COLOR IMPROVEMENT OF KOSHER BEEF USING SODIUM ASCORBATE AND ERYTHORBATE

The koshering process involves soaking meat in water followed by massive surface salting and rinsing to remove the salt. This process causes undesirable discoloration during storage at 4C, as compared to nonkosher beef (P<0.01). Beef steaks were dipped into sodium ascorbate (SA) or erythorbate (SE) solutions for various time periods. Untreated steaks, from the same cut, served as controls. All samples were packaged into modified atmospheres of 65% O₂ and 35% CO₂. The color of sample was observed periodically during illuminated storage at 4C. The typical red color was maintained at 4C for up to 21 days when the meat was dipped for 1 min in a 2 or 4% SE solution (pH 6.5), packaged in 65% O₂ and 35% CO₂, while the controls showed severe discoloration after 2 to 3 days. The treatment with SE had also a positive effect in reducing initial total microbial counts by 1.5 log CFU/g.     

Physicochemical, Microbiological, and Sensory Evaluation of Minimally Processed Tarocco Clone Oranges Packaged with 3 Different Permeability Films

ABSTRACT: Fruits of 3 Tarocco clones ('Gallo', 'Arcimusa', and 'Scirè') were sliced, packaged with different permeability films, and stored at 4°C for 14 to 15 d to find the best clone for processing and the most suitable packaging conditions to extend the shelf life of these products. Physicochemical parameters of Tarocco oranges slices, packaged with 3 films of different permeability, did not show marked decay phenomena during the storage days. Only a reduction in the ascorbic acid content was observed in almost all the examined clones, especially in products packaged with the most O₂ permeable films. Concerning microbiological contamination, all clones, packaged with the 3 films, showed, until the 12th storage day, a lower number of colony forming units (CFU)/g (≤ 3.6 × 10⁷ CFU/g) for mesophilic viable counts than the 2 microbiological criteria generally used for fresh-cut fruit and vegetables (10⁸ CFU/g for mesophilic viable counts). In fact, for these products it is possible to expect a shelf life longer than 12 to 13 d. Regarding sensory results, it was observed that the minimally processed Tarocco clone slices packaged with the most permeable to O₂ film were the most appreciated.     

Influence of Gaseous Atmosphere on Morphology and Cellular Fatty Acid Composition of Campylobacter jejuni

ABSTRACT: We evaluated the effect of growth environment on morphology and fatty acid (FA) profiles of 2 strains of C ampylobacter jejuni (ATCC 29428 and 33560) grown under various gaseous conditions. Viable counts were determined by plate count and percentages of coccoid cells. FA profiles were measured by gas chromatography. Plate counts were lowest when cultures were grown in air and highest in CO₂ (10%), O₂ (5%), and N₂ (85%). For 29428, percentages of coccoid cells did not differ among treatments. For 33560, percentages of coccoid cells were greater than for 29428 and varied among treatments (13% to 87%). There were no significant ( P > 0.05) relationships between percentages of coccoid cells and amounts of individual or combinations of FA either between or within strains.     

Decontamination Efficacy of Combined Chlorine Dioxide with Ultrasonication on Apples and Lettuce

ABSTRACT:  The bacterial reduction of Salmonella and Escherichia coli O157:H7-inoculated apples and lettuce by ClO₂ at 0, 5, 10, 20, and 40 ppm with and without 170-kHz ultrasonic treatments for 3, 6, and 10 min, respectively, have been studied. The treatments of ClO₂ at 20 and 40 ppm for 3, 6, and 10 min or at 5 and 10 ppm for 6 and 10 min with 170-kHz ultrasonication caused 3.115 to 4.253 log reductions in Salmonella and 2.235 to 3.865 log reduction in E. coli O157:H7 on inoculated apples. Using combined ClO₂ and ultrasonication to treat 4.48 × 10⁴ CFU/g Salmonella and 1.07 × 10⁵ CFU/g E. coli O157:H7-inoculated lettuce, the bacterial reductions were 2.257 to 2.972 and 1.357 to 2.264 log, respectively. The residual ClO₂ decreased with increasing treatment times, over 80% of ClO₂ was detected after the 3-min treatment, and more than 70% remained after the 10-min treatment time. No bacteria were recovered from the posttreatment solutions of ClO₂ or ClO₂ combined with ultrasonication. The temperature of the ClO₂ treatment was 20.1 °C, and it increased to 40.1, 44.9, and 50.3 °C, with 170-kHz ultrasonic treatments for 3, 6, and 10 min, respectively, on apples.     

