Efficacy of the combined application of oregano and rosemary essential oils for the control of Escherichia coli,Listeria monocytogenes and Salmonella Enteritidis in leafy vegetables

This study assessed the effect of the combined application of essential oils (EOs) from Origanum vulgare L. – oregano (OVEO) and Rosmarinus officinalis L. – rosemary (ROEO), alone or in combination at subinhibitory concentrations, against three pathogenic bacteria that are associated with fresh leafy vegetables: Listeria monocytogenes (L. monocytogenes), Escherichia coli (E. coli) and Salmonella enterica Serovar Enteritidis (S. Enteritidis). The inhibitory effects were evaluated by determining the minimum inhibitory concentration (MIC) and the fractional inhibitory concentration index (FICI) and assessing the viable cell counts in vegetable broth and artificially infected vegetables over time. Still, the effects of the EOs on native spoilage native flora were assessed. The MIC of OVEO was 0.6 μL/mL against the test strains either in single and mixed inoculum. The MIC of ROEO was 5 μL/mL against L. monocytogenes and E. coli and 10 μL/mL against S. Enteritidis in single inocula, whereas it was 10 μL/mL against the mixed inoculum. The FICI of the combined EOs was 0.5 against the mixed bacterial inoculum, which suggested a synergic interaction. The incorporation of OVEO and ROEO alone (MIC) or combined at different subinhibitory concentrations in vegetable broth resulted in a decrease in the viable cell counts of all test strains over 24 h. Similarly, the EOs alone or in the tested combinations reduced the viable cell counts of all test strains in experimentally infected fresh vegetables, besides to decrease the counts of spoiling native flora (mesophilic bacteria, enterobacteria and fungi). These findings reinforce the rational for the use of OVEO and ROEO in combination at subinhibitory concentrations to guarantee the safety and extend the shelf life of fresh vegetables.     

Effect of orange dietary fibre,oregano essential oil and packaging conditions on shelf-life of bologna sausages

The objective of this work was to study the effect of orange dietary fibre (1%) (ODF), oregano essential oil (0.02%) (OEO) and the storage conditions (vacuum, air and modified atmosphere) on the shelf-life of bologna sausage. Samples with ODF + OEO stored in vacuum packaging showed the lowest TBA values. ODF + OEO samples stored in vacuum packaging showed the lowest aerobic and lactic acid bacteria counts. The sensory evaluation scores were similar for samples with ODF + OEO and stored either in air or vacuum packaging. Orange dietary fibre and oregano essential oil could find a use in the food industry to improve the shelf-life of meat products.     

Effects of UV-C on physicochemical quality attributes and Salmonella enteritidis inactivation in liquid egg products

The perspectives of UV-C radiation as a non-thermal treatment for liquid egg products were evaluated from the point of view of the effects on egg quality attributes and the decontamination efficiency against the main egg contaminant Salmonella enterica subsp. enterica Ser. Enteritidis. UV-C treated egg fractions (egg yolk, egg white and whole egg) were analyzed for changes in pH, color, temperature-dependent viscosity and TBARS index, and were inoculated with S. enteritidis (ATCC 13076). Contrary to heat treatments, UV-C was not affecting viscosity and pH. Browning due to Maillard was perceptible in egg yolk and whole egg at low UV-C doses, but the corresponding browning indexes were always lower than in heat pasteurized egg fractions. Major changes were only due to lipid oxidation. TBARS values at the highest UV-C doses were larger than in pasteurized egg yolk and whole egg; under dynamic conditions and 0.61 J cm^?2, results were not significantly different to natural untreated samples. And UV-C was effective to inactivate S. enteritidis. In egg white, a load reduction up to 5.3 log₁₀ was achieved under dynamic conditions (9.22 J cm^?2, 39 min), while 3.3 log₁₀ and 3.8 log₁₀ reductions were recorded in egg yolk and whole egg. Static treatments were less efficient, but still, load reductions between 1.7 and 2.8 log₁₀ were obtained. At 3.94 mW cm^?2, time necessary to achieve a 4D reduction of Salmonella cells was estimated to be around 7.4 min in egg white.     

