D-value

D 值
  • 文章类型: Journal Article
    爱知病毒(AiV)在全球范围内导致胃肠炎,通过受污染的贝类和水传播。AiV对常见灭活过程的抗性/耐受性以及缺乏市售疫苗使得有必要研究其热灭活动力学。这项研究通过线性和Weibull模型使用2ml无菌玻璃小瓶评估了AiV在细胞培养基中的热灭活。在50、54和58°C的水浴中进行三次AiV滴度为7个对数菌斑形成单位(PFU)/ml的热处理,最长90分钟。每个稀释的一式两份的空斑测定用于确定感染性病毒滴度。AiV在50±1°C时的线性模型D值(±=标准误差)(出现时间=68s),54±0.7°C(130s),58±0.6°C(251s)为43.3±4.23(R2=0.40,RMSE=0.56),5.69±0.28(R2=0.80,RMSE=0.43),和1.20±0.63分钟(R2=0.69,RMSE=0.39),分别,线性模型z值为5.14±0.39°C(R2=0.99,RMSE=0.08)。对于相同的温度,Weibull模型td=1值为20.98±8.8(R2=0.62,RMSE=0.46,α(尺度参数)=2.30,β(形状参数)=0.38),3.84±0.69(R2=0.85,RMSE=0.38,α=1.08,β=0.66),0.87±0.10min(R2=0.80,RMSE=0.32,α=0.22,β=0.61),分别为z值(使用Td=1)为5.79±0.22°C(R2=1.0,RMSE=0.03)。对于具有较高R2和较低RMSE值的对数减少对时间的Weibull模型获得了更好的拟合。AiV灭活参数的应用有助于降低AiV爆发的风险。
    Aichi virus (AiV) that results in gastroenteritis worldwide, is spread through contaminated shellfish and water. The resistance/tolerance of AiV to common inactivation processes along with the absence of commercially available vaccines makes it necessary to study its thermal inactivation kinetics. This research evaluated the heat inactivation of AiV in cell-culture media using 2-ml sterile glass vials by the linear and Weibull models. Heat treatments of AiV titers of 7 log plaque forming units (PFU)/ml were conducted thrice in a water-bath at 50, 54, and 58 °C for up to 90 min. Plaque assays for each dilution in duplicate were used to determine infectious virus titers. Linear model D-values for AiV at 50 ± 1 °C (± = standard error) (come-up time = 68 s), 54 ± 0.7 °C (130 s), and 58 ± 0.6°C (251 s) were 43.3 ± 4.23 (R2 = 0.40, RMSE = 0.56), 5.69 ± 0.28 (R2 = 0.80, RMSE = 0.43), and 1.20 ± 0.63 min (R2 = 0.69, RMSE = 0.39), respectively, and the linear model z-value was 5.14 ± 0.39°C (R2 = 0.99, RMSE = 0.08). For the same temperatures, the Weibull model td = 1 values were 20.98 ± 8.8 (R2 = 0.62, RMSE = 0.46, α (scale parameter) = 2.30, β (shape parameter) = 0.38), 3.84 ± 0.69 (R2 = 0.85, RMSE = 0.38, α = 1.08, β = 0.66), and 0.87 ± 0.10 min (R2 = 0.80, RMSE = 0.32, α = 0.22, β = 0.61), respectively and the z-value (using Td = 1 ) was 5.79 ± 0.22 °C (R2 = 1.0, RMSE = 0.03). A better fit was obtained with the Weibull model for log reductions versus time with higher R2 and lower RMSE values. Application of AiV inactivation parameters can help reduce the risk of AiV outbreaks.
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  • 文章类型: Journal Article
    Ethyl(dimethyl)(tetradecyl)ammonium ethyl sulfate, used in laundry detergents, shampoos, and body soaps, is classified by the Japanese Chemical Substances Control Law as a priority assessment chemical substance for environmental effects. However, its toxicity data for human health are insufficient. This study evaluated this chemical under the Safety Examination of Existing Chemicals and Safety Programmes of the Ministry of Health, Labour and Welfare (MHLW). The MHLW conducted bacterial reverse mutation (Ames test), in vitro chromosomal aberration, and combined repeated-dose and reproductive/developmental toxicity screening tests. We performed a screening assessment of ethyl(dimethyl)(tetradecyl)ammonium ethyl sulfate for human health. The chemical showed a negative reaction in the Ames test and a positive reaction in the in vitro chromosomal aberration test with metabolic activation in rats. The combined repeated-dose and reproductive/developmental toxicity screening test showed significantly decreased food consumption at 50 mg/kg body weight/day, but no reproductive and developmental toxicity was observed. The no-observed-effect level of 15 mg/kg/day was obtained as a screening value. Therefore, this chemical was classified as hazard class 3, with a derived-no-effect level of 0.025 mg/kg/day. The results of this study will be useful for risk assessment of groups of structurally similar alkyl quaternary ammonium surfactants.
