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1.
《Food Control》2014
Lower thermal load on foods is desirable for food producers and consumers as the food gets higher quality. With reduced thermal load, the investigation of food safety is of importance. In this study, microbial inactivation efficacy of a new retort process with high frequency longitudinal agitation was compared to static retort process which was used as a benchmark. As a model, fish soup samples, inoculated with approximately 108 cells/ml Listeria innocua, was exposed to mild heat treatments at 62, 65 and 68 °C. Results clearly demonstrated that agitating mode can provide equivalent lethality to the model organism L. innocua within significantly shorter heating times compared to static mode. Bacteria were not detected on TSA-YE plates after 11.5, 6.8 and 5.5 min processing in agitating mode; 77, 67 and 52 min processing in static mode at 62, 65 and 68 °C respectively. Bacterial inactivation in agitating mode was generally correlated with estimated inactivation based on product core temperature, D- and z-values for L. innocua. This may indicate that distribution of the heat load over the soup was enhanced through agitation. Results showed that utilization of high frequency longitudinal agitation mechanism in retorts is promising for reducing the thermal load on food products without compromising on food safety related to non-spore forming pathogens. 相似文献
2.
《Food Control》2015
Understanding the influence of fruit surface morphology on ultraviolet-C (UV-C 254 nm) inactivation of microorganisms is required for designing effective treatment systems. In this study, we analyzed UV-C inactivation of Penicillium expansum that was inoculated onto the surface of organic fruits. Results show that maximum reductions of 1.8 (apple), 2.4 (cherry), 2.6 (strawberry) and 2.8 (raspberry) log CFU/g were observed after 1.2, 2.1, 3.3, and 3.3 kJ/m2 of UV-C doses, respectively. The UV doses required to reduce 2 log CFU/g of P. expansum population on apples, cherries, strawberries, and raspberries estimated with the Weibull equation were 1.03, 1.28, 1.39, and 1.61 kJ/m2, respectively. Findings also show that the hydrophobic nature of raspberries, along with high surface roughness, resulted in a lower inactivation rate of P. expansum. This study shows that UV-C effectively reduces P. expansum populations on fresh fruit surfaces; however, the efficacy of treatment is dependent on fruit surface morphology. 相似文献
3.
叶轮式搅拌反应器有很广泛的应用 ,其内部的流动是很复杂的三维流动 ,该文应用计算流体力学方法对搅拌反应器内流体的三维流动进行了计算机数值模拟 ,在分析计算中采用了移动网格技术 ,这种方法不需要实验数据辅助 ,通过与实验结果的对比 ,可以看出 ,计算结果与实验结果有很好的一致性 ,使用计算流体力学方法也可以直接计算出流体的流动形态 ,这可以使我们更好的理解搅拌反应器内复杂的流动情况 ,为搅拌反应器的设计制造提供了有效的参考手段 相似文献
4.
《Food Control》2014
High pressure processing (HPP) is used as a post-process decontamination treatment to ensure that cooked chicken is free from Listeria monocytogenes and other food poisoning bacteria. However HPP does not inactivate bacterial endospores and the conditions in cooked chicken could support the growth of Clostridium botulinum. Therefore some method for controlling the germination of spores and their subsequent growth would be necessary to ensure a safe product over an extended storage period.A five strain cocktail of non-proteolytic C. botulinum was inoculated into raw chicken mince, which was cooked and then pressure treated at 600 MPa for 2 min at 20 °C. C. botulinum survived cooking and HPP and subsequently grew in the pressure-treated, cooked chicken during storage. Germination and growth was controlled when 2% w/w sodium lactate was added and when oxygen-permeable packaging was used. Weissella viridescens was not suitable for use as a protective culture to control the growth of C. botulinum. 相似文献
5.
《Food Control》2015
Current EC regulations require that ready-to-eat products should not exceed the limit of 100 CFU/g for Listeria monocytogenes throughout their shelf-life. On that basis a quantitative analysis for high hydrostatic pressure to produce safe (regarding L. monocytogenes levels) cured meat products with low salt concentration has been developed. An extended Doehlert design for a range of pressures (450–800 MPa), sodium chloride (0–34.9 g/L) and sodium nitrite (mg/L) concentrations, as well as the resulting aw (0.955–0.987) levels, was generated. Based on the logistic regression analysis, it appears that the recovery of L. monocytogenes is influenced by the applied pressure, the storage time and the synergistic effect of pressure and aw on inhibiting microbial recovery. This means that the sodium chloride and sodium nitrite concentrations tested indirectly affected the recovery of Listeria and consequently the shelf-life of the product by regulating the aw levels. The lower the water activity, the less the inactivation and recovery induced by pressure immediately and during storage, respectively. 相似文献
6.
