Application Of Supercritical Carbon Dioxide Research Articles

Dual-Parameter Prediction of Downhole Supercritical CO2 with Associated Gas Using Levenberg–Marquardt (LM) Neural Network

This research investigates the application of supercritical carbon dioxide (CO2) within carbon capture, utilization, and storage (CCUS) technologies to enhance oil-well production efficiency and facilitate carbon storage, thereby promoting a low-carbon circular economy. We simulate the flow of supercritical CO2 mixed with associated gas (flow rates 3–13 × 104 Nm3/d) in a miniature venturi tube under high temperature and high-pressure conditions (30–50 MPa, 120–150 °C). Accurate fluid property calculations, essential for simulation fidelity, were performed using the R. Span and W. Wagner and GERG-2008 equations. A dual-parameter prediction model was developed based on the simulation data. However, actual measurements only provide fluid types and measurement data, such as pressure, temperature, and venturi differential pressure, to determine the liquid mass fraction (LMF) and total mass flow rate (m), presenting challenges due to complex nonlinear relationships. Traditional formula-fitting methods proved inadequate for these conditions. Consequently, we employed a Levenberg–Marquardt (LM) based neural network algorithm to address this issue. The LM optimizer excels in handling complex nonlinear problems with faster convergence, making it suitable for our small dataset. Through this approach, we formulated dual-parameter model equations to elucidate fluid flow factors, analyzing the impact of multiple parameters on the LMF and the discharge coefficient (C). The resulting model predicted dual parameters with a relative error for LMF of ±1% (Pc = 95.5%) and for m of ±1% (Pc = 95.5%), demonstrating high accuracy. This study highlights the potential of neural networks to predict the behavior of complex fluids with high supercritical CO2 content, offering a novel solution where traditional methods fail.

Application of supercritical carbon dioxide to enhance the aroma of whole sorghum flour for use in 3D printing of sorghum cookies

Sorghum is a promising ingredient for new food products due to its high fiber content, slow digestibility, drought resistance, and gluten-free nature. One of the main challenges in sorghum-based products is the unpleasant aroma compounds found in grain sorghum. Therefore, in this study, sorghum flour was treated via supercritical carbon dioxide (SC-CO2) to remove undesired aroma compounds. The resulting SC-CO2-treated flours were used to generate dough for 3D food printing. At the optimized conditions, sorghum cookies were 3D-printed using 60 % water and a nozzle diameter of 1.5 mm. All dough samples produced with untreated and SC-CO2-treated sorghum flours exhibited shear-thinning behavior. Changing the treatment pressure (8–15 MPa) or temperature (40–60 °C) did not significantly affect the viscosity of the dough samples. Moreover, the sorghum cookie doughs had higher G′ and G″ values after the SC-CO2 treatments (G′ >G″). Doughs generated from flours treated at 15 MPa − 40 °C and 8 MPa − 60 °C showed lower adhesiveness compared to the ones produced from untreated flour, whereas 15 MPa − 60 °C treatment did not affect the adhesiveness. After baking, the 3D-printed cookies from SC-CO2-treated flour exhibited significantly lower redness (a*), but the hardness of the cookies was not affected by SC-CO2 treatment. Overall, the SC-CO2 treatment of sorghum flour did not negatively affect the quality parameters of the 3D-printed cookies while enhancing the aroma of the flour.

Feasibility and performance limitations of Supercritical carbon dioxide direct-cycle micro modular reactors in primary frequency control scenarios

This study investigates the application of supercritical carbon dioxide (S–CO2) direct-cycle micro modular reactors (MMRs) in primary frequency control (PFC), which is a scenario characterized by significant load fluctuations that has received less attention compared to secondary load-following. Using a modified GAMMA + code and a deep neural network–based turbomachinery off-design model, the authors conducted an analysis to assess the behavior of the reactor core and fluid system under different PFC scenarios. The results indicate that the acceptable range for sudden relative electricity output (REO) fluctuations is approximately 20%p which aligns with the performance of combined-cycle gas turbines (CCGTs) and open-cycle gas turbines (OCGTs). In S–CO2 direct-cycle MMRs, the control of the core operates passively within the operational range by managing coolant density through inventory control. However, when PFC exceeds 35%p, system control failure is observed, suggesting the need for improved control strategies. These findings affirm the potential of S–CO2 direct-cycle MMRs in PFC operations, representing an advancement in the management of grid fluctuations while ensuring reliable and carbon-free power generation.