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  • 文章类型: Journal Article
    Animal intestines are the source of edible sausage casings, which are traded worldwide and may come from areas where notifiable infectious animal diseases are prevalent. To estimate the risks of virus contamination, knowledge about the quantity of virus and decimal reduction values of the standard preservation method by salting is of great importance. A literature search, based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, was performed in search engine CAB Abstracts to determine the viral load of 14 relevant animal viruses in natural casings or intestines. Only a very limited number of scientific publications per virus were found and viral loads in the intestines varied from high for ASFV (five publications), BVDV (3), CSFV (6), PPRV (3), RPV(2) and TGEV (3) to moderate for PEDV (2) and SVDV (3), low for HEV (2) and FMDV (5), very low for VESV (1) and negative for PrV (2) and VSV (1). PRRSV was found in intestines, however, viral titers were not published. Three viruses (BVDV, CSFV and PPRV) with high viral loads were selected to search for their inactivation kinetics. For casings, no inactivation data were found, however, thermal inactivation data of these viruses were available, but differed in quantity, quality and matrices. In conclusion, important data gaps still exist when it comes to the quantitative inactivation of viruses in sausage casings or livestock intestines.
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  • 文章类型: Journal Article
    MozzarelladiBufalaCampana受保护的原产地奶酪中单核细胞增生李斯特菌的存在可能取决于凝乳的拉伸条件和包装前的污染。为了避免交叉污染,水的热处理,盐水和覆盖液体可能变得必要。本研究旨在提高有关单核细胞增生李斯特菌耐热性的知识,重点是某些奶酪制作操作的影响,即成型后与奶酪接触的凝乳拉伸和热处理,为了提高奶酪的安全性,优化流程的有效性和可持续性。此外,讨论了奶酪凝乳在单核细胞增生李斯特菌失活中的作用。在60°C下8分钟后,12个测试菌株显示出非常不均匀的耐热性,其降低范围为7至小于1Log10cfu/mL。在60和70°C之间计算出的最耐热应变的D值(十进制减少时间)和z值(热阻常数)受矩阵的影响很大,特别是,排干奶酪凝乳的耐热性明显增加。因为奶酪凝乳拉伸不是等温过程,为了模拟工业过程的整体致死效应,建立了二级模型。估计该过程的致死效应约为4Log10减少。所提供的数据可能对新鲜的意大利面filata奶酪生产商确定适当的加工持续时间和温度以生产安全的奶酪很有用。
    The presence of Listeria monocytogenes in Mozzarella di Bufala Campana Protected Designation of Origin cheeses may depend on curd stretching conditions and post contaminations before packaging. To avoid cross-contamination, thermal treatment of water, brines and covering liquid may become necessary. The present study aimed to improve knowledge about L. monocytogenes thermal resistance focusing on the influence of some cheese making operations, namely curd stretching and heat treatment of fluids in contact with cheese after molding, in order to improve the safety of the cheese, optimize efficacy and sustainability of the processes. Moreover, the role that cheese curd stretching plays in L. monocytogenes inactivation was discussed. The 12 tested strains showed a very heterogeneous heat resistance that ranged from 7 to less than 1 Log10 Cfu/mL reduction after 8 min at 60°C. D-values (decimal reduction times) and z-values (thermal resistance constant) calculated for the most heat resistant strain among 60 and 70°C were highly affected by the matrix and, in particular, heat resistance noticeably increased in drained cheese curd. As cheese curd stretching is not an isothermal process, to simulate the overall lethal effect of an industrial process a secondary model was built. The lethal effect of the process was estimated around 4 Log10 reductions. The data provided may be useful for fresh pasta filata cheese producers in determining appropriate processing durations and temperatures for producing safe cheeses.
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  • 文章类型: Journal Article
    Personalized medicine asks if a new treatment will help a particular patient, rather than if it improves the average response in a population. Without a causal model to distinguish these questions, interpretational mistakes arise. These mistakes are seen in an article by Demidenko [2016] that recommends the \"D-value,\" which is the probability that a randomly chosen person from the new-treatment group has a higher value for the outcome than a randomly chosen person from the control-treatment group. The abstract states \"The D-value has a clear interpretation as the proportion of patients who get worse after the treatment\" with similar assertions appearing later. We show these statements are incorrect because they require assumptions about the potential outcomes which are neither testable in randomized experiments nor plausible in general. The D-value will not equal the proportion of patients who get worse after treatment if (as expected) those outcomes are correlated. Independence of potential outcomes is unrealistic and eliminates any personalized treatment effects; with dependence, the D-value can even imply treatment is better than control even though most patients are harmed by the treatment. Thus, D-values are misleading for personalized medicine. To prevent misunderstandings, we advise incorporating causal models into basic statistics education.