Sensory Evaluation of Ground Beef Stored in High-oxygen Modified Atmosphere Packaging

ABSTRACT: The quality of ground beef stored in high-oxygen modified atmosphere packaging (MAP) (80% O₂ and 20% CO₂) was evaluated and compared to controls stored in oxygen-impermeable chubs. Patties were formed from the stored ground meat at d 1, 6, and 10. Color, microbial load, thiobarbituric acid (TBA) number, and sensory acceptability were measured. Patties from both treatments bloomed to red with a* values > 16. Aerobic plate counts increased to 9 × 10⁵CFU/gby 10 d storage, but were not different (p < 0.05) between treatments. TBA number of high-oxygen samples increased to 2.1 after 10 d, compared to 0.8 for controls. The flavor of samples in high-oxygen were rated less desirable after 6 or 10 d.     

Effects of Low-dose Gamma Irradiation on the Shelf Life and Quality Characteristics of Cut Romaine Lettuce Packaged under Modified Atmosphere

Cut romaine lettuce, packaged under modified atmosphere, was subjected to 0.15 and 0.35 kGy gamma irradiation. Irradiation at 0.35 kGy decreased aerobic plate counts by 1.5 logs and yeast and mold counts by 1 log; these differences were maintained through the 22-d storage. Irradiation at 0.15 kGy caused smaller reductions in microbial counts. A decrease in headspace CO₂ was observed in the 0.35-kGy-treated lettuce, although CO₂ concentrations increased in all samples with storage. O₂ concentration was not affected by irradiation. Ten percent loss in firmness was observed at 0.35 kGy, while other sensory attributes such as color, generation of off-flavor, and appearance of visual defects were not affected.     

MODELING FREQUENCY DISTRIBUTION of STEADY-STATE O2 PARTIAL PRESSURES IN MODIFIED-ATMOSPHERE PACKAGES

A mathematical model was developed to predict the frequency distribution of steady-state O₂ partial pressures in modified-atmosphere packages of fresh and minimally processed fruits and vegetables. Variation in O₂ uptake was predicted to have relatively larger influence on the package O₂ distribution than variation in film permeability to O₂. the model also predicted that the range of O₂ partial pressures in the packages would be larger for the products with lower K_1/2 (a constant in product O₂ uptake equation) values. the percent deviation of package O₂ partial pressures from [O₂]_med increased with [O₂]_med up to about 3 kPa and gradually decreased thereafter. Package O₂ distribution was symmetrical at higher [O₂]_med but became gradually asymmetrical with decreasing [O₂]_med from 6 kPa. the model was used to predict target [O₂]_med for the design of modified-atmosphere packages for different probability levels of having package O₂ being equal to or less than a minimum tolerable level of the product.     

Controlled atmosphere storage to decrease physiological disorders in nectarines

'Fantasia', 'Flavortop', and 'Flamekist' nectarines were examined for their response to controlled atmosphere (CA) storage. All three cultivars stored well for up to 6 weeks at 0°C in an atmosphere of 10% O₂+ 10% CO₂, while some but not all the cultivars also stored well in 2% O₂+ 5% CO₂ or 10% O₂+ 5% CO₂. The physiological storage disorders of internal breakdown and reddening were almost completely absent in nectarines kept in 10% O₂+ 10% CO₂. When 'Flamekist' nectarines from two harvests were stored in 10% O₂+ 10% CO₂ atmosphere for 6 or 8 weeks at 0°C, the fruit from the first harvest was of better quality after post-storage ripening. Although this controlled atmosphere prevented internal breakdown and reddening, after extended storage fruit did not develop the increased soluble solids content or extractable juice during post-storage ripening that occurred in non-stored fruit. Therefore, while preventing storage disorders, CA does not reduce the loss of ripening ability occurring during nectarine storage.     