Synergistic effect of high hydrostatic pressure treatment and food additives on the inactivation of Salmonella enteritidis

The synergistic effect of high hydrostatic pressure (HHP) treatment and food additives (FAs) on the inactivation of Salmonella enteritidis was investigated. At 1% concentrations, all of the FAs tested showed significant synergistic effects, and 9 of 30 FAs showed strong synergistic effects. Citric acid, adipic acid, C8-sugarester, C10-sugarester, tannin, nisin, wasabi extract, ε-polylysine, and protamine each showed a strong inactivation effect when administered alone at the 1% level. In the HHP treatment at 250 MPa for 30 min, the minimum effective concentrations of C8-sugarester, C10-sugarester, and protamine were 0.25, 0.125, and 0.06%, respectively. These results indicate that some FAs are useful for increasing the inactivation ratio of S. enteritidis in HHP treatment.     

Improving the shelf life of low-fat cut cheese using nanoemulsion-based edible coatings containing oregano essential oil and mandarin fiber

Nanoemulsion-based edible coatings containing oregano essential oil (OEO) as antimicrobial were applied onto low-fat cut cheese to extend its shelf life. Nanoemulsions formulation was 2.0% (w/w) sodium alginate, 0.5% (w/w) mandarin fiber, 2.5% (w/w) Tween 80 and 1.5%, 2.0% or 2.5% (w/w) of OEO. Particle size, ζ-potential, apparent viscosity and whiteness index of nanoemulsions were assessed. Water vapor resistance of coatings was evaluated as well as their antimicrobial efficiency against inoculated Staphylococcus aureus and native microbiota growth during refrigerated storage. Headspace gases were measured as an indicator of bacterial activity and sensory alterations such as color and texture of cheese pieces were studied. Coatings with at least 2.0% (w/w) OEO decreased Staphylococcus aureus population from 6.0 to 4.6 log CFU/g after 15 days. Coated-cheese pieces containing 2.5% (w/w) OEO inhibited psychrophilic bacteria or molds and yeasts growth during 6 or 24 days of storage, respectively. Consequently, the atmosphere into the sealed tracks was stabilized and the outward appearance of cheese pieces was preserved. Thus, the present work evidences the feasibility of using mandarin fiber with high nutritional properties and sodium alginate acting as texturizing agents, to form OEO-loaded coatings onto low-fat cut cheese in order to extend its shelf life.     

Application of high-pressure processing and polylactide/cinnamon oil packaging on chicken sample for inactivation and inhibition of Listeria monocytogenes and Salmonella Typhimurium,and post-processing film properties

The synergistic effects of combined high-pressure (HP) treatment and active packaging consisting of polylactide (PLA), polyethylene glycol (PEG) and cinnamon oil (CIN) on the inactivation and inhibition of Listeria monocytogenes and Salmonella Typhimurium in chicken samples during the refrigerated storage were assessed. The target was to decrease the treatment pressure intensity of the traditional HP technology and cinnamon oil concentration so that the process becomes more economically viable. The CIN concentration was varied from 7 to 17% in the plasticized film (PLA/PEG 80/20). It was observed that the most effective treatment was the combination of a pressure treatment at a level of 300 MPa, and packaging the chicken sample in an active packaging containing 17% CIN, which reduced the population of the pathogens to a safe level during 21 days of refrigerated storage. Furthermore, the impact of HP and CIN on the thermal, rheological and mechanical properties of those films was evaluated. Time-temperature superposition principle indicated that the mechanical properties of those films remained intact after the HP-treatment, and at high temperature. Therefore, the developed films could be used for packaging of chicken samples under high-pressure, and high-temperature with maintaining the packaging integrity and the food safety at the highest level.     

Antimicrobial efficacy of cinnamon oil against Salmonella in almond based matrices