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  • 文章类型: Journal Article
    To ensure safe reuse, biosolids are stabilized to reduce pathogens, odor, and volatile solids. Stabilization by lime addition have high material costs, high transportation costs, and loss of ammonia. Decreasing required lime additions would improve the sustainability of biosolids reuse. This study examined combining lime and heat treatment to reduce lime additions needed for required fecal coliform destruction. In contrast to the current best management practice requiring a pH of 12, fecal coliform reduction for final concentrations <1000 MPN/g (where MPN is most probable number) was achieved with pH as low as 10 when combined with a short (1-h) incubation at 60 °C. Analysis of D-values (the time required to destroy 1-log fecal coliform) supported a synergistic treatment response at moderate pH and heat treatments. Samples receiving higher temperature treatments had lower specific oxygen uptake rates, suggesting that readily-available carbon was lost during heat treatment. Samples with lower lime additions had higher final ammonia concentrations, which is a desired characteristic for biosolids reclaimed as a fertilizer. The study demonstrated that optimizing combined lime and heat stabilization can improve beneficial reuse as a means toward enhancing environmental sustainability and improving the circular economy.
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  • 文章类型: Journal Article
    耐热模具(HRMs)的管理被认为是果汁水果行业的巨大挑战。Neosartorya,Bysochlamys和Talaromyces是从果汁中分离出的三个主要属,它们对热处理具有很强的抵抗力。在文献中可以找到几个失活参数,然而,所有这些都是在特定的食物基质中进行的,并使用不同的灭活方法。因此,这项荟萃分析研究通过调整扩展的基于Bigelow的荟萃回归模型,根据在不同液体培养基中进行的灭活实验数据,综合了3种HRM的热阻参数.荟萃分析数据,从1969年至2017年的出版物中提取,由十进制减少时间(D)组成,失活方法,失活温度,pH值,°白利糖度,孢子的年龄,和介质类型(型号,果汁,concentrations).集合D*值(D在90°C,pH3.5和12°白利糖度)估计为B.fulva(1.95分钟;95%CI:1.21-3.11分钟),Talaromyces(4.03分钟;95%CI:3.43-4.74分钟),Neosardorya(0.5.35分钟;95%CI:4.10-7.08分钟),和B.nivea(10.32分钟;95%CI:5.81-18.4分钟)。已发现,与增加模型液体或果汁中的可溶性固体相比,增加浓缩物中的可溶性固体往往会导致Neosardorya和Talaromyces的耐热性降低较低(p=0.001;0.012)。总的来说,螺旋盖管和三颈圆形灭活方法比热死亡管呈现更高的D*值(p<0.05),聚乙烯袋和毛细管法。Talaromyces的孢子(总体zpH=7.56;95%CI:5.13-13.5)和Neosartorya的孢子(总体zpH=7.07;95%CI:5.04-10.8)似乎对培养基pH的降低更热敏感比Byssochlamys的孢子(总体zpH=4.34;95%CI:3.20-6.73)。这项研究中提出的元回归模型对于估计果汁行业在热处理管理和确定保质期中使用的合并失活动力学参数非常有价值。
    The management of Heat Resistant Moulds (HRMs) is considered a great challenge for the juice fruit industry. Neosartorya, Byssochlamys and Talaromyces are three out of the main genera isolated from fruit juices that show great resistance to heat treatments. Several inactivation parameters can be found in the literature, however all of them were carried out in specific food matrices and using diverse inactivation methods. Thus, this meta-analysis study synthesizes the thermal resistance parameters of the three HRMs by adjusting extended Bigelow-based meta-regression models to data on inactivation experiments conducted in different liquid media. The meta-analytical data, extracted from publications between 1969 and 2017, was composed of decimal reduction time (D), inactivation method, temperature of inactivation, pH, °Brix, age of spores, and type of medium (model, juice, concentrates). Pooled D* values (D at 90 °C, pH 3.5 and 12° Brix) were estimated for B. fulva (1.95 min; 95% CI: 1.21-3.11 min), Talaromyces (4.03 min; 95% CI: 3.43-4.74 min), Neosartorya (0.5.35 min; 95% CI: 4.10-7.08 min), and B. nivea (10.32 min; 95% CI: 5.81-18.4 min). It was found that increasing the soluble solids in concentrates tends to cause a lower decrease in the heat resistance of Neosartorya and Talaromyces than increasing the soluble solids in model liquid or juices (p = 0.001; 0.012). In general, the screw-capped tubes and three neck round inactivation methods render higher D* values (p < 0.05) than the thermal death tubes, the polyethylene bag and the capillary methods. Spores of Talaromyces (overall zpH = 7.56; 95% CI: 5.13-13.5) and Neosartorya (overall zpH = 7.07; 95% CI: 5.04-10.8) appear to be more thermal sensitive to a decrease in medium pH than spores of Byssochlamys (overall zpH = 4.34; 95% CI: 3.20-6.73). The meta-regression models presented in this study can be valuable for estimating pooled inactivation kinetic parameters to be used by the fruit juice industry in the management of thermal processes and in the determination of shelf-life.