Decontamination of Escherichia coli O157:H7 and Salmonella enterica on blueberries using ozone and pulsed UV-light

ABSTRACT:  Efficacy of gaseous ozone, aqueous ozone, and pulsed UV-light was evaluated for the purpose of decontaminating blueberries artificially contaminated with either Escherichia coli O157:H7 or Salmonella. Blueberries were exposed to 4 different gaseous ozone treatments: continuous ozone exposure, pressurized ozone exposure, and 2 combined treatments. Maximum reductions of Salmonella and E. coli O157:H7 after 64-min pressurized or 64-min continuous exposure were 3.0 and 2.2 log₁₀ CFU/g, respectively. Aqueous ozone experiments were conducted at 20 °C and 4 °C and zero plate counts were observed for E. coli O157:H7 and Salmonella after 64 min of ozone exposure at 20 °C. Finally, pulsed UV-light was evaluated at 3 different distances from the light. Maximum reductions of 4.3 and 2.9 log₁₀ CFU/g were observed at 8 cm from the light after 60 s of treatment for Salmonella and E. coli O157:H7, respectively. A sensory analysis as well as color analysis was performed on blueberries from each treatment agent; neither analysis detected a difference between treated and untreated blueberries. The results presented in this study indicate that ozone and pulsed UV-light are good candidates for decontamination of blueberries.     

Effects of gas atmosphere and temperature on the respiration rates of whole and sliced mushrooms (Agaricus bisporus)--implications for film permeability in modified atmosphere packages

ABSTRACT:  An open flowthrough respirometer was used to determine the respiration rates of whole and sliced mushrooms as a function of O₂, CO₂, and storage temperature. Respiration rates were measured under the following O₂ concentrations: 20, 15, 10, 5, and 2% at 5 temperatures (4, 8, 10, 13, and 16 °C). The effects of 5 CO₂ concentrations (0, 2, 5, 10, 15%) at two O₂ levels (2 and 20%) were also examined at these temperatures. Mushroom respiration increased with temperature following an Arrhenius-type relationship; activation energies and corresponding Q₁₀ values were calculated. Lowering the oxygen concentration significantly decreased the respiration rate. The effects of reducing O₂ levels were greater at higher storage temperatures. Both activation energies and Q₁₀ values were lower under reduced O₂ atmospheres compared with those in air. A Michaelis–Menten enzyme kinetics model was evaluated for describing the influence of gas concentrations on respiration rate. The effects of O₂ fitted the O₂ enzyme kinetics model well. CO₂ exhibited small inhibitory effects on respiration of whole and sliced mushrooms, especially at low O₂ concentrations and low temperatures. The enzyme model was used to predict respiration under an optimal modified atmosphere for mushrooms, and the required film O₂ and CO₂ permeabilities were defined for key pack design parameters.     

Inhibition of Fungal Growth on Wheat and Rye Bread by Modified Atmosphere Packaging and Active Packaging Using Volatile Mustard Essential Oil

ABSTRACT: Wheat and rye bread artificially inoculated with molds were packed in modified atmospheres of 0%, 50%, 75%, or 100% CO₂ balanced with N₂, and 3 levels of residual O₂, 1%, 0.03%, or <0.01%/O₂-absorber, and stored for 30 to 35 d. Modified atmosphere packaging (MAP) was quantitatively more effective for rye bread because fewer mold species grew at elevated CO₂. However, the major rye bread contaminant, Penicillium roqueforti , was the overall most CO₂-resistant mold and only the use of O₂-absorber could prevent growth of this species. On wheat bread, the most CO₂-tolerant mold was Penicillium commune , growing in 99% CO₂ (with high residual O₂), and Aspergillus flavus was the mold species that grew at lowest O₂ in 75% CO₂ treatment. The spoilage yeast/"chalk mold" Endomyces fibuliger was less affected by the different O₂ levels than the true filamentous molds, and none of the tested MAP treatments could prevent growth, but lag-phase was increased with O₂-absorber on wheat bread and decreased with 1% residual O₂ on rye bread. Experiments with volatile mustard oil showed that A. flavus and Eurotium repens were the most mustard oil-resistant species on wheat and rye bread, respectively. A combination strategy with MAP and mustard oil proved most optimal, and total inhibition was achieved with 2 μL mustard oil/rye bread slice and between 2 and 3 μL/wheat bread. Results indicated that the nature and surface area of the product influences effectiveness of active packaging with mustard oil.     