《Food Control》2015
Bacteria can be injured or inactivated by high pressure processing (HPP), depending on the pressure level, holding time and bacterial strains and species. Fish soup was in this study treated with high pressure (400 and 600 MPa, 2 min) in combination with different packaging regimes; vacuum, modified atmosphere packaging (MAP), soluble gas stabilisation (SGS), and a combination of the two latter ones (SGS-MAP). The fish soup was before treatment inoculated with Listeria innocua, and stored at 5 °C and further analysed for a period up till 49 days. HPP gave a reduction of L. innocua of 3.5 and 7.3 log cfu/g immediately after exposure to 400 and 600 MPa, respectively. Both SGS and MAP showed a significant (P < 0.01) interaction with pressure. SGS in combination with pressure significantly (P < 0.001) inhibited the growth of L. innocua during storage. The same was observed when packaging in MAP (P < 0.001). Bacterial plating on non-selective and selective agar revealed that over 99.9% of the surviving cells after HPP treatment in combination with SGS or SGS-MAP were sublethally injured. 相似文献
7.
热管式搅拌轴在氧化反应釜上的应用 总被引：7，自引：0，他引：7
张红 《石油化工设备技术》1995,16(6):22-25
提出了将热管用作生产偏苯三酸装置中氧化反应釜搅拌轴的设计思想，阐述了其优越性和可行性，并对热管式搅拌轴进行了传热分析与强度计算，为该装置中氧化反应釜的设计提供了新思路。 相似文献
8.
介绍了低压合成甲醇催化剂(CuO-ZnO-Al_2O_3)预还原-钝化-再还原工艺的研究过程。预还原催化剂物化性能、使用寿命、催化活性和未经预还原的催化剂相同。生产上采用该工艺综合经济效益可达3％～10％。 相似文献
9.
《Food Control》2016
High pressure processing (HPP) is used on several types of seafood, though its potential for extending the shelf life of fresh fish has not been fully exploited. This study compared the effect of HPP (200 and 500 MPa, 120 s) on salmon, cod and mackerel. Immediately after processing, and during storage up to 26 days different analysis were carried out to evaluate the microbiological shelf life, oxidation, acid phosphatase level and pH of the different fish species during the storage period. For cod and mackerel, HPP at 500 MPa restrained the bacterial flora and it did not reach spoilage level, opposite to the salmon samples exposed to 500 MPa. Analysis of TBARS is often used as a measure of lipid oxidation. The TBARS-level was differently affected by pressure in salmon and cod. HPP at 200 MPa did not have any effect on the oxidation level in salmon during the storage period while this was observed for cod. The TBARS level in mackerel was high, independent of pressure treatment or not. Phosphatase activity in fish has been suggested to be related to freshness. The acid phosphatase (ACP) levels in control samples showed significant differences between salmon and cod. For salmon both control and samples treated at 200 MPa showed a decrease in ACP level at day 11 compared with day 0, whereas the HPP500 values were even throughout the study. This latter observation was also the case for cod treated at 500 MPa. This study have shown that HPP induce different levels of changes in various fish species. 相似文献
10.
《Food Control》2014
The individual and combined effects of high pressure carbon dioxide (HPCD) and nisin (200 IU/mL) on the inactivation of Escherichia coli O157:H7 suspended in physiological saline (PS, pH 5.60), phosphate-buffered saline (PBS, pH 5.60 or 7.00) or carrot juice (pH 6.80) were evaluated. The pressure in this study was 5 and 8 MPa, the temperature was 25 °C–45 °C, and the treatment time was 5–65 min. Inactivation of cells in PS (pH 5.60) by HPCD followed first order kinetics, the k (the inactivation rates) increased while the D (decimal reduction time) decreased in the presence of nisin, however, the acid solution dissolving nisin rather than nisin itself played a prominent role in this combination effect with HPCD in PS buffer. The inactivation kinetics of cells in PBS (pH 5.60 or 7.00) and carrot juice (pH 6.80) by HPCD followed slow-to-fast two-stage kinetics and was fitted by the modified Gompertz equation. The M (the time at which the absolute death rate is maximum) significantly decreased in the presence of nisin. HPCD enhanced the sensitization of E. coli to nisin and the time for the complete inactivation was shortened by 2.5–5 min in PBS buffer and carrot juice by combination of HPCD and nisin (HPCD + nisin) than by HPCD alone. Regression coefficients (R2) and mean square error (MSE) were used to evaluate the model performance, indicating that the models could provide a good fitting to the experimental data. 相似文献
11.