Analysis and comparison of cooling performance, thermodynamic performance and system weight of different Brayton systems based on scramjet engine

The application of supercritical carbon dioxide (sCO2) closed Brayton cycle to scramjet engines is a very promising technology that can simultaneously relieve flight cooling pressure and provide electrical power. However, for scramjet engines, not only high efficiency and low fuel consumption are required, but also the size and weight of the cooling system need to be considered. In this study, the thermodynamic models for three typical sCO2 layouts, namely simple recuperated cycle (SR.C), recompression cycle (RC.C) and partial heating cycle (PH.C), are developed to conduct the performance comparison for finding the layout which is most suitable for the scramjet cooling application. The effects of the key parameters of the system on the thermodynamic and cooling performance, fuel consumption, and total mass of heat exchangers are analyzed, and the single-objective optimization of the system performance is carried out to provide a reference for selecting the appropriate layout. The results show that the PH.C has the lowest fuel consumption for cooling, followed by the RC.C and the SR.C. The RC.C shows the greatest potential in terms of net power output, followed by the SR.C and the PH.C. And the SR.C is the lightest, followed by the PH.C and the RC.C.

Modeling and program development of supercritical CO2 sub-channel based on Modelica language

The application of supercritical carbon dioxide (S-CO2) in small nuclear reactors is a new research direction with promising prospects. Most of the research on S-CO2 cooled reactors focuses on the design and optimization of core parameters, but few on detailed thermal and hydraulic analysis of the reactor interior using the sub-channel method. To supplement the lack of research in S-CO2 small nuclear reactors, this paper developed an S-CO2 cooled reactor two-dimensional sub-channel analysis model based on Modelica language. To verify the correctness of the model and program, the calculated results of the sub-channel program are compared with the results of KAIST MMR in Korea, the power deviation is less than 4%, the coolant temperature deviation is less than 7%, and the fuel rod temperature deviation is less than 10%. Based on the developed sub-channel model, the transient analysis is carried out, including reactor power increase, reactivity insertion, and coolant flow loss accidents, and then the safety performance of the reactor is evaluated. The transient response of the reactor under accident conditions is obtained, and the self-stability and self-adjustment characteristics are proved. This paper relies on theoretical modeling and program development methods, studying the sub-channel thermal-hydraulic characteristics of steady-state and transient conditions, which provides theoretical reference and program support for the study of the S-CO2 small nuclear reactor.

Application of CO2 Supercritical Fluid to Optimize the Solubility of Oxaprozin: Development of Novel Machine Learning Predictive Models.

Over the last years, extensive motivation has emerged towards the application of supercritical carbon dioxide (SCCO2) for particle engineering. SCCO2 has great potential for application as a green and eco-friendly technique to reach small crystalline particles with narrow particle size distribution. In this paper, an artificial intelligence (AI) method has been used as an efficient and versatile tool to predict and consequently optimize the solubility of oxaprozin in SCCO2 systems. Three learning methods, including multi-layer perceptron (MLP), Kriging or Gaussian process regression (GPR), and k-nearest neighbors (KNN) are selected to make models on the tiny dataset. The dataset includes 32 data points with two input parameters (temperature and pressure) and one output (solubility). The optimized models were tested with standard metrics. MLP, GPR, and KNN have error rates of 2.079 × 10−8, 2.173 × 10−9, and 1.372 × 10−8, respectively, using MSE metrics. Additionally, in terms of R-squared, they have scores of 0.868, 0.997, and 0.999, respectively. The optimal inputs are the same as the maximum possible values and are paired with a solubility of 1.26 × 10−3 as an output.

Computational fluid-dynamic investigation of a centrifugal compressor with inlet guide vanes for supercritical carbon dioxide power systems

A centrifugal compressor for large-scale supercritical carbon dioxide applications (∼50 MW) is analyzed by means of RANS simulations. The purposely designed compressor includes adjustable inlet guide vanes, an open impeller, and a wedge-shaped vaned diffuser. The upstream total state is located at 78.70 bar and 305.15 K, close to the thermodynamic critical point, whereby non-ideal effects and two-phase flows are significant. To account for these effects, the computational model implements a homogeneous equilibrium model (using pressure and specific enthalpy as state variables) complemented with a state-of-the-art equation of state explicit in the Helmholtz free energy and specific correlations for transport properties. It is found that the compressor can provide the entire pressure ratio required by the cycle (∼3.25) with high efficiency (87.9%, excluding parasitic losses). Three inlet vane rotations are considered: −10deg, 20deg, and 40deg. The preswirl has a limited effect on efficiency, which is reduced by 0.3% points away from choked conditions with vane rotation of 40deg. Nonetheless, the preswirl affects the extent of the two-phase region at the impeller intake, which has a detrimental impact on the compressor flexibility by setting an early choking.