Reduced moisture enhances resistance of Salmonella and subsequently reduces the antimicrobial efficacy of thermal treatment. Alternative and supplementary non-thermal intervention methods are urgently needed. In this study, Cinnamonum cassia oil was tested for its antimicrobial effect against outbreak strains Salmonella Enteritidis PT30 and S. Tennessee K4643. Minimal inhibitory concentration and minimal bactericidal concentration for both strains were 0.05% (v/v) and 0.1% (v/v), respectively. Death curves showed that including 0.1% and 0.15% (v/v) C. cassia oil resulted in ∼7 Log reduction of bacteria within 2 h and 1 h, respectively. However, the antimicrobial efficacy of C. cassia oil was reduced when S. Enteritidis PT30 existed in low moisture condition. When S. Enteritidis PT30 was established on almonds/paper discs, 0.4% C. cassia oil resulted in ∼1.7 Log₁₀ CFU/almond or 3.2 Log₁₀ CFU/disc reduction within 2 h at room temperature, respectively. S. Enteritidis PT30 established on both almonds and paper discs were very stable, there was only a 0.80 Log₁₀ CFU/almond and 1.20 Log₁₀ CFU/disc reduction during 9-week and 7-week storage at room temperature, respectively. C. cassia oil intervention increased S. Enteritidis PT30 reduction on both almonds and paper discs during storage with more reduction on paper discs. 0.4% C. cassia oil treatment reduced S. Enteritidis PT30 on paper disc to undetectable level within 4 weeks, but only led to 2 Log₁₀ CFU reduction on almonds, indicating a protection effect from the almond matrix or almond surface components. Additionally, S. Enteritidis PT30 established on paper disc coated with almond surface components exhibited higher resistance to desiccation and C. cassia oil treatment, further demonstrating the protection role of food matrix. In conclusion, C. cassia oil is effective against S. Enteritidis PT30 and S. Tennessee K4643, but its antimicrobial efficacy against the tested Salmonella was compromised by low moisture environment and food matrix.     

Efficacy of aqueous chlorine dioxide and fumaric acid for inactivating pre-existing microorganisms and Escherichia coli O157:H7, Salmonella typhimurium,and Listeria monocytogenes on broccoli sprouts

The combined effect of aqueous chlorine dioxide (ClO₂) and fumaric acid as a chemical treatment to inactivate pre-existing microorganisms was evaluated using broccoli sprouts. Broccoli sprouts were treated with distilled water, 50 ppm ClO₂, 0.5% fumaric acid, and a combination of 0.5% fumaric acid and 50 ppm ClO₂. Treatment with 50 ppm ClO₂ and 0.5% fumaric acid reduced the initial populations of total aerobic bacteria, yeasts and molds, and coliforms in broccoli sprouts by 2.70, 2.46, and 1.71 log CFU/g, respectively. In addition, the combined treatment of 50 ppm ClO₂ and 0.5% fumaric acid reduced the initial populations of Escherichia coli O157:H7, Salmonella typhimurium, and Listeria monocytogenes inoculated on broccoli sprouts by 2.39, 2.74, and 2.65 log CFU/g, respectively, compared to the control. These results suggest that the combination of aqueous ClO₂ and fumaric acid can be useful as a hurdle for extending the shelf life of broccoli sprouts during storage.     

Antimicrobial effect of koruk (unripe grape—Vitis vinifera) juice against Salmonella typhimurium on salad vegetables

To evaluate the antimicrobial activity of koruk (unripe grape—Vitis vinifera) juice, cucumber and parsley samples were inoculated with two Salmonella typhimurium strains namely S. typhimurium NRRL-B-4420 and S. typhimurium CCM 583 at the level of approximately 10⁶ cfu/ml. The samples were treated with koruk juices produced by different methods (by using mortar and electrical blender) for 0, 15, 30 and 60 min. Salmonella cells were counted by using direct surface plating (on Tryptone Soya Agar, Bismuth Sulphite Agar or Xylose Desoxylate Agar with 50 ppm nalidixic acid; TSAN, BSAN or XLDN) and overlay plating (on TSAN/BSAN) methods. Counts on TSAN/BSAN or TSAN, BSAN and XLDAN were not significantly different (P > 0.05). So, further experiments were done with direct surface plating on TSAN and BSAN. Overall statistical analysis indicated that, the antimicrobial effect of koruk juice was found to be dependent on the culture strains and products used (P < 0.05). Koruk juice exerted an immediate antimicrobial effect contact with the test microorganisms causing 1–1.5 log cfu/g reductions in initial populations. However, cell reductions in samples exposed to koruk juice for 15, 30 and 60 min varied between 2 and 3.5 log cfu/g depending on the microorganism and test sample used. There was no significant difference in cell reduction in samples exposed to koruk juices for 15, 30 and 60 min (P > 0.05) whereas reduction obtained at 0 time differed significantly (P < 0.05). On the other hand, no significant differences were found between the antimicrobial effects of koruk juices prepared by different methods. Results of the study showed that koruk juice used as flavouring and acidifying agent in Turkish kitchens, may be considered to be an alternative potential antimicrobial agent at household level for salad vegetables.     