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  • 文章类型: Journal Article
    Egg powders are increasingly popular ingredients, due to their functionality and compactness, in industrial food production and preparation at homes. However, there is a lack of studies that evaluate the thermal resistance of Salmonella Enteritidis PT30 and its potential surrogate Enterococcus faecium NRRL B-2354 in egg powders. This study examined the log-linear relationship between the thermal resistance of Salmonella Enteritidis (D-value) and the water activity (aw) of egg powders. The changes of aw in the egg powders with temperature were measured using a Vapor Sorption Analyzer and a high-temperature cell. The D80 ℃-value of S. Enteritidis PT30 and E. faecium inoculated in the egg powders preconditioned to three aw levels (0.3, 0.45, and 0.6) at 20 ℃ were determined using aluminum thermal death test cells. The aw values increased (P < 0.05) in all three egg powders when the temperature of the samples was raised from room temperature to 80 ℃. The D80 ℃-values ranged from 5.3 ± 0.1 to 25.9 ± 0.2 min for S. Enteritidis while 10.4 ± 0.4 to 43.8 ± 0.4 for E. faecium in samples of the three different aw levels. S. Enteritidis PT30 showed a log-linear relationship between D80 ℃-values and aw80 ℃ for the egg powders. This study contributes to our understanding of the impact of aw on the development of thermal treatments for low-moisture foods.
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  • 文章类型: Journal Article
    This study investigated the effects of sous vide cooking at temperatures between 50 °C and 60 °C on the inactivation kinetics of Listeria (L.) monocytogenes. Nutrient broth and minced game meat (Capreolus capreolus and Sus scrofa) were inoculated with three strains of L. monocytogenes and cooked under sous vide conditions (50, 55 or 60 °C for several hours). Results showed that the decimal reduction values (D-values) were largely dependent on the surrounding matrix. D-values of 125.5, 29.7 and 5.1 min were reached for BHI (brain heart infusion) at 50 °C, 55 °C and 60 °C, respectively. For roe deer, D-values of 49.2, 14.9 and 3.7 min and for wild boar, D-values of 100.2, 23.8 and 4.2 min were reached. It can be concluded that microbiologically safe cooking durations under sous-vide conditions below 60 °C should be considered individually for each meat product due to the dramatic influence of the matrix in comparison to higher temperature conditions.
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  • 文章类型: Journal Article
    Staphylococcus aureus is a significant opportunistic pathogen in humans, dairy cattle, and camels. The presence of antibiotic-resistant and heat-resistant bacteria in camel milk has become a potential public health issue. The phenotypic and molecular characterization of methicillin-resistant staphylococcal strains recovered from pasteurized camel milk distributed in retail markets of Saudi Arabia was assessed. A total of 100 samples were collected between March and May 2017. Out of the 20 S. aureus isolates that were recovered from the pasteurized camel milk, 10 were found to be resistant to cefoxitin (30 µg) and, thus, were designated as methicillin-resistant strains. The resistance ratio of methicillin-resistant S. aureus isolates for a different class of antibiotics was determined by performing the antimicrobial susceptibility test and was estimated to be approximately 60%. Polymerase chain reaction assay was performed to amplify the methicillin-resistant gene mecA, and furthermore, nucleotide sequencing was performed to detect and verify the presence of methicillin-resistant strains. Upon sequencing the putative S. aureus methicillin-resistant strains, we obtained 96 to 100% similarity to the penicillin-binding protein 2a gene (mecA) of the S. aureus strain CS100. Moreover, the 10 methicillin-resistant S. aureus isolates were also identified to be heat resistant and were stable at temperatures up to 85°C for 60 s, with 3 isolates being heat resistant even at 90°C for 60 or 90 s. The mean decimal reduction time (D85 value) was 111 s for all the 10 isolates. No difference was observed in the profile of total protein between the 10 methicillin- and heat-resistant S. aureus isolates and the S. aureus strain ATCC 29737, which was determined by sodium dodecyl sulfate-PAGE analyses. Therefore, we could conclude that a relatively high percentage of the tested pasteurized camel milk samples were contaminated with S. aureus (20%) and methicillin- and heat-resistant S. aureus (10%).
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