Effect Of High Pressure Carbon Dioxide Research Articles

Effects of High-Pressure Carbon Dioxide on the Sensory and Chemical Properties of Dried Dates and Its Toxicity against Galleria mellonella (L.) and Plodia interpunctella (Hübner)

The use of chemical pesticides can have many detrimental side effects, including environmental pollution, and be a threat to human health. Carbon dioxide (CO2) treatment, a relatively new method for storage pest management, can replace harmful chemicals. Dates, an important food worldwide, contains many minerals, fiber, and a variety of vitamins and are an important dried fruit export from Iran annually. Thus, control of the pests of dried dates by using eco-friendly agents that do not affect quality features are critical. In this study, larval mortality of the Indian meal moth (Plodia interpunctella (Hübner)) and the greater wax moth (Galleria mellonella (L.)), two key pests of stored products, especially dried dates, was studied after exposure to different CO2 pressures within 24 h. Mortality percentages of the third-instar larvae of both pests were increased with an increase in CO2 pressure. Sensory tests on the qualitative characteristics of the dates revealed that CO2 pressures did not affect their aroma, color, sweetness, sourness, crispness, firmness, and overall acceptance. The highest tested pressure (33.4 mol%) of CO2 also had no significant effects on the chemical properties of the date samples, including moisture content, pH, acidity, Brix value, reducing sugar, and total sugar. We conclude that atmospheric CO2 gas can provide a cost-effective and environmentally friendly method for controlling the insect pests of dried dates in addition to preserving their sensory and quality properties.

High-pressure carbon dioxide treatment and vacuum packaging alleviate the yellowing of peeled Chinese water chestnut (Eleocharis tuberosa)

This work evaluated the effects of high-pressure carbon dioxide (HPCD) treatment and vacuum packaging on the yellowing of peeled Chinese water chestnut (CWC) during storage. The changes in color, enzymatic activities, total phenolic content and malondialdehyde contents were assessed in peeled CWC. The results showed that vacuum packaging alone, atmospheric packaging after HPCD treatment, and vacuum packaging after HPCD treatment (HPCD+VP) could significantly delay the yellowing of fresh-cut CWC to varying degrees. The total phenolic content was lower (68%) in HPCD+VP samples than that of control. Compared to control, the enzymatic activities such as phenylalanine ammonia-lyase, polyphenol oxidase and lipoxygenase decreased by 76% (12th day), 24% (6th day) and 19% (6th day) respectively in HPCD+VP samples. HPCD and vacuum packaging could efficiently inhibit several enzymes activities. Our study exhibited that HPCD+VP treatment delayed the yellowing of fresh-cut CWC by reducing the phenylpropanoid metabolism pathway activity and cell membrane peroxidation.

Effects of high-pressure carbon dioxide on microbial quality and germination of cereal grains and beans

Decontamination of low aw foods without impairing the food quality is challenging, particularly for sprouting seeds. This study aimed to explore the lethality of high pressure carbon dioxide (HPCD) to Salmonella enterica, E. coli AW1.7, A. niger, P. roquforti, and Fusarium on beans, cereal grains, and ground pepper. The optimal antimicrobial effect of HPCD was achieved by equilibration of the aw to 0.75, followed by soaking in water and treatments with water-saturated CO2. HPCD reduced the viable cell counts of E. coli and Salmonella by 3–10 log(CFU/g), and prevented fungal growth during 10 d of incubation. More than 90% of mung beans germinated but the germination of oats was impaired after fungicidal or bactericidal treatments with HPCD. Overall, HPCD can be a promising antimicrobial treatment but treatment parameters need to be optimized for each type of seed.

Effect of high-pressure carbon dioxide treatment on browning inhibition of fresh-cut Chinese water chestnut (Eleocharis tuberosa): Based on the comparison of damaged tissue and non-damaged tissue

In this paper, the effect of high-pressure carbon dioxide (HPCD) inhibiting the browning of fresh-cut Chinese water chestnut (CWC) was explored by comparing the differences between damaged and non-damaged tissues. The results showed that the browning of fresh-cut CWC could be effectively inhibited by 2 and 4 MPa treatment, and with these conditions, the microbial load was kept at a low and stable level during the whole storage period. In damaged tissues, the phenylalanine ammonia-lyase (PAL) activity was decreased, thus cutting off the accumulation of naringenin and eriodictyol (only slightly detected at 1 MPa). In non-damaged tissues, the activities of polyphenol oxidase (PPO), peroxidase (POD), and PAL were significantly increased to overcome the treatment stress. The structural change of PAL proved its activity reduction. The mechanism of browning inhibition could be explained by direct inactivation of PAL in damaged tissue and indirect regulation of stress resistance response in non-damaged tissue.