Thermal inactivation of Salmonella Typhimurium on dressed chicken skin previously exposed to acidified sodium chlorite or carvacrol

Salmonella is a leading cause of foodborne illness and live poultry is a main reservoir of this pathogen, worldwide. Cross-contamination and transportation of contaminated poultry meat act as an important vehicle of Salmonella infections in humans. In this study, we assessed the effect of two antimicrobials; acidified sodium chlorite (ASC) and carvacrol followed by thermal treatment to inactivate Salmonella Typhimurium on dressed chicken skin. D-values (time in min for the pathogen to decrease by 90%) of Salmonella Typhimurium at 56, 60 and 64 °C on dressed chicken skin in the control samples, determined by linear regression, were 6.17, 3.16, 1.32 min, respectively. Two D-values calculated using a logistic model, ranged from 6.28 (D_1, major population, plus T_L) and 11.66 (D_2, heat-resistant subpopulation, plus T_L) min at 56 °C to 1.08 (D₁ plus T_L), and 2.07 (D₂ plus T_L) min at 64 °C. Pre-dipping in 100–300 ppm ASC or 0.02–0.06% carvacrol rendered the pathogen more sensitive to the lethal effect of heat. Thus, combination of antimicrobials with thermal inactivation was more effective in reducing heat resistance of the pathogen on dressed chicken surface. The model developed will assist poultry processors in estimating the time required for specific log reductions of Salmonella Typhimurium on chicken skin and thus, will contribute in designing acceptance limits at critical control points for chicken skins at lower times and temperatures for cooking.     

Modelling the effect of pH and pectin concentration on the PEF inactivation of Salmonella enterica serovar Typhimurium by using the Monte Carlo simulation

The effects of pH (3.5, 4 and 4.5), electric field (15, 25, 35 and 40 kV/cm) and pectin concentration (0.1, 0.3 and 0.6%) on the inactivation kinetics of Salmonella typhimurium in an orange juice-milk beverage treated by pulsed electric fields (PEF) were studied. A secondary model, based on Weibull distribution function, was used together with a Monte Carlo simulation to establish the most influential factors on the final number of Salmonella cells after PEF treatment. The Monte Carlo simulation can be a useful and practical tool for the industry to predict how the process parameters and product formulation will influence the food safety of the product.     

Comparative study of thermal inactivation kinetics of Salmonella spp. in peanut butter and peanut butter spread

Peanut butter has been implicated in multi-state outbreaks of salmonellosis in recent years. Studies have shown that Salmonella exhibited increased thermal resistance in peanut butter. However, little is known about the effect of product formulation on the kinetics of survival of Salmonella during thermal treatment. Therefore, the objective of this research was to compare the thermal resistance of Salmonella in four commercially available peanut butter and spread products, and evaluate the effect of product formulation on the survival of this pathogen during heating.Four peanut butter and spread samples, including Omega 3 (A), regular fat (B), reduced sugar (C), and reduced fat (D), inoculated with a 6-strain cocktail of Salmonella spp., were heated at 70, 75, 80, 85, and 90 °C. Experimental results showed that the highest thermal resistance of Salmonella was found in the samples with reduced fat, while the least in the samples with Omega 3 formulation. No significant difference in the bacterial thermal resistance was observed in the regular fat and reduced sugar formulations. The Weibull survival model was used to describe the survival curves. Results showed that the average exponent (shape factor) of the model ranged from 0.38 to 0.662, suggesting progressively decreased rate of inactivation during heating. The scale (rate) coefficients of the model increased linearly with temperature. The calculated minimum lethal temperature for Salmonella was 54.8, 59.8, 59.5, and 63.9 °C in samples A, B, C, and D, respectively. No tail effect was observed. The results of this study suggest that proper formulation of peanut butter and spread may enhance thermal inactivation of Salmonella.     