Applications of Supercritical Carbon dioxide in Textile Finishing: A Review

Applications of Supercritical Carbon dioxide in Textile Finishing: A Review

Application of Supercritical Fluid Extraction (SFE) of Tocopherols and Carotenoids (Hydrophobic Antioxidants) Compared to Non-SFE Methods

Natural antioxidants have renewed value for human health and the food industry. Green labeling is becoming an important attribute for consumers and is impacting food processing and formulations. Clean label is another attribute that ranked third after the “free-from” claims and “a good source” of nutrient claims. Clean label attributes also are ranked higher than local, seasonal, and organic. Techniques that are able to preserve the valuable characteristics of natural antioxidants, while eliminating even trace amounts of solvent residues from their extraction and processing, are important. Supercritical fluids (SCF) are an effective green technology that can be adopted for extraction of natural antioxidants. This review is focused on the application of supercritical carbon dioxide (SCCO2) for extracting hydrophobic antioxidant compounds with an emphasis on oilseed crops and carrots. The information provided about extraction parameters helps to guide optimization of the yield of tocopherols and carotenoids. Pressure is the most effective parameter for the extraction yield of tocopherol among the other parameters, such as temperature, time, and CO2 flow rate. For carotenoid extraction, both pressure and temperature have a large impact on extraction yield. Higher yields of antioxidants, greater purity of the extracts, and larger retention of bioactivity are the main advantages of supercritical fluid extraction (SFE) in comparison to other conventional techniques. The benefits of SCF technology may open new opportunities for extracting valuable, natural and effective antioxidant compounds from food processing co-streams for use as bioactive compounds.

Waterless sterilization and cleaning of sheep wool fiber using supercritical carbon dioxide

There is increasing concern regarding the existing sheep wool processing technology in the textile industry owing to the enormous volume of toxic effluents generated. The application of supercritical carbon dioxide (scCO2) in sheep wool processing is cleaner and increases wool fiber production while avoiding toxic effluent generation. scCO2 is a novel clean technology that can be utilized in sheep processing for sterilization, cleaning, and drying sheep wool at the same time. In the present study, scCO2 was used to treat sheep wool with varying pressure, temperature, and treatment time. These parameters influence the scCO2 treatment of sheep wool fiber through the inactivation of microorganisms and improvement of the whiteness index. The identification of bacteria in sheep wool was carried out based on biochemical analysis by molecular means, using 16s rRNA sequencing. It was found that scCO2 completely inactivated the microorganisms present in sheep wool and potentially enhanced the percentage whiteness index at the highest pressure of 30 MPa, temperature of 80°C, and treatment time of 80 min. Several analytical methods were employed to assess the physicochemical, thermal, and morphological properties of untreated and scCO2 treated sheep wool fibers. The results show that scCO2 effectively removes the impurities and completely inactivates the microorganisms present in sheep wool. The findings of the present study reveal that scCO2 can be utilized as an alternative treatment technology for sheep wool processing in the textile industry.

Exergoeconomic perspective to evaluate and optimize supercritical carbon dioxide coal-fired power generation system

The application of supercritical carbon dioxide (SCO2) Brayton cycle to coal-fired power generation system has attracted increasing attention since 2018. In this study, the SCO2 coal-fired power generation system is evaluated and optimized from the exergoeconomic perspective. The purpose is to conduct comprehensive and in-depth analysis of this system. The simulated model of the studied system and corresponding exergoeconomic model are initially established. Subsequently, the cost formation process of system is revealed and the exergoeconomic performances of components and overall system are evaluated. The effects of five crucial operation parameters on exergoeconomic performance evaluation parameters are explored. Finally, the exergoeconomic performance of the studied system is optimized and compared with the preliminary design case. The results show that the unit exergy cost of coal, flue gas, SCO2, shaft work, and electricity are 4.705 $/GJ, 6.586 $/GJ, 9.329 $/GJ, 10.175 $/GJ, and 10.331 $/GJ respectively. Design changes should firstly be targeted to superheat cooling wall and high temperature recuperator due to its higher expense cost rate. Moreover, for the overall system, the exergy decrease cost rate is dominant and the total product unit cost is 15.988 $/GJ under preliminary design case. In parametric analysis, importantly, the method of increasing maximum operation temperature/pressure to reduce total product unit cost is limited. From exergoeconomic optimization results, for the system with high facility cost, a moderate decrease of maximum operation temperature/pressure can achieve the reduction of total product unit cost. The ultimate conclusion indicates that the selection criterion of operation parameters is to maintain the balance of exergy efficiency and total facility cost of the overall system. In conclusion, this study could provide reference to the construction of real SCO2 coal-fired power generation system.

