Carbon Dioxide-enriched Atmospheres Research Articles

Changes in the bioactive properties of strawberries caused by the storage in oxygen- and carbon dioxide-enriched atmospheres.

The changes in the antioxidant capacity, anti‐inflammatory, and wound healing properties of strawberry fruits as a consequence of the storage in atmospheres enriched in oxygen and carbon dioxide were investigated. Berries were exposed to two different gas compositions: 70% O2 + 20% CO2 and 90% O2 + 10% CO2, and stored for up to 20 days at 5°C. The antioxidant capacity, assessed through DPPH and FRAP methods, decreased around 17% in samples exposed to 70% O2 + 20% CO2 at day 20. However, the antioxidant activity of fruits stored in 90% O2 + 10% CO2 was maintained until day 20 and experienced an increase of around 10% on day 10. Moreover, strawberry stored in 90% O2 + 10% CO2 at days 5–10 showed an improved suppression of the pro‐inflammatory genes Cox‐2 and iNOS up to 30% higher than samples at day 0 in an in vitro LPS‐stimulated RAW 264.7 macrophage culture. In addition, berries exposed to 90% O2 + 10% CO2 at day 10 showed a human dermal fibroblast migration 30% higher than samples at day 0 in an in vitro skin‐fibroblast‐migration model. Therefore, evidence suggests that strawberry storage in 90% O2 + 10% CO2 can be a promissory alternative to offer fruits with enhanced bioactivity.

Co-firing coal with biomass in oxygen- and carbon dioxide-enriched atmospheres for CCS applications

Biomass combustion and carbon capture and storage (CCS) individually represent significant options for decarbonising the power generation sector and when combined may permit a carbon–neutral or even carbon-negative process. Despite this potential, little research has been published that examines the combustion of biomass in atmospheres with application in CCS processes. This work reports on bench- and laboratory-scale testing of biomass and coal combustion in atmospheres enriched in O2 and CO2 which are relevant for retrofitting power stations for oxyfuel combustion. At bench-scale, thermogravimetric analysis shows substituting N2 as the combustion diluent with CO2 has little impact on the combustion properties of the fuels but that increasing the O2 concentration accelerates combustion of coal and biomass chars. Results from cofiring three biomasses with coal at 20kW scale suggest substitution of N2 with CO2 significantly reduces temperatures, carbon burnout and emissions of NO while combustion in O2-enriched conditions has the opposite effects. Emissions of NO and SO2 were found to reduce compared to air in combustion atmospheres enriched with O2 and CO2 while combustion temperatures and carbon burnout slightly increased.

PHYSIOLOGY OF CA TREATED PRODUCE

Storage of fresh horticultural perishables within the optimum range of low oxygen and/or elevated carbon dioxide atmospheres for each commodity reduces their respiration and ethylene production rates. However, outside this range respiration and ethylene production rates can be stimulated indicating a stress response, which can contribute to incidence of physiological disorders and increased susceptibility to decay. Exposure to 30-80 kPa oxygen atmospheres stimulates respiration and ethylene production and action in some commodities. Carbon dioxide-enriched atmospheres inhibit activity of ACC synthase, while ACC oxidase activity is stimulated by low carbon dioxide and inhibited at high carbon dioxide and/or low oxygen concentrations. Ethylene action is inhibited by elevated carbon dioxide atmospheres. Optimum CA retard loss of chlorophyll, biosynthesis of carotenoids and anthocyanins, and biosynthesis and oxidation of phenolic compounds. CA reduce the activity of cell wall degrading enzymes that cause fruit softening and enzymes involved in lignification leading to toughening of vegetables. CA influence flavor quality by reducing loss of acidity, starch to sugar conversion, and biosynthesis of aroma volatiles, especially esters. Retention of ascorbic acid and other vitamins results in better nutritional quality, including antioxidant activity, of fruits and vegetables when kept in their optimum CA.

