Continuous inactivation of alkaline phosphatase and Escherichia coli in milk using compressed carbon dioxide as inactivating agent

Low-carbon treatment and remediation of oil sludge in mid-to-high latitude regions: A coupled approach of freeze-thaw and supercritical CO2 extraction

The oil sludge produced while extracting large oil and gas fields in the middle and high latitude regions has caused serious pollution to the surrounding soil. The key to solving this problem in the future is to unify the remediation of soil and the treatment of oil sludge. This study uses supercritical carbon dioxide(scCO2) technology to construct a low-carbon method, providing a new approach to achieve this goal. The study determines the optimal extraction conditions for black calcareous soil with 15% oil content to be 55 °C, 25 MPa, and 90 min through single factor and response surface experiments. Experiments on the scCO2 extraction coupled with freeze-thaw cycles show that oil sludge with a water content of 10% can improve the extraction efficiency of scCO2 by about 2.69% after less than five freeze-thaw cycles. The study also compares the extraction efficiency of the four soils, with a difference of 6.03% observed under the same conditions. Additionally, we analyze the impact of the extraction process on changes in the properties of the oil and soil in the oil sludge. Comprehensive tests, including scanning electron microscope (SEM), nutrient detection, X-ray powder diffractometer (XRD), fourier transform infrared spectroscopy (FTIR), and Gas Chromatography (GC), have been conducted. Results show that standalone scCO2 extraction can remove up to 98.2% of petroleum hydrocarbons from the oil sludge, while simultaneously causing small changes to the soil microstructure and the crystal structure of the oil sludge. Furthermore, this process does not lead to a significant depletion of key nutrients or the generation of new pollutants.

Effect of supercritical carbon dioxide on protein structure modification and antimicrobial peptides production of Mongolian cheese and its in vitro digestion

The aim of this research was to investigate the effects of supercritical carbon dioxide (SC-CO2) treatment on protein structure in Mongolian cheese. The peptides during the digestive process of the SC-CO2 treated cheese were also studied. SC-CO2 technology was utilized to treat Mongolian cheese at three temperatures (45, 55 and 65 °C) and three pressures (7.5, 12.5 and 17.5 MPa). The results of fluorescence, ultraviolet-visible, Fourier transform infrared spectroscopy and free sulfhydryl groups showed that SC-CO2, particularly at 65 °C and 17.5 MPa, modified the protein structure in Mongolian cheese effectively. The data of LC-MS/MS-based peptidomics showed that the content of antimicrobial peptides found in the SC-CO2 treated Mongolian cheese was 1.55 times that of the untreated Mongolian cheese; the content of unique antimicrobial peptides in the digested SC-CO2 treated Mongolian cheese was 1.46 times that of the digested untreated Mongolian cheese, which proved that SC-CO2 could help produce antimicrobial peptides in cheese not only during the process of SC-CO2 treatment but during subsequent simulated gastrointestinal digestion as well. In conclusion, SC-CO2 could be considered a promising method to develop cheese products with potential health benefits.

Supercritical carbon dioxide technology in food processing: Insightful comprehension of the mechanisms of microbial inactivation and impacts on quality and safety aspects

Supercritical carbon dioxide (SC-CO2) has emerged as a nonthermal technology to guarantee food safety. This review addresses the potential of SC-CO2 technology in food preservation, discussing the microbial inactivation mechanisms and the impact on food products' quality parameters and bioactive compounds. Furthermore, the main advantages and gaps are denoted. SC-CO2 technology application causes adequate microbial reductions (>5 log cfu/mL) of spoilage and pathogenic microorganisms, enzyme inactivation, and improvements in the storage stability in fruit and vegetable products (mainly fruit juices), meat products, and dairy derivatives. SC-CO2-treated products maintain the physicochemical, technological, and sensory properties, bioactive compound concentrations, and biological activity (antioxidant and angiotensin-converting enzyme-inhibitory activities) similar to the untreated products. The optimization of processing parameters (temperature, pressure, CO2 volume, and processing times) is mandatory for achieving the desired results. Further studies should consider the expansion to different food matrices, shelf-life evaluation, bioaccessibility of bioactive compounds, and in vitro and in vivo studies to prove the benefits of using SC-CO2 technology. Moreover, the impact on sensory characteristics and, mainly, the consumer perception of SC-CO2-treated foods need to be elucidated. We highlight the opportunity for studies in postbiotic production. In conclusion, SC-CO2 technology may be used for microbial inactivation to ensure food safety without losing the quality parameters.