Implications of Phase Change on the Aerodynamics of Centrifugal Compressors for Supercritical Carbon Dioxide Applications

Abstract Closed Joule–Brayton cycles operating with carbon dioxide in supercritical conditions (sCO2) are nowadays collecting a significant scientific interest, due to their high potential efficiency, the compactness of their components, and the flexibility that makes them suitable to exploit diverse energy sources. However, the technical implementation of sCO2 power systems introduces new challenges related to the design and operation of the components. The compressor, in particular, operates in a thermodynamic condition close to the critical point, whereby the fluid exhibits significant non-ideal gas effects and is prone to phase change in the intake region of the machine. These new challenges require novel design concepts and strategies, as well as proper tools to achieve reliable predictions. In this study, we consider an exemplary sCO2 power cycle with the main compressor operating in proximity to the critical point, with an intake entropy level of the fluid lower than the critical value. In this condition, the phase change occurs as evaporation/flashing, thus resembling cavitation phenomena observed in liquid pumps, even though with specific issues associated with compressibility effects occurring in both the phases. The flow configuration is therefore highly nonconventional and demands the development of proper tools for fluid and flow modeling, which are instrumental for the compressor design. The paper discusses the modeling issues from the thermodynamic perspective, then highlighting their implications on compressor aerodynamics. We propose tailored models to account for the effect of the phase change in 0D mean-line design tools as well as in fully three-dimensional (3D) computational fluid-dynamic (CFD) simulations: the former was previously validated for sCO2 compressors, the latter is validated in this paper against experiments of compressible flows of supercritical sCO2 in nozzles. In this way, a strategy of investigation is built-up as a combination of mean-line tools, industrial design experience, and CFD for detailed flow analysis. The investigation reveals that the potential onset of the phase change might alter significantly the performance and operation of the compressor, both in design and in off-design conditions, according to three main mechanisms: incidence effect, front-loading, and channel blockage.

Supercritical Carbon Dioxide Applications in Food Processing

There are global trends for developing green and sustainable technologies in food processing, due to the growing awareness of the importance of environmental preservation and the consumer demand for natural high-value food products. Meeting these particular requirements, supercritical carbon dioxide (SC-CO2) has emerged as an innovative and promising technology for the processing of food ingredients and products. Over the last two decades, applications of SC-CO2 have attracted much attention and made great advancements at both laboratory and industrial level. These advances include the extraction of target bioactive compounds from various food matrices, microencapsulation, or extrusion to produce fine particles, and the inactivation of pathogenic and spoilage microorganisms and endogenous enzymes for food preservation. An example of successfully applying SC-CO2 at the commercial level is the decaffeination of coffee. In this article, an overview of the SC-CO2 applications in food processing including extraction, transformation, preservation, and drying are presented. For each application category, principles, processing parameters, characteristics, and latest applications are critically reviewed.

Use of high-power ultrasound combined with supercritical fluids for microbial inactivation in dry-cured ham

The aim of this study was to analyze the application of supercritical carbon dioxide combined with high-power ultrasound (SC-CO2 + HPU) and the use of a saline solution (SS; 0.85% NaCl) on the microbial inactivation and the quality of dry-cured ham. The effect of temperature, pressure and treatment time was studied using RSM. Physicochemical analyses were carried out after the treatments and during refrigerated storage (30 days / 4 °C). The most significant inactivation of Escherichia coli (3.62 ± 0.20-log CFU/g) was obtained using the SC-CO2 + HPU + SS (25 MPa, 46-°C and 10-min), with temperature being the most important process variable. Fat content showed a significant (p < 0.05) reduction (46%) after the SC-CO2 + HPU treatment. The breakage of the muscle fibers, the disorganization in the myofibrils, as well as the enlargement of the interfibrillar spaces led to the ham softening (avg 26.5%). No significant (p > 0.05) changes in color, texture or pH were found during storage. Thus, ultrasonic-assisted SC-CO2 could be used, in combination or not with SS, to improve the shelf of dry-cured ham. Industrial relevanceSupercritical carbon dioxide (SC-CO2) inactivation technology has been shown to be highly efficient at reducing different bacteria in liquid media with minimum effect on food quality. This technology is barely applied to solid products and its use is limited by the long processing times and reduced inactivation capacity. The application of high-power ultrasound (HPU) leads to a shorter process time. This technology is useful for the inactivation of ham microbiota and inoculated E.coli. A liquid medium surrounding the treated solid can enhance microbial inactivation for the purposes of improving the effect of ultrasound cavitation, while only minimally affecting the quality of the samples (color, texture, fat and moisture contents).