Carbon dioxide-enriched atmospheres during cold storage limit losses from Botrytis but accelerate rachis browning of ‘Redglobe’ table grapes

We evaluated a range of CO2 and O2 concentrations as a potential substitute to SO2 treatments for controlling decay development on ‘Redglobe’ table grape during storage. During the 1998 season, early (14% soluble solids concentration, SSC) and late harvested (17% SSC) ‘Redglobe’ grapes were stored in 16 controlled atmospheres of 5, 10, 15, 20, and 25 kPa CO2 combined with 3, 6, and 12 kPa O2. During the 1999 season, 10 or 15 kPa CO2 combined with 3, 6, and 12 kPa O2 were tested in comparison with air stored grapes as control. In the 2000 season, late harvested ‘Redglobe’ grapes were kept in 12 kPa CO2+6 kPa O2 in comparison with standard commercial storage practices of SO2 fumigation. None of the atmospheres tested for up to 12 weeks at 0 °C influenced SSC, titratable acidity (TA), SSC:TA, or berry shatter and browning. Rachis browning was accelerated and trained judges perceived ‘off-flavor’ in grapes exposed to CO2 levels above 10 and 15 kPa for early and late harvested ‘Redglobe’ grapes, respectively. Atmospheres including above 10 kPa CO2 controlled decay incidence and spread among berries (nesting) independent of O2 concentrations during storage at 1 °C for up to 8 weeks and after 3 days at 20 °C, simulating a retail display period. Based on these data, a combination of 10 kPa CO2 with 3, 6 or 12 kPa O2 is suggested for up to 12 weeks storage for late harvested ‘Redglobe’ grapes. An atmosphere of 10 kPa CO2+6 kPa O2 is suggested for early harvested ‘Redglobe’ grapes, but not to exceed 4 weeks.

Changes in Strawberry Anthocyanins and Other Polyphenols in Response to Carbon Dioxide Treatments

Carbon dioxide-enriched atmospheres are used to reduce the incidence and severity of decay and to extend the postharvest life of strawberries. The influence of CO2 on the postharvest quality parameters of strawberries, particularly the stability of anthocyanins and other phenolic compounds, was investigated. Freshly harvested strawberries were placed in jars ventilated continuously with air or air enriched with 10%, 20%, or 40% CO2 at 5 °C for 10 days. Samples were taken initially, and after 5 and 10 days of storage, and color (L* a* b* color space), pH, TA, TSS, and firmness were measured. Anthocyanins and other phenolics were analyzed by HPLC. Elevated CO2 degraded internal color while air-treated fruit remained red. Internal and external tissues differed in composition and concentration of phenolic compounds. CO2 had a minimal effect on the anthocyanin content of external tissues but induced a remarkable decrease in anthocyanin content of internal tissues. Factors, such as pH and copigmentation, that could explain this degradation are discussed. Keywords: Fragaria × ananassa; controlled atmosphere; quality parameters; anthocyanins; phenolics

Effect of Carbon Dioxide on Stability of Anthocyanins and Other Phenolic Compounds during Storage of Fresh Strawberries

Carbon dioxide-enriched atmospheres are used to reduce decay incidence and severity and extend the postharvest life of strawberries. However, depending on the cultivar, carbon dioxide concentrations of ≥20% can be detrimental to color (change from red to purple) and flavor (development of off-flavors). Our objective was to determine the effect of elevated carbon dioxide levels on the stability of the anthocyanins and other phenolic compounds to examine their role in color changes of strawberries. Freshly harvested strawberries were placed in jars ventilated continuously with air or air enriched with 10%, 20% or 40% carbon dioxide at 5°C for 10 days. Anthocyanins and other phenolics were extracted at 0, 5, and 10 days from homogenized samples. The samples were purified using Sep-pac C18 cartridges. The purified methanolic extract was injected directly into HPLC coupled to a photodiode array detector. Cyanidin-3-glucoside, pelargonidin-3-glucoside, and pelargonidin-3-rutinoside were identified as the major anthocyanins. After 5 and 10 days in storage there was a reduction in the total amount of anthocyanins. This degradation was lower in air than in carbon dioxide-treated strawberries, but the anthocyanin profile remained the same. Flavonols (e.g., quercetin and kaempferol derivatives) and phenolic acids (e.g., ellagic acid) decreased during storage, and this decrease was exacerbated by elevated carbon dioxide atmospheres. Carbon dioxide-induced changes in the quantities of the previously listed anthocyanins and phenolic compounds may be the cause of color changes from red to purple in strawberries.