The Extraction and Impact of Essential Oils on Bioactive Films and Food Preservation, with Emphasis on Antioxidant and Antibacterial Activities-A Review

Essential oils, consisting of volatile compounds, are derived from various plant parts and possess antibacterial and antioxidant properties. Certain essential oils are utilized for medicinal purposes and can serve as natural preservatives in food products, replacing synthetic ones. This review describes how essential oils can promote the performance of bioactive films and preserve food through their antioxidant and antibacterial properties. Further, this article emphasizes the antibacterial efficacy of essential oil composite films for food preservation and analyzes their manufacturing processes. These films could be an attractive delivery strategy for improving phenolic stability in foods and the shelf-life of consumable food items. Moreover, this article presents an overview of current knowledge of the extraction of essential oils, their effects on bioactive films and food preservation, as well as the benefits and drawbacks of using them to preserve food products.

Effect of Green Food Processing Technology on the Enzyme Activity in Spelt Flour

In this research, a new approach to enzyme inactivation in flour was presented by supercritical technology, considered a sustainable technology with lower energy consumption compared to other technologies that use ultra-high temperature processing. Total protein concentration and the activity of enzymes α-amylase, lipase, peroxidase, polyphenol oxidase, and protease were determined in flour pre-treated with scCO₂. During the study, it was observed that the activity of enzymes such as lipase and polyphenol oxidase, was significantly reduced under certain conditions of scCO₂ treatment, while the enzymes α-amylase and protease show better stability. In particular, polyphenol oxidase was effectively inactivated below the 60% of preserved activity at 200 bar and 3 h, whereas α-amylase under the same conditions retained its activity. Additionally, the moisture content of the scCO₂-treated spelt flour was reduced by 5%, and the fat content was reduced by 58%, while the quality of scCO₂-treated flour was maintained. In this regard, the sustainable scCO₂ process could be a valuable tool for controlling the enzymatic activity of spelt flour since the use of scCO₂ technology has a positive effect on the quality of flour, which was verified by the baking performance of spelt flour with the baked spelt bread as an indicator of quality.

Determination of the Lethal Injury on the Inactivation of Saccharomyces pastorianus Cells by Low-pressure Carbon Dioxide Microbubbles

To clarify the lethal injury related to the inactivation of Saccharomyces pastorianus cells by low-pressure carbon dioxide microbubble (CO₂MB) treatment, surviving number, leakage of nucleic acids and proteins, fluorescence polarisation (FP) of the cell membrane, activity of alkaline phosphatase (AP), intracellular pH (pH_in), mitochondrial membrane potential (MMP), cell surface hydrophobicity (CSH) and oxidative stress of S. pastorianus treated with CO₂MB at various temperatures were measured. The number of surviving S. pastorianus cells decreased below the detection limit after CO₂MB treatment at temperatures of 40, 45 and 50 ℃, inducing a 2-log reduction at 35 ℃. The S. pastorianus cells treated with CO₂MB at temperatures above 40 ℃ showed an increase in FP and leakage of nucleic acids and proteins. The AP in S. pastorianus cells treated with CO₂MB at a temperature of 35 ℃ was also activated but inactivated at temperatures above 40 ℃. Furthermore, the decrease in pH_in and MMP and the increase in CSH of S. pastorianus were caused by CO₂MB treatment at temperatures above 35 ℃. Oxidative stress in S. pastorianus cells was also increased by CO₂MB treatment without warming but decreased at temperatures above 35 ℃. Our results lead us to infer that the type of cell injury in S. pastorianus induced by CO₂MB treatment differed from that caused by the treatment temperature and that the lethal injury was enzyme inactivation.

S. M. Montenegro MC, Rodríguez-Díaz JM. Contaminants in the cow's milk we consume? Pasteurization and other technologies in the elimination of contaminants

Cow's milk is currently the most consumed product worldwide. However, due to various direct and indirect contamination sources, different chemical and microbiological contaminants have been found in cow's milk. This review details the main contaminants found in cow's milk, referring to the sources of contamination and their impact on human health. A comparative approach highlights the poor efficacy and effects of the pasteurization process with other methods used in the treatment of cow's milk. Despite pasteurization and related techniques being the most widely applied to date, they have not demonstrated efficacy in eliminating contaminants. New technologies have appeared as alternative treatments to pasteurization. However, in addition to causing physicochemical changes in the raw material, their efficacy is not total in eliminating chemical contaminants, suggesting the need for new research to find a solution that contributes to improving food safety.

