP, as well as inhibiting lipase and peroxidase activities so as to improve the lipid stability. Novelty impact statement Mold could be totally inactivated by SS treatment at 140°C for 4 min or over 160°C for 1 min. Compared to untreated GP, SS processing at 140, 160, 180, and 215°C for 4 min could decrease 24.73, 25.52, 30.57, and 35.25% of AV, respectively. SS processing at 215°C for 1 min reduced 77.6% of AFs and 75.7% of AFB1.

Multi-scale structure, rheological and digestive properties of starch isolated from highland barley kernels subjected to different thermal treatments

Thermal treatment has been used to modify starch properties, but few studies pay attention to the change in highland barley starch (HBS) under the whole kernel treatment. The different effect of superheated steam (SS) on the HBS properties from other traditional thermal treatment is still unclear, not mention to the exactly structural change of HBS. This study explored the different effects of SS, steam and roasting treatments of HB kernel on the multi-scale structure, rheological and digestive properties of HBS. Thermal treatments led to the aggregation of HBS granules, the rough surface, and the absence of Maltese cross, as well as the increase in short-chain length ratio and amylose content. Compared with steam and roasting treatments, SS treatment increased the average molecular weight of HBS at 140 °C while reduced it at 180 °C due to starch interactions and depolymerization effect. Multi-scale structure analysis revealed that SS-180 showed the most significant disruption of HBS crystalline structure, the disorder of short-range structure, the decrease in double helix content and the disruption of lamellar structure. These structural changes of HBS resulted in the enhanced thermal stability, and decreased values of G′ and G″ representing the weaker gel structures. Meanwhile, much more resistant starch was converted from rapid digestible starch and slowly digestible starch in SS-treated HB than other thermal-treated HB. In particularly, the most change in multi-scale structure of HBS caused by SS-180 was responsible for its best thermal stability, weakest gel structures and slowest starch digestive rate.

The conformational rearrangement and microscopic properties of wheat gluten following superheated steam treatment

Superheated steam treatment (SST) can improve cereal-based foodstuff quality by altering the gluten properties. In the current study we investigate the effect of SST on the polymerization behavior, conformational rearrangement and microscopic characteristics of gluten, which contribute to determining the molecular mechanisms of SST that impact the gluten properties. Compared with native wheat gluten, SST was observed to induce an increase in sodium dodecyl sulfate (SDS) insoluble gluten. This indicates that SST promoted the polymerization behavior of gluten via the cross-linking of disulfide (SS) bonds. In addition, hydrogen bonds were observed to develop from the micro-environment variation of tryptophan (Trp) residue in the gluten. This consequently had a synergistic effect on the secondary structure, increasing the proportion of intermolecular β-sheets and α-helices. Furthermore, SST enhanced the molecular surface roughness and weakened the gluten network structure. This study could contribute to insight into the improvement of flour quality following SST.

Effect of superheated steam treated wheat flour on quality characteristics and storage stability of fresh noodles

The objective of this study was to enhance the shelf life of fresh noodles prepared by superheated steam (SS) treated wheat flour, and to elucidate the effect of SS treated wheat flour on the quality and storage stability of fresh noodles. SS treated wheat flour improved the initial quality of fresh noodles. Compared with the untreated group, the total plate count (TPC) of SS treated group decreased from 4.10 to 2.87 log10 CFU/g, the L* value increased from 37.98 to 52.00, and the cooking time was significantly shortened from 150 s to 45 s, and the textural properties decreased. SS treatment also improved the storage stability of fresh noodles, prolonged the shelf life to 2 days. During the whole storage period, the TPC of SS treated group was lower than that of the untreated group, and the acidity was significantly reduced. Likewise, the PPO activity and bulk-phase water content were lower, and the water migration was restricted, which inhibited the browning and surface adhesion phenomenon, delaying the deterioration of cooking and textural properties.

Effect of superheated steam treatment and extrusion on lipid stability of black soybean noodles during storage

This study investigated the effect of superheated steam treatment (SST) and extrusion treatment (ET) on the changes of lipids in black soybean noodles (BSN) during storage. Degradation of lipids and formation of volatile compounds were closely related to the endogenous lipid-degrading enzyme activity. Both SST and ET could effectively inactivate lipase, lipoxygenase and peroxidase activity in black soybeans, and thus in the BSN. The content of polyunsaturated fatty acids decreased by 43.6% in non-heat-treated BSN during 7-week storage, whereas the reduction was only 23.0% and 20.7% in SST-190 °C and ET-130 °C groups, respectively. The degradation of tocopherols and tocotrienols, and formation of volatile compounds in the BSN was greatly inhibited during storage by the two heat processes, and ET seems to be more effective. In conclusion, both SST and ET were able to increase the lipid stability of BSN by inhibit the activity of lipid-degrading enzymes. This study could also provide more knowledge that assists to develop high quality of black soybean food products.