373 MITOCHONDRIAL RESPIRATlON OF `HASS' AVOCADOS IN RESPONSE TO ELEVATED CO, CONCENTRATIONS

Carbon dioxide-enriched atmospheres can be effective in the retardation of ripening and in the reduction of decay of horticultural commodities. However, concentrations in excess of the tolerance level may cause physiological damage. The goal of our research is to elucidate the specific regulatory mechanisms of CO2 actions. Cytochrome oxidase (CytOx) in vitro activity in preclimacteric avocado fruit stored in air or 40% CO2 + 12.6% O2 was evaluated at 20C. Activities were determined during treatment and also after a transfer to air. Fruit treated with 40% CO2 + 12.6% O2 had elevated CytOx in vitro activity when compared to air-stored fruit. Immunoblot analysis was performed to determine if the increase in CytOx activity could be due to an increase in enzyme concentration. The decline in respiration rate of CO,-treated fruit was most likely due to the decrease in intracellular pH and its effect on the activities of important respiratory enzymes, including CytOx. The regulatory mechanisms of other mitochondrial respiratory enzymes in `Hass' avocados exposed to elevated CO2 atmospheres are also under investigation.

Effect of Carbon Dioxide and Oxygen Enriched Atmospheres on the Shelf-Life of Refrigerated Pork Packed in Plastic Bags

Changes in bacterial numbers, metmyoglobin percentage and 2-thiobarbituric acid number during the chill storage of pork longissimus dorsi packed with air, carbon dioxide, carbon dioxide and oxygen or vacuum-packed in plastic bags of high (polyethylene) and low (Cryovac BB-1) permeability to gases were studied. The fast increase of viable counts in polyethylene bags showed that plastic films of high permeability are not suitable to extend the shelf-life of meat using modified atmospheres. In Cryovac bags both carbon dioxide-enriched atmospheres and vacuum-packaging inhibited aerobic organisms, keeping the bacterial flora (mainly lactobacilli and Brochothrix thermosphacta) below the level of 108/cm2 for about 3 weeks. Metmyoglobin formation was not affected by 20% carbon dioxide, whilst 80% oxygen significantly decreased its rate. Metmyoglobin accumulation in vacuum-packed samples was even slower than in the oxygen-enriched atmosphere, but meat color was less attractive in the former than in the latter. Lipid oxidation was not the limiting factor of shelf-life in either of these two atmospheres. Off-odors appeared in both at approximately 20–22 d of storage.

Control of Postharvest Decays of Blueberries by Carbon Dioxide-Enriched Atmospheres

Effet du maintien des airelles en atmosphere de CO 2 pour le transport a longue distance sur la qualite des fruits et sur les maladies de conservation

Effect of oxygen- and carbon dioxide-enriched atmospheres on shelf-life extension of refrigerated ground pork

The oxidation of the lipids and myoglobin of ground pork meat stored in oxygen- and carbon dioxide-enriched atmospheres at 1 °C has been studied. Elevated oxygen levels (80–100%) depressed myoglobin oxidation, increasing the time to 50% metmyoglobin formation from four to about thirteen days. Twenty per cent carbon dioxide greatly reduced the rate of lipid oxidation, extending the time to reach a TBA number of 5 from five to about twelve days. Tocopherol and ascorbic acids were efficient inhibitors of lipid oxidation but citric acid was not.

Lipid and myoglobin oxidation in pork stored in oxygen- and carbon dioxide-enriched atmospheres

The formation of malonaldehyde and metmyoglobin in pork muscles stored in oxygen- and carbon dioxide-enriched atmospheres at 1°C was followed. The formation of metmyoglobin at the surface of the muscles was independent of carbon dioxide concentration. However, increased oxygen concentration caused a significant decrease in the rate of metmyoglobin formation; the surface concentration of metmyoglobin was below 30% even after 15 days' storage in 80% oxygen/20% carbon dioxide. Lipid oxidation, as measured by malonaldehyde production (TBA Number), occurred at the same rate in air an mixtures containing 80, 90 and 100% oxygen. In some muscles, the rate was such that rancidity was apparent within 6 days at 1°C and, for pork, lipid oxidation, and not bacterial spoilage or metmyyoglobin formation, may be the limiting factor in the use of oxygen-containing atmospheres for storage.