High-pressure supercritical carbon dioxide uses to inactivate Escherichia coli in pumpkin puree

Coli ATCC 25922 inactivation was studied to determine the effect of high-pressure carbon dioxide (HPCD) process on pumpkin puree. Experiments were performed using a batch HPCD system at three conditions of pressure (7.5 MPa, 17.5 MPa and 27.5 MPa) at 32 °C. Afterwards, at the best experimental condition (27.5 MPa – 275 bar), a kinetic was performed to assess inactivation of microorganisms over time (from 1 to 8 h). The physicochemical characteristics (pH, total soluble solids – TSS, titratable acidity – TA, total carotenoids, total reducing sugars – TRS, moisture and optical microscopy) of the pumpkin puree were also evaluated. HPCD with acidification increases bacterial efficacy of treatments, as well as significant changes in physicochemical parameters. HPCD treatment reduced the microbial load moderately in all experiments, by a maximum of approximately 3.17 log cycles in 8 h of process at 27.5 MPa (275 bar). Optical microscopy showed no difference in cell wall, just in starch which was expected by cooking.

High-Pressure Carbon Dioxide Used for Pasteurization in Food Industry

The demand for safe, high-quality food has greatly increased, in recent times. As traditional thermal pasteurization can significantly impact the nutritional value and the color of fresh food, an increasing number of nonthermal pasteurization technologies have attracted attention. The bactericidal effect of high-pressure carbon dioxide has been known for many years, and its effect on food-related enzymes has been studied. This novel technology has many merits, owing to its use of relatively low pressures and temperatures, which make it a potentially valuable future method for nonthermal pasteurization. For example, the inactivation of polyphenol oxidase can be achieved with relatively low temperature and pressure, and this can contribute to food quality and better preserve nutrients, such as vitamin C. However, this novel technology has yet to be developed on an industrial scale due to insufficient test data. In order to support the further development of this application, on an industrial scale, we have reviewed the existing information on high-pressure carbon dioxide pasteurization technology. We include its bactericidal effects and its influence on food quality. We also pave the way for future studies, by highlighting key areas.

A model of cement-formation interface failure length in supercritical CO2-ECBM and storage injection well considering the coal swelling effect under high pressure

The swelling effect of high-pressure carbon dioxide (CO2) in coal seam is obvious. In the restrained deep formation, it is converted to stress acting on the wellbore and the caprock. The action stress is concentrated near the wellbore and poses a threat to the cement-formation interface. Due to interface failure to micro-annulus, wellbore integrity will be lost and this will have an impact on carbon dioxide-enhanced coalbed methane recovery (CO2-ECBM) and storage. In this paper, the pseudo-steady pressure distribution and steady pressure distribution of CO2 injection process were established after considering the change in permeability of coal seam injected with high-pressure supercritical CO2, and the vertical stress distribution model was derived. A one-dimensional radial numerical simulation formed by iterative method was established. A model for calculating the failure length at the cement-formation interface is obtained, and the shear stress and debonding length at the interface at various injection rates and times are calculated. The results show that the shear stress on the cement-formation interface has the maximum magnitude on the height of the interface between coal seam and caprock. The shear stress generated by coal swelling may break the fragile cement-formation interface into a narrow debonding interface. The injection rate has an influence on the interface failure length. For the same total injection amount, low injection rate is beneficial to protect the cement-formation interface integrity. This study provides a reference for the design of maximum injection speed for CO2-ECBM and storage to avoid leakage.

Effect of high‐pressure carbon dioxide on the quality of cold‐ and hot‐break tomato pulps

High-pressure carbon dioxide (HPCD) has been considered as an alternative to thermal treatment in food processing. This effect of HPCD on microorganism, physicochemical properties, and lycopene isomerization of cold- and hot-break tomato pulps was investigated. The microorganism in the cold-break tomato pulp was effectively inactivated by HPCD at 10 MPa, showing a decrease with increasing the treatment time. HPCD retained better color and more aroma volatiles as compared to thermal treatment. The consistency of cold- and hot-break tomato pulps was improved by HPCD processing. For the cold-break tomato pulp, HPCD had a significant positive effect on the isomerization of lycopene. Titratable acid of HPCD-treated tomato pulp increased, while pH, soluble solid content were stable. The results above demonstrated that HPCD has greater advantages to retain the quality of cold- and hot-break tomato pulps and could be a promising nonthermal alternative technique for tomato products. Practical applications Thermal processing of tomato products is mostly used method to prevent microbial spoilage, but has deleterious influence on the sensorial quality and nutritional properties. High-pressure carbon dioxide (HPCD) has been considered as an alternative to thermal treatment in food processing. This research assessed the applicability of HPCD as a method of preserving tomato pulps, including natural microorganisms and lycopene isomerization which are critical to understand the prospects for tomato pulp processing.