《Food Control》2017
This study combined plate counting method and fluorescent techniques (membrane integrity and potential, intracellular enzyme activity, and intracellular ROS level) to investigate the lethal and sublethal effects of slightly acidic electrolyzed water (SAEW) on Escherichia coli and Staphylococcus aureus. Also, the inactivation mechanism of SAEW was further explored through multiple cell targets (outer membrane and intracellular components). The results within 30 s SAEW treatment displayed 6.02 and 5.83 log reductions obtained for E. coli and S. aureus, respectively. The maximum sublethally injured cell proportions induced by SAEW exposure were 0.34 and 0.40 log10 CFU/mL for E. coli and S. aureus, respectively. According to the data from experiments of various acting cellular sites by fluorescent techniques, SAEW damaged the microbial membrane integrity and membrane potential severely. Also, it posed inactivation effect on the activity of intracellular esterase enzymes. Therefore, SAEW showed disinfection behavior with multiple cellular targets, including both cell barriers and intracellular components. Furthermore, SAEW did not result in accumulation of reactive oxygen species (ROS) inside microbial cell, indicating SAEW conducted a ROS-independent behavior on microbial inactivation and the chemical oxidants (e.g., hypochlorous acid) played major role in microbial intracellular oxidation processing. The result in this study will help to further understand the disinfection mechanism underlying SAEW on microorganisms and make SAEW inactivation targets more explicit. 相似文献
12.
《Food Control》2014
The aim of this study was to model the inactivation of Salmonella enterica serovar Enteritidis in pasteurized omelet internally inoculated at different microwave heating treatments (300 W; 450 W, 600 W and 800 W). Results indicated a non significant change in Salmonella populations during the first 30 s treatment at 300 W and 450 W, being log reductions lower than 0.5 log CFU g−1. However, after 40 s treatment, log reductions had risen to 4.8 log CFU g−1 at 800 W. Inactivation rates were higher at 600 W and 800 W (0.67 and 0.63 s−1) than at 300 W and 450 W (<0.34 s−1). The temperature-dependent parameters of a Weibull model obtained by Mattick, Legan, Humphrey & Peleg (2001) were evaluated. It was concluded that combinations characterized by a temperature equal or above 70 °C ensured a minimum 4 log reduction of Salmonella population (i.e. 300 W-80 s; 450 W-60 s or 600 W/800 W-40 s). These results may be of value in food service establishments, as target treatments for microwavable potato omelet portions. 相似文献
13.
《Food Control》2016
Atmospheric plasma provides the advantages of high microbial inactivation that can be performed under ambient conditions; therefore, it is regarded as a potential alternative to traditional food preservation methods. The present work presents the results of a critical study conducted on the efficiency of a non-thermal atmospheric pressure fluidized bed plasma (APFBP) system used for decontamination of maize. Maize grains that were artificially contaminated with Aspergillus flavus and Aspergillus parasiticus spores were treated in APFBP system for 1–5 min at two differently designed fluidized bed reactors with air and nitrogen. Results indicate maximum significant reductions of 5.48 and 5.20 log (cfu/g) in Aspergillus flavus and A. parasiticus after 5 min air plasma treatment. The native microbial flora of the maize grains decreased to more than 3 log after 3 min APFBP treatment, and no viable cells were counted. During the storage of plasma treated maize samples at 25 °C for 30 days, the Aspergillus spp. spores log reduction was maintained with no occurrence of re-growth. Overall, this study shows that plasma treatment has a fungicidal effect on A. flavus and A. parasiticus spores associated with alterations in spore surface morphology and loss of spore integrity. APFBP can inactivate aflatoxigenic spores on maize grains and could be optimized to improve the safety and quality of produce. 相似文献
14.