Effects of Superheated Steam Treatment on the Allergenicity and Structure of Chicken Egg Ovomucoid.

The aim of this study was to explore the effects of an emerging and efficient heating technology, superheated steam (SS), on the allergenicity and molecular structure of ovomucoid (OVM). OVM was treated with 120–200 °C of SS for 2 to 10 min. The allergenicity (IgG/IgE binding abilities and cell degranulation assay) and molecular structure (main functional groups and amino acids modification) changes were investigated. The IgG-binding ability of OVM decreased and the releases of β-hex and TNF-γ were inhibited after SS treatment, indicating that the protein allergenicity was reduced. Significant increases in oxidation degree, free SH content and surface hydrophobicity were observed in SS-treated OVM. The protein dimer and trimer appeared after SS treatment. Meanwhile, obvious changes occurred in the primary structure. Specifically, serine can be readily modified by obtaining functional groups from other modification sites during SS treatment. Moreover, the natural OVM structure which showed resistance to trypsin digestion was disrupted, leading to increased protein digestibility. In conclusion, SS-induced OVM aggregation, functional groups and amino acids modifications as well as protein structure alteration led to reduced allergenicity and increased digestibility.

Optimization of superheated steam treatment conditions for wheat aleurone layer flour

Although, wheat aleurone layer flour (WALF) is a good source of nutrients, it has certain disadvantages due relatively high levels of lipids and various of microorganisms and enzymes. Therefore, in the current study, the effect of superheated steam (SS) treatment on stabilization of WALF was investigated. This study aims to explore the effects of SS treatment on the degradation of free fatty acids of WALF under different conditions. The optimal process was obtained by an orthogonal optimization experiment, including optimized SS temperature, material moisture and treatment time. Results showed that the free fatty acids content of WALF significantly were decreased with SS treatment as the increase of treatment temperature, material moisture content and treatment times (p<0.05). Therefore, the optimum treatment conditions were selected during SS treatment. Compared with raw WALF, the activity of enzymes, total number of microbial colonies and phytate content in WALF were notably reduced after the SS of optimal condition. Nevertheless, its total dietary fiber content, insoluble dietary fiber content, pentosan content, total phenol content and total antioxidant capacity presented a remarkable increase (p<0.05).

A comparison study of three heating assisted enzyme inactivation pretreatments on the physicochemical properties and edible quality of highland barley grain and flour

Enzyme inactivation is vital to improve the shelf life of highland barley (HB), but the impacts of different heating assisted enzyme inactivation pretreatment (HAEIP) on structure, physicochemical properties and edible quality remain unclear. This study evaluated the effects of three representative HAEIP for microwave, roasting and superheated steam (SS) on the properties of HB grain and flour based on the 50% or 60% inactivation rates for lipase and complete inactivation for peroxidase. Results showed that microwave and SS treatments had the highest and lowest cracking ratio respectively. For the HB edible qualities, the shorter cooking times were observed in R-60 (26 ± 0.84), SS-50 (27 ± 0.09) and SS-60 (27 ± 0.07) groups. Meanwhile, the hardness and chewiness of roasted HB were significantly higher than that in microwaves and SS groups. The HB flour properties varied with different HAEIP. Although all pretreatments showed a substantial reduction in the flour viscosities with treatments intensity increased, the PV values in the two SS groups were the highest. The microwave treatment had the biggest impact on the relative crystallinity and gelatinization degree, while SS pretreatment had the best performance and could be an effective, practical enzyme inactivation methods and enhance HB product quality.

Effects of superheated steam processing on the physicochemical properties of sea rice bran.

Sea rice bran powder is a new type of instant food additive. Currently, its solubility is low, and its flavor is not pleasant. Superheated steam cooking is a promising treatment in cellulose-rich substances, which essentially improves quality. To gain better sea rice bran powder, physicochemical properties of sea rice bran were investigated using 100 °C, 110 °C, 120 °C, and 130 °C superheated steam treatments for 10, 20, 30, and 40 min. After the treatment, these samples were cooled down, dried, and milled to assess sea rice bran powder's product qualities. Profiles of odor, taste, aroma, and aliphatic acids were determined using e-nose, e-tongue, and gas chromatography-mass spectroscopy. Results revealed that superheated steam brought new profiles of odors and tastes for consumers. Superheated steam treatment was found to decrease swelling capacity. Methane (2,2,4,6,6-pentamethyl, heptane) was seen as a significant odor component, whereas umami and bitterness were considered considerable taste components. Superheated steam treatment retained higher content of aliphatic acids: saturated fatty acids 218-204 mg/100 g and unsaturated fatty acids 830-781 mg/100 g. This study discovered that superheated steam is suitable for processing rice bran as food ingredients; 100 °C-120 °C and 10-30 min could be suggested for suitable cooking sea rice bran.