Effect of high-pressure carbon dioxide on the aggregation and conformational changes of polyphenol oxidase from apple (Malus domestica) juice

This study investigated the effect of different states of CO2 on the activity and structural modification of purified polyphenol oxidase (PPO) from apple juice. CO2 in critical and supercritical states strongly inhibited the PPO activity up to 64.88% and 3.20%, respectively. Dynamic light scattering analysis showed that the two peaks depolymerised into three peaks in the critical state, demonstrating the dissociation and aggregation of small particles. Circular dichroism analysis revealed that the secondary structure deformed because of the loss of α-helix contents in the critical and super critical CO2 states. Fluorescence intensity dramatically decreased to 251.3 (λmax 312) in the critical state, showing unfolding of PPO molecules thereby resulting in quenching and blue shifting of λmax. Electrophoresis indicated that large molecular aggregates did not run into the gel at supercritical state. Hence, HP-CO2 treatment in critical and super critical states could induce the aggregation, deformation and structural changes which might be the causes of PPO inactivation. “Polyphenol oxidation (PPO) is the enzyme that initiates the browning reaction and deteriorates the quality of fruit juices”. High pressure carbon dioxide (HP-CO2) technology is a promising technique to obtain high quality apple juices with low enzyme activity. This study analyzed the effects of different states of carbon dioxide gases under HPCD on the activity, aggregation, deformation and structural changes of PPO from apple juice. Available findings provided in this study will benefit the food industry.

Peridynamics simulation of rock fracturing under liquid carbon dioxide blasting

Liquid carbon dioxide blasting technology as a new environmentally safe rock cracking technology has been widely used in mining, enhancing the permeability of coal seam, road construction, and other fields. In this study, a liquid carbon dioxide blasting experiment was conducted on a concrete specimen of size 500mm×500mm×400 mm firstly, and the crack distribution and blast hole morphology were observed. Then, the peridynamics model of rock fracturing under liquid carbon dioxide blasting was established, and the crack propagation in liquid carbon dioxide blasting and the influence of explosion pressure and numbers and radii of releasing holes on the liquid carbon dioxide blasting effects were analyzed. The results showed that the broken concrete specimen had no obvious smash district and the direction of crack propagation was perpendicular to that of carbon dioxide release after liquid carbon dioxide blasting. The failure of the specimen was only caused by the blasting stress wave, and the quasi-static effect of high-pressure carbon dioxide did not have sufficient time to play its role. With an increase in the stress wave strength and the numbers and radii of releasing holes, the fracturing velocity of liquid carbon blasting will increase. The cracks produced by liquid carbon dioxide blasting were mainly distributed in the middle of the adjacent releasing holes. The research results had a good guiding significance for understanding the mechanism of liquid carbon dioxide rock breaking and optimizing and improving the liquid carbon dioxide fracturing device.

CO2 Induced Foaming Behavior of Polystyrene near the Glass Transition

This paper examines the effect of high-pressure carbon dioxide on the foaming process in polystyrene near the glass transition temperature and the foaming was studied using cylindrical high-pressure view cell with two optical windows. This technique has potential applications in the shape foaming of polymers at lower temperatures, dye impregnation, and the foaming of polystyrene. Three sets of experiments were carried out at operating temperatures of 50, 70, and 100°C, each over a range of pressures from 24 to 120 bar. Foaming was not observed when the polymer was initially at conditions below Tg but was observed above Tg. The nucleation appeared to occur randomly leading to subsequent bubble growth from these sites, with maximum radius of 0.02–0.83 mm. Three models were applied on the foaming experimental data. Variable diffusivity and viscosity model (Model C) was applied to assess the experimental data with the WLF equation. The model shows very good agreement by using realistic parameter values. The expansion occurs by diffusion of a dissolved gas from the supersaturated polymer envelope into the bubble.

Understanding drug release from PCL/gelatin electrospun blends.