Industrial Application of Supercritical Carbon Dioxide for Natural Products Extraction, and Decaffeination Technology for Coffee Beans

Industrial Application of Supercritical Carbon Dioxide for Natural Products Extraction, and Decaffeination Technology for Coffee Beans

Microencapsulation of eucalyptol in polyethylene glycol and polycaprolactone using particles from gas-saturated solutions.

Eucalyptol is the natural cyclic ether which constitutes the bulk of terpenoids found in essential oils of Eucalyptus spp. and is used in aromatherapy for treatment of migraine, sinusitis, asthma and stress. It acts by inhibiting arachidonic acid metabolism and cytokine production. Chemical instability and volatility of eucalyptol restrict its therapeutic application and necessitate the need to develop an appropriate delivery system to achieve extended release and enhance its bioactivity. However, the synthesis method of the delivery system must be suitable to prevent loss or inactivation of the drug during processing. In this study, supercritical carbon dioxide (scCO2) was explored as an alternative solvent for encapsulation and co-precipitation of eucalyptol with polyethylene glycol (PEG) and/or polycaprolactone (PCL) using the particles from gas-saturated solution (PGSS) process. Polymers and eucalyptol were pre-mixed and then processed in a PGSS autoclave at 45 °C and 80 bar for 1 h. The mixture in scCO2 was micronized and characterized. The presence of eucalyptol in the precipitated particles was confirmed by infrared spectroscopy, gas chromatography and mass spectrometry. The weight ratios of PEG–PCL blends significantly influenced loading capacity and encapsulation efficiency with 77% of eucalyptol encapsulated in a 4 : 1 composite blend of PEG–PCL. The particle size distribution of the PGSS-micronized particles ranged from 30 to 260 μm. ScCO2 assisted microencapsulation in PEG and PCL reduced loss of the volatile drug during a two-hour vaporization study and addition of PCL extended the mean release time in simulated physiological fluids. Free radical scavenging and lipoxygenase inhibitory activities of eucalyptol formulated in the PGSS-micronized particles was sustained. Findings from this study showed that the scCO2-assisted micronization can be used for encapsulation of volatile drugs in polymeric microparticles without affecting bioactivity of the drug.

Mini review: Application of supercritical carbon dioxide in extraction of propolis extract

Propolis is a resinous substance produced by bees functioned to seal holes, exclude draught, protect against contamination and external intruders inside their hives has been substantially studied and reported to have numerous health properties such as antiseptic, antifungal, antibacterial, antiviral, anti-inflammatory and antioxidant characteristics. Propolis cannot be utilized as raw material, due to its complex mixture of compounds. Hence it must be separated by the extraction process. Extraction targets to removes the inert compounds in the propolis sample and preserves the flavonoids and polyphenolic fraction. The most common technique used in propolis extraction is solvent extraction that involves the use of solvents such as ethanol, water, hexane, ethyl-acetate and chloroform. However, this conventional technique has some drawbacks including strong residual flavour, possible adverse reactions, harmful to the environment, low quality of the extract and long process period requirement. Supercritical carbon dioxide (SC-CO2) is one of the alternative techniques to conventional extraction that was reported to be an excellent method to purify and fractionate bioactive compounds from natural sources. SC-CO2 extraction was first introduced for analytical application because of the demand to reduce organic solvent utilization in a laboratory environment. It has now become a favourite technique in extraction, fractionation, refinement, and deodorization of natural sample matrices in laboratory scale and industrial scale. Carbon dioxide is an ideal supercritical solvent due to its non-toxic, non-polluting, non-flammable, recoverable and environmentally benign properties. Therefore, this mini review aims to discuss the application of supercritical carbon dioxide extraction specifically on propolis sample starting with a brief introduction on propolis, methods of propolis extraction, the principle of SC-CO2 extraction, application of SC-CO2 in propolis extraction, advantages of SC-CO2 extraction and lastly comparison between SC-CO2 and conventional extraction techniques.