Efficacy of pulsed electric fields for the inactivation of indicator microorganisms and foodborne pathogens in liquids and raw chicken

This study investigated the ability of pulsed electric fields (PEF) to inactivate a range of microorganisms in liquid media and on raw chicken meat. The susceptibilities of ten Campylobacter isolates (seven Campylobacter jejuni isolates and three Campylobacter coli isolates), Escherichia coli (ATCC 25922) and Salmonella Enteritidis (ATCC 13076) to PEF in liquid media were investigated. All Campylobacter isolates tested in liquid were susceptible to PEF treatment (65 kV/cm, 5 μs, 500 Hz) with reductions of between 4.33 and 7.22 log₁₀ CFU/mL observed for the longest treatment (30 s). Significant differences in susceptibility were observed between Campylobacter isolates subjected to equivalent PEF treatments ranging from 2.41 to 5.19 log₁₀ CFU/mL. Campylobacter isolates processed in liquid media were found to be more sensitive to PEF than E. coli and S. Enteritidis (P < 0.05). The application of PEF (3.75 and 15 kV/cm, 10 μs, 5 Hz) to inoculated samples of raw chicken did not result in any significant reductions in total viable counts, Enterobacteriaceae, C. jejuni, E. coli or S. Enteritidis. Therefore, under the conditions used in this study, PEF technology may not be suitable as a food safety intervention measure for the control of microbial contaminants on broilers during processing although it may have potential to reduce contamination of process water (e.g. scald or spin chill water).     

Efficacy of a heat-spray and heat-double spray process on inoculated nuts with Salmonella enteritidis ATCC 1045

Due to Salmonella outbreaks in almonds, regulatory standards have been established, requiring that almonds for human consumption in North America must achieve a minimum of 4 log₁₀ CFU/g reduction of Salmonella. This study investigated a system using a combination of heating and transient application of ethanol to reduce bacterial load. This approach used a small scale heat-spray and heat-double spray process that included a two factor block design with heat (25±2 °C and 125±2 °C) and spray levels (0,1,2); One factor design with nut levels of almonds, pistachios, pecans, and walnuts for each heat-spray and heat-double spray process; a two factor experiment included a dip contact time (5s, 1800s) and ethanol evaporation time (5 s, 1800 s). Also, to evaluate the interaction of a heat-spray process on moisture content of almonds, a two factor design with levels of heat (25±2 °C and 125 ± 2 °C) and spray (0,1) was used. Additionally, the spray evaporation rate was evaluated. The heat-spray process shows additivity, while the heat-double spray process shows synergism. The heat-double spray process on almonds achieved a 6.1 mean log₁₀ CFU/g reduction of Salmonella that was 35% higher than that of the heat-spray. For other nuts, the heat-double spray process led to a 4.8, 3.0, and 4.0 log₁₀ reduction for pecan, pistachio, and walnut, respectively. The dip time (p < 0.05) had a greater effect than ethanol evaporation (p > 0.05) on log₁₀ reduction of Salmonella in almonds. By applying ethanol 70%, the moisture increases by ∼0.5% w.b., whereas applying temperature decreases moisture by ∼2% w.b. The implication of these findings is that both the heat-spray and heat-double-spray process may be alternatives to the current almond disinfection processes in achieving a high log₁₀ reduction.     

Synergetic antibacterial efficacy of cold nitrogen plasma and clove oil against Escherichia coli O157:H7 biofilms on lettuce

This study aims to evaluate the antimicrobial effects of cold nitrogen plasma (CNP) and clove oil against Escherichia coli O157:H7 (E. coli O157:H7) biofilm on lettuce. Both clove oil (1 mg/mL, 2 mg/mL and 4 mg/mL) and CNP (400–600 W) displayed significant eradication effect on E. coli O157:H7 biofilms in vitro (p < 0.001). Subsequently, the antibiofilm effect of combined treatment was studied as well. Compared with the respective treatment, combined treatment exhibited remarkable synergistic effect on eradicating E. coli O157:H7 biofilms. The confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) had also visually testified that the antibacterial effects of clove oil on E. coli O157:H7 biofilms (in vitro and on lettuce) were enhanced by CNP at 400 W for short treatment duration. The results of sensory evaluation indicated that combined treatment has mild negative effect on lettuce quality. Moreover, the synergetic antibacterial mechanism of clove oil and CNP against E. coli O157:H7 was concluded as that they could damage the bacterial cell wall and the outer membrane, leading to leakage of cellular components, such as nucleic acid and ATP.     