Electrospinning is one of the efficient processes to fabricate polymeric fibrous scaffolds for several biomedical applications. Several studies have published to demonstrate drug release from electrospun scaffolds. Blends of natural and synthetic electrospun fibers provide excellent platform to combine mechanical and bioactive properties. Drug release from polymer blends is a complex process. Drug release from polymer can be dominated by one or more of following mechanisms: polymer erosion, relaxation, and degradation. In this study, electrospun polycaprolactone (PCL)-gelatin blends are investigated to understand release mechanism of Rhodamine B dye. Also, this article summarizes the effect of high-pressure carbon dioxide on drug loading and release from PCL-gelatin fibers. Results indicate that release media diffusion is a dominant mechanism for PCL-gelatin electrospun fibers. Thickness of electrospun mat becomes critical for blends with gelatin. As gelatin is highly soluble in water and has tendency of gelation, it affects diffusion of release media in and out of scaffold. This article is a key step forward in understanding release from electrospun blends.

Synergetic effects of high-pressure carbon dioxide and nisin on the inactivation of Escherichia coli and Staphylococcus aureus

Abstract Synergetic effects of high-pressure carbon dioxide (HPCD) and nisin on Escherichia coli and Staphylococcus aureus were evaluated. Changes in morphology, interior structure, and membrane permeability were analyzed by scanning and transmission electron microscopy, and flow cytometry. Synergetic effects were found, especially in S. aureus. HPCD alone or with nisin led to morphological and intracellular alterations in both bacteria, but nisin alone led to these damages only in S. aureus . A positive correlation between membrane damage and inactivation was found, but ratios of inactivation were higher, probably because of viable but non-culturable state. Mechanisms were proposed for synergism: for E. coli , outer membrane was damaged first by HPCD, and then HPCD and nisin jointly acted on and destroyed the cytoplasmic membrane, leading to further intracellular damage by HPCD; for S. aureus , HPCD and nisin acted on the cytoplasmic membrane together leading to cell death. Industrial Relevance Escherichia coli and Staphylococcus aureus are two common microorganisms, which exist widely in the environment and easily contaminate food such as vegetables and dairy products, respectively. Considering heat treatment may destroy some heat-sensitive quality of the products, this study evaluated synergetic effects of high-pressure carbon dioxide (HPCD) combined with the bacteriocin nisin. The investigations provided evidence for potentially combined application of HPCD and nisin to help keep food safe in the industry.

High Pressure Carbon Dioxide pasteurization of coconut water: A sport drink with high nutritional and sensory quality

High Pressure Carbon Dioxide (HPCD) treatment was applied to the pasteurization of coconut water in order to guarantee both its microbial stability and preserve its nutritional and sensory attributes. It was demonstrated that 120bar, 40°C, 30min were the optimal process conditions to induce a 5 Log(CFU/ml) reduction of mesophilic microorganisms, lactic acid bacteria, yeasts and molds and a 7 Log reduction of the total coliforms. The effect of HPCD on the quality traits of coconut water were investigated by means of physical–chemical and sensory analyses and compared to the Heat Pasteurized (HP, 90°C, 1min) and Fresh Untreated (FU) product. No differences in the basic chemical composition, vitamins and amino acids, were detected between HPCD and FU products. However, differences in the volatile compounds present in the three products were clearly distinguishable; HPCD resulted in a reduction of most of the volatile fractions while HP induced the formation of compounds with a toasted and malty aroma. Nevertheless, few sensory differences were perceived between the FU and the HPCD coconut water, and both were clearly differentiated from the HP product.

Inactivation of natural microorganisms in litchi juice by high-pressure carbon dioxide combined with mild heat and nisin

The individual and combined effects of high-pressure carbon dioxide (HPCD), mild heat (MH) and nisin (200 ppm) on the inactivation of natural microorganisms, including aerobic bacteria (AB), yeasts and molds (Y&M), in litchi juice were evaluated. The samples were treated at a pressure of 10 MPa and temperatures of 32, 42 or 52 °C for 5, 10, 15, 20, 25 or 30 min. Temperature played a prominent role in the inactivation of both AB and Y&M when combined with HPCD, particularly for AB at 52 °C and Y&M at temperatures ≥42 °C. Nisin increased the susceptibility of AB to the combined treatment of HPCD and MH (HPCD + MH). A reduction of 4.19 log cycles was achieved by HPCD + MH at 52 °C for 15 min, and complete inactivation of AB was obtained by combination of HPCD, MH and nisin (HPCD + MH + nisin). No significant effect of nisin was found on the inactivation of Y&M.