《Food Control》2015
The objective of this study was to develop artificial neural network (ANN) models for quantifying Escherichia coli O157:H7 (E. coli) inactivation due to low-voltage electric current on beef surfaces and to compare them with statistical models for their suitability as a tool for online processing by the meat industry. Modeling techniques with optimal prediction accuracies of E. coli inactivation on meat would not only enhance the meat quality and public perception from a safety perspective, but also improve the marketability of the meat products. The data used in this study were obtained from experiments that measured the percentage (%) of E. coli O157:H7 reduction (output) on beef surfaces when subjected to current (input 1) 300, 600, and 900 mA, duty cycles (input 2) 30, 50, and 70%, and frequency (input 3) 1, 10, and 100 kHz for three treatment times (2, 8, 16 min). Data were subjected to statistical and artificial neural network (ANN) modeling techniques. Data from each input set were sub-partitioned into training, testing, and validation data sets for ANN. Back-propagation (BP) and Kalman filter (KF) learning algorithms were used in ANN to develop nonparametric models between input and output data sets. The trained ANN models were cross-tested with validation data. Various statistical indices including R2 between actual and predicted outputs were produced and examined for selecting the best networks. Prediction plots for current, frequencies, and duty cycles indicated that ANN models had better accuracies compared to the statistical models in predicting from unseen pattern. Further, ANN models were able to more robustly generalize and interpolate unseen patterns within the domain of training. Since ANN models have the inherent ability to handle high biological variability and the uncertainty associated with inactivation of microorganisms, they have great potential for meat quality evaluation and monitoring in meat industry. 相似文献
15.
《Food Control》2015
In the present study, low-pressure glow discharge plasma was used for surface decontamination of the common food packaging materials, namely glass, polyethylene, polypropylene, nylon, and paper foil. Low-pressure air plasma was generated over a vacuum pressure range of 0.5–5.0 Torr, and at a power density range of 12.4–54.1 mW/cm3. Compared to plasma-unexposed surfaces, no significant changes in optical properties, color characteristics, surface temperatures, tensile strengths, and deformation strains were observed with plasma-exposed surfaces. On plasma exposure of food pathogens-loaded packaging materials surfaces, as high as 4-log reduction (99.99%) in viable cell counts of tested food pathogens, especially Escherichia coli O157:H7 and Staphylococcus aureus, was observed within 5 min. And, the pathogens inactivation pattern can be better explained by Singh-Heldman model. Therefore, low-pressure air plasma was shown to be effective for inactivation of major foodborne pathogens, and different food packaging materials can be decontaminated using the plasma without adversely affecting their physical properties. 相似文献
16.
采用黏土和聚乙烯醇按一定比例混合配制成复合黏结剂P-BN,以吉林桦甸粒径小于5 mm的小颗粒油页岩为原料,考察了成型工艺中黏结剂种类及加入量、水加入量、成型压力等条件对成型油页岩抗碎强度及热稳定性的影响。结果表明,适宜的成型条件为复合黏结剂P-BN加入量(占原料的质量分数)0.30%,水加入量20%,成型压力30 MPa;在上述优选条件下所制备成型油页岩的低温铝甑干馏出油率为12.03%,半焦收率为76.09%。 相似文献
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20.
《Food Control》2017
Sprout-related outbreaks of foodborne illnesses are increasingly becoming a food safety concern. Different pathogenic microorganisms that originate from sprout seeds are known to play a crucial role in the pathogenesis of such outbreaks. Therefore, in order to decontaminate and also to enhance the germination of seeds, the applications of non-thermal plasma based techniques are increasingly being investigated in the field of agricultural science as an alternative to conventional pre-germination treatments. This work was aimed to evaluate the effectiveness of corona discharge plasma jet (CDPJ) for microbial decontamination of rapeseed seeds, and also studied the plasma treatment effect on the seed germination and physicochemical properties of sprouts (grown from the plasma-treated seeds). Aerobic bacteria, molds and yeast, Bacillus cereus, Escherichia coli, Salmonella spp. were detected as contaminants in the seeds. All the detected microorganisms were reduced in the range of 1.2–2.2 log CFU/g upon the CDPJ treatment for 3 min. The inactivation patterns are better explained using pseudo-first-order kinetics. The plasma treatment of seeds up to 2 min showed positive effects on their germination rate and seedling growth. Physicochemical and sensory characteristics of rape sprouts were unaffected due to the CDPJ treatment of their respective seeds. Therefore, the CDPJ treatment of rapeseed seeds has not only reduced the seed microbial load, but also contributed to the enhancement of their germination rate and seedling growth, without adversely affecting the physicochemical and sensory characteristics of their corresponding sprouts. 相似文献