Combination of supercritical CO2 and high-power ultrasound for the inactivation of fungal and bacterial spores in lipid emulsions

For the first time, this study addresses the intensification of supercritical carbon dioxide (SC-CO2) treatments using high-power ultrasound (HPU) for the inactivation of fungal (Aspergillus niger) and bacterial (Clostridium butyricum) spores in oil-in-water emulsions. The inactivation kinetics were analyzed at different pressures (100, 350 and 550 bar) and temperatures (50, 60, 70, 80, 85 °C), depending on the microorganism, and compared to the conventional thermal treatment. The inactivation kinetics were satisfactorily described using the Weibull model. Experimental results showed that SC-CO2 enhanced the inactivation level of both spores when compared to thermal treatments. Bacterial spores (C.butyricum) were found to be more resistant to SC-CO2 + HPU, than fungal (A.niger) ones, as also observed in the thermal and SC-CO2 treatments. The application of HPU intensified the SC-CO2 inactivation of C.butyricum spores, e.g. shortening the total inactivation time from 10 to 3 min at 85 °C. However, HPU did not affect the SC-CO2 inactivation of A.niger spores. The study into the effect of a combined SC-CO2 + HPU treatment has to be necessarily extended to other fungal and bacterial spores, and future studies should elucidate the impact of HPU application on the emulsion's stability.

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.

Effect of supercritical carbon dioxide processing on Vibrio parahaemolyticus in nutrient broth and in oysters (Crassostrea gigas)

This study aimed to evaluate the technical feasibility of supercritical carbon dioxide (sc-CO₂) treatment for Vibrio parahaemolyticus inactivation in oysters (Crassostrea gigas) and in nutrient broth. For this purpose, a variable-volume reactor was used as experimental system and a 2³ factorial design was adopted considering the mass ratio between carbon dioxide and the product, pressurization and depressurization rate and pressurization cycles. Through statistical analysis of the experimental data, the mass ratio of 1:0.8 (product:carbon dioxide), depressurization rate of 10.0 MPa/min and one cycle of pressurization was determined as the best process condition to eliminate V. parahaemolyticus, and this was the condition used for the inactivation kinetic analysis. Comparison between the inactivation kinetics of V. parahaemolyticus showed that the behavior of this microorganism inactivation depends on the environment in which it operates and its initial count. The results confirm that the supercritical carbon dioxide is effective in inactivating microorganisms in oysters, including pathogenic V. parahaemolyticus, demonstrating the potential of this technology in the food industry.

Whey-grape juice drink processed by supercritical carbon dioxide technology: Physicochemical characteristics, bioactive compounds and volatile profile

The effect of supercritical carbon dioxide technology (SCCD, 14, 16, and 18MPa at 35±2°C for 10min) on whey-grape juice drink characteristics was investigated. Physicochemical characterization (pH, titratable acidity, total soluble solids), bioactive compounds (phenolic compounds, anthocyanin, DPPH and ACE activity) and the volatile compounds were performed. Absence of differences were found among treatments for pH, titratable acidity, soluble solids, total anthocyanin and DPPH activity (p-value>0.05). A direct relationship between SCCD pressure and ACE inhibitory activity was observed, with 34.63, 38.75, and 44.31% (14, 16, and 18MPa, respectively). Regards the volatile compounds, it was noted few differences except by the presence of ketones. The findings confirm the SCCD processing as a potential promising technology to the conventional thermal treatment.

Use of Non-Conventional Cell Disruption Method for Extraction of Proteins from Black Yeasts

The influence of pressure and treatment time on cells disruption of different black yeasts and on activities of extracted proteins using supercritical carbon dioxide process was studied. The cells of three different black yeasts Phaeotheca triangularis, Trimatostroma salinum, and Wallemia ichthyophaga were exposed to supercritical carbon dioxide (SC CO₂) by varying pressure at fixed temperature (35°C). The black yeasts cell walls were disrupted, and the content of the cells was spilled into the liquid medium. The impact of SC CO₂ conditions on secretion of enzymes and proteins from black yeast cells suspension was studied. The residual activity of the enzymes cellulase, β-glucosidase, α-amylase, and protease was studied by enzymatic assay. The viability of black yeast cells was determined by measuring the optical density of the cell suspension at 600 nm. The total protein concentration in the suspension was determined on UV–Vis spectrophotometer at 595 nm. The release of intracellular and extracellular products from black yeast cells was achieved. Also, the observation by an environmental scanning electron microscopy shows major morphological changes with SC CO₂-treated cells. The advantages of the proposed method are in a simple use, which is also possible for heat-sensitive materials on one hand and on the other hand integration of the extraction of enzymes and their use in biocatalytical reactions.