Effects of high-pressure carbon dioxide on proteins and DNA in Escherichia coli

Protein changes in Escherichia coli, when subjected to high-pressure carbon dioxide (HPCD) at 10 MPa and 3 °C for 5-75 min, were assessed using the Bradford method, 2D electrophoresis (2-DE) and liquid chromatography-electrospray ionization-MS-MS (LC-ESI-MS-MS). The changes in DNA in E. coli under the same conditions were also investigated by using flow cytometry with propidium iodide and acridine orange, agarose gel electrophoresis (AGE) and the comet assay. The results showed that HPCD induced leakage loss of the proteins and DNA of E. coli as a function of treatment time. With regard to the protein changes, 182 proteins in the 2-DE profile were not found in the HPCD-treated E. coli. Among 20 selected protein spots exhibiting significant changes in intensity, 18 protein spots were identified as 15 known proteins and two as hypothetical proteins. These proteins were involved in cell composition, energy metabolism pathways, nucleic acid metabolism, global stress regulation and general metabolism. The DNA denaturation of E. coli induced by HPCD was demonstrated in this study for the first time to our knowledge, and the denaturation was enhanced by increasing treatment time. However, HPCD did not cause DNA degradation, as suggested by both AGE analysis and the comet assay.

Effects of high-pressure carbon dioxide on the demulsification of O/W emulsion

A new process for the demulsification of oil-in-water (O/W) emulsion with high-pressure carbon dioxide (CO2) was proposed. For the confirmation of the concept, demulsification of O/W emulsion formed with a nonionic surfactant, Tween 20, was conducted. The behavior of O/W emulsion under high-pressure CO2 was examined with a visual observation and an electrical conductivity measurement of the emulsions. Efficiency of the demulsification was evaluated by the oil content of water-rich phases and the amount of water-rich phases separated from the emulsion by the creaming of the oil phases. Experimental results revealed that the high-pressure CO2 acts as a swelling reagent that lowers the density of the dispersed oil phase to induce the floatation of the oil droplet that leads to an efficient demulsification.

AC complex impedance measurement of comb-like type polyether electrolytes under high-pressure carbon dioxide

The effect of high-pressure carbon dioxide on ionic conductivity for comb-like type polyether electrolytes based on oligo(oxyethylene glycol) methacrylate with lithium triflate, LiCF 3SO 3, has been investigated for the first time. Our investigations have focused on the correlation between the segmental motion of the polymer side chains and the efficiency of ion transport under supercritical carbon dioxide (scCO 2) conditions. Consequently, the ionic conductivity under the condition of 10 MPa and 40 °C CO 2 sample was more than 30 times elevated compared with the original one. The improvement of ionic conductivity is attributed to an increase in the polymer segmental motion via a decrease in activation volume and enhanced the number of charge carriers. The temperature dependence of log σ followed Vogel–Tamman–Fulcher (VTF) equation. However, the pressure dependence under scCO 2 condition was ascribed to the Arrhenius behavior resulting in an increase of the ionic conductivity with increasing the pressure.

Effects of high-pressure carbon dioxide on Escherichia coli in nutrient broth and milk

Bactericidal effects of high-pressure carbon dioxide against Escherichia coli were studied under 100, 75, 50 and 25 bar at 20°C, 30°C and 40°C. E. coli suspended in nutrient broth (NB, pH=6.75) was inactivated under 100, 75, 50, and 25 bar CO 2 treatments for 50, 65, 100, and 140 min at 30°C, respectively. Acidification of nutrient broth by dissolved CO 2 alone might account for the bactericidal effect under pressure. E. coli was inactivated in NB with initial pH 5.50 and 4.5 at 100 bar for 80 and 95 min, respectively. Treatment at 100 bar CO 2 pressure for 6 h caused a decrease of 6.42 and 7.24 log cycles in whole and skim milk, respectively.

Lethal effect of high-pressure carbon dioxide on a bacterial spore

To develop a novel and effective method for sterilization of bacterial spores, we examined the lethal effect of high-pressure CO 2 on spore cells of Bacillus megaterium at various pressures and temperatures and for various treatment times. The bactericidal effect was found to be enhanced with increasing temperature and treatment time. Interestingly, there was an optimum pressure in the subcritical region of CO 2 which gave the maximum inactivation effects. Under the appropriate conditions of 58 atm, 60°C and 30 h, the survival ratio of the bacterial spore could be reduced to about 10 −7.