Laboratory Evaluation of Different Modes of Supercritical Carbon Dioxide Miscible Flooding for Carbonate Rocks

Summary Field application of supercritical carbon dioxide (sc-CO2) miscible flooding continues to grow. Optimization of sc-CO2 injection during miscible-flooding modes represents one of the dominant factors affecting its performance in carbonate oil reservoirs. The main objective of this study was to investigate the effect of different modes of sc-CO2 miscible injection on oil recovery and injectivity in carbonate rocks. Several modes of sc-CO2 injection were investigated, including continuous CO2 miscible flooding, water-alternating-gas (WAG), and tapered-WAG injection. Five coreflooding experiments were conducted to evaluate oil recovery for different modes of sc-CO2 injection under reservoir conditions. Composite cores of 25-cm length from a specific, producing carbonate reservoir were used in the study. Both horizontal- and vertical-coreflooding experiments of continuous-sc-CO2-injection mode were performed to compare oil recovery and injectivity during sc-CO2 flooding. Horizontal-coreflooding experiments under WAG mode were performed at pore pressures of 3,200 and 3,800 psi. The experimental results indicate that tertiary oil recovery was influenced significantly by different sc-CO2-injection modes and the direction of displacement. Original oil in cores was recovered at 18.4 and 26.74% for horizontal and vertical experiments of continuous-sc-CO2-injection modes, respectively. In horizontal-WAG experiments with different pore pressures, higher oil recovery was observed at a pore pressure of 3,800 psi compared with 3,200 psi. The marginal increase in incremental oil recovery indicates that pressure increase beyond 3,200 psi will not have a significant effect. The injectivity of different sc-CO2-injection modes is reported in this paper.

Viability of Molds and Bacteria in Tempeh Processed with Supercritical Carbon Dioxides during Storage.

Application of supercritical carbon dioxide for processing of food products has an impact on microbial inactivation and food quality. This technique is used to preserve tempeh due to no heat involved. The quality of tempeh is highly influenced by mold growth because of its role in forming a compact texture, white color, and functional properties as well as consumer acceptance. This study aims to observe viability of molds and bacteria in tempeh after processed with supercritical CO2 and to determine the best processing conditions which can maintain mold growth and reduce the number of bacteria in tempeh. For that purpose, tempeh was treated using high pressure CO2 at 7.6 MPa (supercritical CO2) and at 6.3 MPa (sub/near supercritical CO2) with incubation period of 5, 10, 15, and 20 min. The best treatment obtained was used to process tempeh for storage study. The results showed that there was a significant interaction between pressure and incubation period for bacterial and mold viability at ρ>0.05. Reduction of bacteria and molds increased with longer incubation period. Molds were undetectable after treatment for 20 min with either supercritical CO2 or sub-supercritical, and bacteria significantly reduced up to 2.40 log CFU/g. On the other hand, sub-supercritical CO2 for 10 min was the best processing method because molds survived 4.3x104 CFU/gram after treatment and were able to grow during storage at 30°C, producing white mycelium as indicated by increasing the L⁎ color value and tempeh acceptability. The inactivation of mold was reversible causing it to grow back during storage under suitable conditions. Tempeh matrix composition can provide protection against the destructive effects of supercritical CO2. Gram-positive bacteria were more resistant than Gram-negative. In conclusion, sub-supercritical CO2 can act as a method of cold pasteurization of tempeh and can be used as an alternative method to preserve tempeh.

Disinfection of ancient paper contaminated with fungi using supercritical carbon dioxide

Abstract Fungi continue to be the main cause of biodeterioration in libraries. In addition to degrading paper, fungi are an important health issue for librarians and even library users. The aim of this study was to investigate the application of supercritical carbon dioxide (SCCO 2 ) to ancient paper contaminated with fungi. For this purpose, SCCO 2 was applied in two processes to treat samples of paper pieces: addition of 4% and 8% ethanol (w/w) at a pressure of 150 bar and temperature of 40 °C for 1 hour. Control samples (no processing) and processed samples were directly plated onto culture media to evaluate the frequency of fungal growth. Morphological and molecular analysis of the 294 samples showing mold growth on paper revealed that Aspergillus niger , Aspergillus flavus , and Eurotium amstelodami were the most frequently isolated fungi. In the control group, 47.6% of the samples were contaminated with fungi. This percentage was only 1.9% after treatment with both processes. The difference between unprocessed control samples and samples treated under the two conditions was statistically significant ( P