Search

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.

The presence of tens of Clostridium botulinum spores per gram of honey can cause infantile botulism. Thermal treatment is insufficient to inactivate these resistant forms. This study explored the effectiveness of supercritical CO2 (scCO2) on its own and combined with lemon (LEO), clove (CLEO), and cinnamon (CEO) essential oils on the inactivation of Clostridium sporogenes (CECT 553) as a surrogate of Clostridium botulinum. In water, the degree of inactivation at 10 MPa after 60 min increased with the increasing temperature, reducing the population by 90% at 40 °C and by 99.7% at 80 °C. In contrast, when applied to honey, scCO2 did not inactivate Clostridium spores satisfactorily at temperatures below 70 °C, which was related to the protective effect of honey. Meanwhile, scCO2 modified with CEO (

High-pressure carbon dioxide (HPCD), a novel non-thermal pasteurization technology, has attracted the attention of scientists due to its high pasteurization efficiency at a lower temperature and pressure. However, the inactivation mechanism has not been well researched, and this has hindered its commercial application. In this work, we used a sub-lethal HPCD condition (4.0 MPa, 30 °C) and a recovery condition (30 °C) to repair the damaged cells. Transcriptome analysis was performed by using RNA sequencing and gene ontology analysis to investigate the detailed lethal mechanism caused by HPCD treatment. RT-qPCR analysis was conducted for certain upregulated genes, and the influence of HPCD on protoplasts and single-gene deletion strains was investigated. Six major categories of upregulated genes were identified, including genes associated with the pentose phosphate pathway (oxidative phase), cell wall organization or biogenesis, glutathione metabolism, protein refolding, phosphatidylcholine biosynthesis, and AdoMet synthesis, which are all considered to be associated with cell death induced by HPCD. The inactivation or structure alteration of YNL194Cp in the organelle membrane is considered the critical reason for cell death. We believe this work contributes to elucidating the cell-death mechanism and providing a direction for further research on non-thermal HPCD sterilization technology.

In this study, the changes in enzyme activities, total polyphenols, phenolic profile, and physicochemical properties from thermally (25&ndash, 75 &deg, C) and high-pressure carbon dioxide (HP-CO2) (25&ndash, 65 &deg, C/20 MPa)-treated apple juice were investigated. The HP-CO2 exhibited complete inactivation of polyphenol oxidase (PPO) at 65 &deg, C, whereas PPO was still active at 75 &deg, C under thermal processing (TP). Similarly, the relative activity of peroxidase (POD) significantly decreased by 71% at 65 &deg, C under HP-CO2 processing, whereas TP was less effective. HP-CO2 and TP treatments at 65 &deg, C reduced the browning degree (BD) value to 0.47 and 0.89, respectively. Thus, HP-CO2 inhibits the browning reactions caused by PPO and POD enzymes at each operating temperature. The concentration of epicatechin and catechin increased significantly with increasing temperature above 45 &deg, C in TP-treated juices. HP-CO2 treatment increased the same phenolic compounds at 35 &deg, C and 9 MPa, whereas high-temperature and -pressure conditions caused insignificant changes in concentration of epicatechin and catechin. Changes in others phenolic compounds were insignificant under TP and HP-CO2 treatment. Overall, HP-CO2 is a promising technology to get high-quality juices with lower enzyme activity.

El presente estudio se orientó a investigar el efecto de la utilización de dióxido de carbono de alta presión en la inactivación de bacterias aerobias mesófilas y Escherichia coli ATCC 25922 previamente inoculadas en leche humana. Durante el proceso se analizaron las siguientes variables: ratio entre la masa de muestra y el CO2 (1:0,2; 1:0,6 y 1:1 m/m); tasa de despresurización (1, 5,5 y 10 MPa/min) y ciclo de presión (1, 3 y 5). La disminución más pronunciada de bacterias aerobias mesófilas y de E. coli (>6,0 y >5,0 log, respectivamente) se logró empleando una ratio de 1:1, una tasa de despresurización de 10 MPa/min y un solo ciclo de presurización/despresurización. Se comprobó que la tasa de despresurización constituye una variable importante para el proceso de inactivación. En este sentido, los resultados permiten constatar que puede aplicarse dióxido de carbono de alta presión a la leche materna como alternativa segura a la pasteurización utilizada en los bancos de leche humana. The effect of high-pressure carbon dioxide processing on inactivation of aerobic mesophilic bacteria and Escherichia coli ATCC 25922 inoculated in human milk was investigated. The effect of the ratio between sample mass and CO2 (1:0.2; 1:0.6 and 1:1 m/m); depressurization rate (1, 5.5 and 10 MPa/min); and pressure cycling (1, 3 and 5) were the process variables studied. The best reductions in aerobic mesophilic bacteria as well as in E. coli (>6.0 and >5.0 log, respectively) were obtained with a ratio of 1:1, a depressurization rate of 10 MPa/min, and one cycle of pressurization/depressurization. The depressurization rate was found to be an important variable in the inactivation process. The results suggest that high-pressure carbon dioxide processing can be applied to human milk as a safe alternative to the pasteurization employed in human milk banks.