Preparation and characterization of rice starch citrates by superheated steam: A new strategy of producing resistant starch

In this study, starch citrates were synthesized by superheated steam (SS) treatment without changing the granule structure of starch. The degree of substitution (DS) of starch citrates prepared in present study was ranged from 0.015 to 0.064. Fourier transform infrared spectroscopy confirmed that citric acid (CA) and starch were successfully esterified with an absorption peak appeared at 1735 cm−1. In vitro digestion results revealed that the content of resistant starch (RS) was significantly increased by citric acid esterification, which was attributed to the cross-linked structure of starch and the inhibition of gelatinization and swelling. According to the physicochemical properties analysis, the pasting temperature of rice starch citrates were significantly increased by citric acid treatment, while the swelling power and gelatinization enthalpy were significantly decreased and the short- and long-range molecular order of the starch was disrupted after the esterification reaction. These results indicated that it is a feasible method to synthesize starch citrate by superheated steam to increase resistant starch, and it could be used as an alternative approach for preparing starch citrate to conventional hot air treatment.

Sensory Quality Evaluation of Superheated Steam-Treated Chicken Leg and Breast Meats with a Combination of Marination and Hot Smoking.

As the sensory qualities of meat processed using methods such as superheated steam, marination, and hot smoking have not been examined, this study analyzed the sensory quality of chicken meats (leg, breast) and its chemical correlation by determining optimal processing conditions (superheated steam treatment, marination, and hot smoking). Chicken meats were defrosted using room temperature, running tap water, or high-frequency defroster. Marinated meats with herbal extract solution were treated with superheated steam and then hot smoked with wood sawdust; sensory evaluations were performed at each processing step. The products were analyzed for fatty acids and nutrients, along with storage tests under different conditions. High-frequency defrosting showed the lowest drip loss and thawing time compared to other methods. Bay leaves and oak wood were selected as the best sub-materials for higher sensory scores. Optimal superheated steam conditions showed higher overall acceptance (8.86, 8.71) and were set as follows; leg meat (225 °C; 12 min 20 s), breast meat (223 °C; 8 min 40 s). The final meat products possessed good nutritional composition and no severe sensory spoilages were detected during storage despite microbial and chemical degradations. Thus, regular sensory evaluations at each processing step and storage condition were effective for developing superior chicken meat products.

Impact of superheated steam on the moisture transfer, structural characteristics and rheological properties of wheat starch

Superheated steam treatment (SST) can improve cereal-based foodstuff quality. Starch is the major component of cereal-based foodstuffs, playing a key role in food quality. For understanding the effect of SST on the moisture distribution, lamellar structure and molecular weight of wheat starch, the low-field nuclear magnetic resonance (LF-NMR), small angle X-ray scattering (SAXS) and size exclusion chromatography were employed. Compared with native starch, SST reduced the average thickness of crystalline layer and induced the depolymerization of starch molecules, which were attributed to the limited moisture transfer resulting in the partial gelatinization of starch granules. The structural variations had a synergistic effect on the rheological properties of starch samples. Upon SST, treated samples exhibited a weaker pseudoplasticity behavior and increased the deformability and mobility of gels systems. Furthermore, the lower tanδ values of treated starch samples were observed, indicating that the gels systems tended to the solid-like behaviors.

Comparison of six modification methods on the chemical composition, functional properties and antioxidant capacity of wheat bran

The effects of six modification methods (microwaving, steam, extrusion, superheated steam, fermentation and enzymatic treatments) on the chemical composition, processing quality characteristics and antioxidant capacity of wheat bran were determined. Compared with unmodified control bran, all six modification methods had a significant impact on the physical and chemical properties and antioxidant capacity. Microwaving, steam, extrusion, superheated steam and enzymatic treatments could significantly increase the content of folic acid, but decreased the content of vitamin B2. Fermentation increased the proportion of soluble dietary fiber and changed the ratio of insoluble/soluble dietary fiber from 13.65:1 to 8.74:1. The content of water extractable arabinoxylan after microwaving, extrusion and fermentation increased by 12.3%, 33.6% and 46.4%, respectively. Extrusion increased the swelling force of the bran. All modifications increased the total phenolic and ferulic acid contents and the bound ferulic acid content was highest after the steam and extrusion treatments. Enzymatic treatment reduced the DPPH radical scavenging capacity by 16.9%, microwaving increased the ABTS radical scavenging capacity by 12.53% and extrusion increased the ORAC(oxygen radical absorbance capacity) by 4.15%. Overall, extrusion resulted in the greatest improvements in the nutritional and processing qualities of bran, and the greatest increases in its phenolic content and antioxidant capacity.