Zinc oxide nanoparticles loaded active packaging,a challenge study against Salmonella typhimurium and Staphylococcus aureus in ready-to-eat poultry meat

Zinc oxide nanoparticles were prepared using hydrothermal synthesis approach. Formation of zinc oxide nanoparticles were confirmed by using UV–Vis spectrophotometer, Fourier transform infrared spectrometer and X-ray diffractometer. The particles size (≤100 nm) and structure of nanoparticles were studied under scanning and transmission electron microscope. The nanoparticles were used against two prominent foodborne pathogens, Salmonella typhimurium and Staphylococcus aureus and were found highly effective against both of them. The antibacterial activity of the nanoparticles was determined in solid and liquid media using nutrient agar and broth. Zinc oxide nanoparticles loaded active film of calcium alginate was prepared for active packaging against the same foodborne pathogens (S. typhimurium and S. aureus). Presence and distribution of nanoparticles in active film were confirmed with Fourier transform infrared spectrometer, X-ray diffractometer and scanning electron microscopy. Zinc oxide nanoparticles loaded active films showed antibacterial activity against the target bacteria in Petri dish. The film was also used as an active packaging (a challenge study) in ready-to-eat poultry meat against the same pathogens, and reduced the number of inoculated target bacteria from log seven to zero within 10 days of its incubation at 8 ± 1 °C.     

Effect of hydrogen peroxide vapor treatment for inactivating Salmonella Typhimurium,Escherichia coli O157:H7 and Listeria monocytogenes on organic fresh lettuce

In this study, the efficacy of hydrogen peroxide vapor (HPV) for reducing Salmonella Typhimurium, Escherichia coli O157:H7 and Listeria monocytogenes on lettuce was investigated as well as its effect on lettuce quality. Lettuce was inoculated with a cocktail containing three strains of each pathogen then treated with vaporized hydrogen peroxide for 0, 2, 4, 6, 8 and 10 min. The concentrations of hydrogen peroxide used were 0, 1, 3, 5 and 10%. With increasing treatment time and hydrogen peroxide concentration, HPV treatment showed significant (P < 0.05) reduction compared to the control (0%, treated with vaporized distilled water). In particular, vaporized 10% hydrogen peroxide treatment for 10 min was the most effective combination for reducing the three pathogens on lettuce. The reduction levels of S. Typhimurium, E. coli O157:H7 and L. monocytogenes on lettuce were 3.12, 3.15 and 2.95 log₁₀ CFU/g, respectively. Furthermore, there were no significant (P > 0.05) quality changes (color and texture) of lettuce among all tested samples, and hydrogen peroxide residues were not detected after 36 h storage time in any of the treated samples. These results suggest that HPV treatment could be an alternative method for reducing S. Typhimurium, E. coli O157:H7 and L. monocytogenes on fresh produce.     

Rapid real-time loop-mediated isothermal amplification combined with coated activated carbon for detection of low numbers of Salmonella enterica from lettuce without enrichment

A real-time loop amplified (Rti-LAMP) DNA assay system was developed for the rapid detection of low numbers of Salmonella enterica ser. Enteritidis (S. enterica) on the leaves of romaine lettuce without enrichment. The assay involved seeding 50 g portions of leaves with various numbers of S. enterica CFU. The lowest level of DNA consistently detected by the Rti-LAMP assay was that from 25 CFU per 50 g (0.5 CFU/g) of lettuce equivalent to the DNA from 6 CFU per Rti-LAMP reaction. A standard curve was generated by plotting the Tp values (min) against the log of 6, 25, 60 and 250 CFU of S. enterica seeded onto 50 g of lettuce. The entire assay could be completed in 3.5 h.7     

Effect of γ irradiation on quality-maintaining of fresh-cut lettuce

The effects of irradiation on microorganisms and physiological quality of fresh-cut lettuce were evaluated during storage at 4 °C. The total bacterial counts on fresh-cut lettuce irradiated with 1.0 kGy were reduced by the order of 2.35 Log CFU/g, and the total coliform group were lowered to less than 30 MPN (most probably number)/100 g. The polyphenoloxidase activity of fresh-cut lettuce was significantly inhibited by irradiation. In addition, the loss of vitamin C of fresh-cut lettuce irradiated with 1.0 kGy was significantly (α = 0.05) lower than that of non-irradiated. The best treatment of maintaining quality of fresh-cut lettuce appeared to be 1.0 kGy irradiation.     

二类油层聚驱油层动用状况分析

通过本文,明确了不同相别砂体动用差异的影响因素,采取优化注聚体系参数等措施,使油层动用程度保持较高水平。