Fresh fruit juices consumption has greatly risen over the last years, due to the increasing demand for fresh-like foods. Microbial growth and enzymatic activity as well as physical and chemical changes can contribute to quality depletion of these juices. High-pressure carbon dioxide (HPCD) is a promising nonthermal technology for the stabilization of fresh juices. During the treatment, juice is in contact with carbon dioxide at temperature-pressure conditions approaching the critical point. HPCD pressures rarely exceed 50 MPa. Temperature is generally between 20°C and 50°C, low enough to maintain the product fresh-likelihood. This chapter reviews the effects of HPCD treatment on liquid food, with particular focus on fruit juices. To this aim, a description of the basic principles of this technology and of its effects on microorganisms, enzymes and sensory, physicochemical, and physical properties of fruit juices is presented. Finally the description of combined strategies and plants nowadays available for HPCD treatment is reported.

A combined treatment based on high-pressure carbon dioxide and high-power ultrasound (HPCD + HPU) technologies was investigated for the pasteurization of fresh-cut coconut. Inactivation kinetics of both the natural microbiota and Salmonella enterica typhimurium spiked on the product were determined at 12 MPa and 10 W, delivered every 2 min of treatment, as a function of temperature (from 24 to 50 °C) and treatment time (from 5 up to 30 min). Additionally, to study the effect of HPCD + HPU on the quality of the product, physicochemical attributes (total acidity, pH, color, texture, dry matter, fat content, enzymatic activity, antioxidant capacity, phenols, flavonoids, and phenolic acids) were measured after the combined treatment and during a refrigerated shelf life of 4 weeks. The results revealed that HPCD + HPU increased microbial inactivation rates compared with HPCD alone: 8 log reductions of S. typhimurium were achieved with HPCD + HPU at 12 MPa, 40 °C, 20 min, while just a 4 log reduction was achieved with HPCD alone. Similar results were obtained for the natural microbiota; milder conditions of temperature and pressure were sufficient to assure inactivation to undetectable levels even of mesophilic microorganisms, the most resistant ones. Total acidity and pH did not change after the combined treatment and during the entire storage of 4 weeks, while slight differences were observed for the other physicochemical parameters. Overall, the results showed the feasibility and the potential of HPCD + HPU as an innovative non-thermal technology for the pasteurization of fresh-cut fruits.

Coconut water is a tropical beverage with a distinctive odor and flavor that has until now not been adequately characterized. In the present paper, the volatile compound composition of coconut water was investigated using head space solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). Analyses were made of fresh untreated (FU) samples and samples pasteurized using two different technologies: conventional thermal treatment (thermal pasteurization (TP)) and high-pressure carbon dioxide (HPCD) pasteurization, which has recently attracted great interest as an innovative nonthermal preservation treatment. Seventy-three volatile compounds were identified; 27 of them reported for the first time in coconut water. The results showed that HPCD treatment depletes short- and medium-chain alcohols, while TP treatment triggers an increase in aldehydes, ketones, and 2-acetyl-1-pyrroline, an aroma compound active at low odor thresholds and characterized by “popcorn” and “toasted” odor descriptors. Sensory discrimination analysis (triangle test) showed there to be no significant differences between HPCD and FU samples, while TP and FU samples were perceived significantly differently. Descriptive sensory analyses evidenced more intense “cooked,” “toasted bread,” and “hazelnut” characteristics in TP-treated coconut water, consistent with HS-SPME-GC-MS data. In conclusion, instrumentally measurable changes in volatile compounds were more moderate with HPCD than with TP treatment and were not sensorially perceivable compared with the FU product.

Investigation of cost effective CO 2 adsorbent has been a long demanding task in the present scenario of global warming. The present work investigates the high pressure carbon dioxide capture capacity of low cost magnetite decorated functionalized graphite nanoplatelets novel nanocomposite. Graphite nanoplatelets were prepared by acid intercalation followed by thermal exfoliation. Functionalization of graphite nanoplatelets was done by treatment in acidic medium. Magnetite nanoparticles were decorated onto functionalized graphite nanoplatelets surface by a chemical method. Magnetite decorated functionalized graphite nanoplatelets nanocomposite was characterized by electron microscopy, X-ray powder diffraction pattern, surface area analysis, Raman spectroscopy and FTIR spectroscopy techniques. The carbon dioxide capture capacity was measured using high pressure Sieverts apparatus. Adsorption capacity was calculated using the gas equation and incorporating van der Waals corrections at three different temperatures (25, 50 and 100 �C). A large enhancement in carbon dioxide uptake capacity of 55%, 80%, and 90% at near 11.5 bar pressure for 100 �C, 50 �C and 25 �C, respectively, was achieved by decorating magnetite nanoparticles onto functionalized graphite nanoplatelet surface. � 2011 The Royal Society of Chemistry.