Mathematical modelling of O2 consumption and CO2 production rates of whole mushrooms accounting for the effect of temperature and gas composition

Investigation of respiration rate of fresh produce, under different gas composition and temperatures, and respective mathematical modelling is central for the modified atmosphere packaging design. This work investigates the effect of temperature (4, 8, 12, 16, 20 °C) and gas composition (O₂ between 3 to 21% and CO₂ between 0 to 15%) on respiration rate of whole mushrooms. Oxygen and carbon dioxide respiration rates increased significantly (3–4 fold) as the temperature elevated from 4 to 20 °C and were in the range of 13.23 ± 3.12 to 102.41 ± 2.132 mL kg⁻¹ h⁻¹) and 14.33 ± 1.56 to 97.02 ± 2.51 mL kg⁻¹ h⁻¹) respectively. Low O₂ and high CO₂ levels reduced O₂ consumption and CO₂ production rates of whole mushrooms on average by a circa 47–60% at all temperatures as compared to the respiration rate at ambient air. Mathematical models were developed for RO₂ and RCO₂, by combining the Arrhenius and Michaelis–Menten uncompetitive equations. These models predicted well, O₂ consumption and CO₂ production rates of whole mushrooms as a function of both temperature and gas composition.     

EFFECTS of CONTROLLED ATMOSPHERE ON QUALITY of MINIMALLY PROCESSED APPLE (cv. JONAGORED)

Controlled atmosphere (2% O₂+ 4% to 12% CO₂) storage was found to be advantageous over air storage in terms of overall preservation of fresh-cut apple (cv. Jonagored). After 3 days, CA-stored apple cubes were firmer, showed better color and higher content of fructose and soluble solids content than air-stored cubes. In relation to color preservation this benefit was increased when CO₂ in the atmosphere was increased to 12% CO₂. Controlled atmosphere storage showed no advantage over air storage in relation to sensory evaluation of firmness and flavor.     

MODIFIED ATMOSPHERE PACKAGING of SWEET CORN ON COB

Respiration rates (RR) of two varieties of sweet corn on cob were determined at O₂ concentrations: 5, 10, 15, and 21% and CO₂: 0, 5, and 10%, and temperatures: 2, 12, and 25C. Temperature and O₂ had strong influence on RR. Activation energies for effect of temperature on RR(O₂) and RR(CO₂) were, 44.6 and 104.4 kJ/mole, respectively. At 12C, to maintain 4% O₂ and 6% CO₂ in a package 10.8 cm² area, with 1.12 kg of corn, the estimated film permeabilities were 14 ml O₂/h.cm² and 65 ml CO₂/h.cm², respectively. Experimental and theoretical transient gas concentrations using microporous films were in reasonable agreement, but the desired O₂ and CO₂ levels were not achieved.     

Chemical, Microbiological, and Sensory Quality of Cod Products Salted in Different Brines

ABSTRACT: Studies were carried out on the effect of different brines containing high concentrations of calcium chloride (CaCl₂, 0.8%w/w), magnesium chloride (MgCl₂, 0.4%w/w), and potassium chloride (KCl, 50%) on the chemical (chloride and moisture contents), microbial (total viable counts, total coliforms, enterococci, and staphylococci), and sensory quality of salted cod. The brines were prepared from combinations of the Ca, Mg, and K ions and sodium chloride (NaCl) at pH 6.5 and 8.5. Additionally, 3 salts (one composed solely of NaCl, another commercial sea salt from the southern Europe and, finally, a natural salt from northern Europe) were also tested. Principal component analysis structured the chemical and microbiology data in 3 clusters: (1) an extreme cluster, formed by cod brined in the commercial sea salt, which achieved the highest microbiological counts, namely 4.1 log CFU/g on plate count agar (PCA) and 1250 coliforms/g; (2) an intermediate cluster composed of cod salted in brine containing 50% NaCl, 0.4% MgCl₂, and 49.6% KCl (pH 6.5); and (3) a central cluster, including all the other treatments, which presented the lowest microbiological counts, namely 2.4 log CFU/g on PCA and 20 coliforms/g. Although the batches of the intermediate cluster presented slightly higher total viable and staphylococci counts than the central cluster, the presence of Mg and K ions improved the color of the salted product. In the assayed concentrations, CaCl₂, MgCl₂, and KCl can be used in the brining of cod without adversely affecting the microbiological and sensory quality of the salted cod.     

The Effects of Residual Oxygen on the Storage Life of Retail-Ready Fresh Beef Steaks Masterpackaged Under a CO2 Atmosphere

ABSTRACT:  Retail-packed rump ( Gluteus medius , GM) and striploins ( Longissiumus dorsi, LD) steaks were masterpackaged under carbon dioxide (CO₂) and stored at 1 °C ± 1 °C for 14, 28, 35, and 42 d. A commercial oxygen (O₂) scavenger (ATCO HV1000®, Standa Industrie, Caen, France) was used in the masterpacks to achieve an O₂-free atmosphere. Similar packages without the O₂ scavengers were also prepared. At each storage time, 2 masterpacks of each treatment were opened and the retail trays were placed in a display case at 4 °C ± 2 °C for 1 and 48 h for microbiological and sensorial evaluations. The low growth rate of aerobic psychrotrophic flora on the stored beefsteaks demonstrated the bacteriostatic effect of CO₂ during storage. The maximum level of psychrotrophic aerobic bacteria reached during storage was approximately 10⁶ CFU/g. The steaks stored in masterpacks with scavengers bloomed to the desirable red color associated with freshly cut meat in the display case for all of the storage periods, except in the case of GM steaks, which showed a cycle of transient discoloration. GM and LD steaks were well accepted (65% and 82%, respectively) after 42 d under CO₂ at 1 °C ± 1 °C. The GM and LD steaks stored without the O₂ scavenger showed variable fractions of discoloration that significantly detracted from the appearance of the samples.     

Influence of oxygen concentration and temperature on respiratory characteristics of fresh-cut green onion

The characteristics of the respiration rates in precut green onion, as influenced by oxygen levels and temperature, were examined to provide design factors for modified atmosphere packaging (MAP). Fresh-cut green onions ( Allium fistulosum L.) were prepared and sealed, with and without a CO₂ absorbent, in gas-tight glass containers that had initially been purged with air or a gas mixture (O₂ 9%/N₂ balance). The containers were stored at different temperatures (0, 10, 20 °C). At 10 °C, the maximum O₂ uptake rate (V_m) and the O₂ concentration at half-maximum (K_m) uptake rate were 30.95 mL kg⁻¹ h⁻¹ and 1.63%, respectively. Regardless of temperature, the lower O₂ limit was estimated to be about 1.0% O₂ on the basis of respiratory quotient (RQ) increase. Respiration of cut green onion was dependent on O₂ concentration as well as temperature, as shown by applying the Michaelis–Menten type model and the Arrhenius equation. However, the presence of CO₂ had little effect on O₂ uptake of cut green onion at relatively high O₂ concentrations (≤20%).     

MODIFIED ATMOSPHERE PACKAGING of HEAD LETTUCE

Magnitudes of respiration rates of lettuce heads at O₂ levels: 5, 10, 15, and 21%, and three temperatures: 2, 12, and 25C ranged between 3 to 30 ml O₂/kg.h. Oxygen concentration (O₂). temperature (T), storage time (t), and the interactions between temperature and O₂ (T*O₂) and temperature and time (T*t), affected respiration rates. Predicted and experimental O₂ and CO₂ concentrations in packages using two plastic films were in good agreement with each other. However, steady state gas concentrations were achieved after about 90 h.     

Color Development of Squid Skin as Affected by Oxygen Concentrations

ABSTRACT:  Color development of squid skin was controlled by O₂ concentration for storage. When stored above 10% O_2, the color index (CI) as an index of color development of skin increased in 24 h, and decreased gradually with further storage. The CI profile at 10% O₂ was practically identical to that in air. When stored at 0.1% O₂, in the presence of N₂, the CI increased partly in 6 h and decreased. Morphological observation of chromatophore distinguished the CI increase at 0.1% and 10% O₂ by their shape and size distribution. However, the storage of squid at O₂ concentration between 2.5% and 7% practically did not change the CI for at least 48 h. ATP content of skin was kept unchanged when the storage atmosphere contained O₂ concentration at 2.5% up to 48 h, while the content decreased rapidly with a half decrease in 6 h when stored at 0.1% O₂. It was demonstrated clearly that ATP is regenerated in the presence of O₂, but the ATP concentration did not determine the CI change during the storage. Exposure to high concentration of O₂ might induce a full color development of squid skin.     

Respiration Rate of Sweet Cherries: 'Burlat', 'Sunburst' and 'Sweetheart' Cultivars

ABSTRACT: Oxygen depletion and CO₂ formation were measured using a closed system method at various temperatures. No CO₂ inhibition effect was observed. Respiration rates were related to O₂ concentration by a simple Michaelis-Menten equation. Lineweaver-Burk plots of respiratory rate versus O₂ concentration were nonlinear over the whole O₂ concentration range explored. However, this type of analysis allowed us to differentiate two O₂ concentration intervals (above and below 10%) in which the double reciprocal plots are linear. Respiration rates decreased with decreasing temperature following the Arrhenius law. The Michaelis-Menten equation constants V_m and K_m for the 3 cultivars at 2, 5, and 20°C are tabulated.