Inactivation of hepatitis A virus and norovirus surrogate in suspension and on food-contact surfaces using pulsed UV light (pulsed light inactivation of food-borne viruses)

This study was conducted to evaluate the inactivation of murine norovirus (MNV-1) and hepatitis A virus (HAV) by pulsed ultraviolet (UV) light. MNV-1 was used as a model for human norovirus. Viral suspensions of about 10⁶ PFU/ml were exposed to pulses of UV light for different times and at different distances in a Xenon Steripulse device (model RS-3000C). Inactivation studies were also carried out on 1-cm² stainless steel and polyvinyl chloride disks with 10⁵ PFU/ml. Inactivation of MNV-1 and HAV at 10.5 cm from the UV source was greater on inert surfaces than in suspension. The presence of organic matter (fetal bovine serum) reduced the effectiveness of pulsed light both in suspension and on surfaces. However, 2-s treatment in the absence of FBS completely inactivated (5 log reduction) the viral load at different distances tested, whether in suspension (MNV-1) or on disks (MNV-1 and HAV). The same treatment in the presence of fetal bovine serum (5%) allowed a reduction of about 3 log. This study showed that short duration pulses represent an excellent alternative for inactivation of food-borne viruses. This technology could be used to inactivate viruses in drinking water or on food-handling surfaces.     

Thermal inactivation of foot-and-mouth disease virus in milk using high-temperature, short-time pasteurization

Previous studies of laboratory simulation of high temperature, short time pasteurization (HTST) to eliminate foot-and-mouth disease virus (FMDV) in milk have shown that the virus is not completely inactivated at the legal pasteurization minimum (71.7°C/15 s) but is inactivated in a flow apparatus at 148°C with holding times of 2 to 3 s. It was the intent of this study to determine whether HTST pasteurization conducted in a continuous-flow pasteurizer that simulates commercial operation would enhance FMDV inactivation in milk. Cows were inoculated in the mammary gland with the field strain of FMDV (01/UK). Infected raw whole milk and 2% milk were then pasteurized using an Arm-field pilot-scale, continuous-flow HTST pasteurizer equipped with a plate-and-frame heat exchanger and a holding tube. The milk samples, containing FMDV at levels of up to 10⁴ plaque-forming units/mL, were pasteurized at temperatures ranging from 72 to 95°C at holding times of either 18.6 or 36 s. Pasteurization decreased virus infectivity by 4 log₁₀ to undetectable levels in tissue culture. However, residual infectivity was still detectable for selected pasteurized milk samples, as shown by intramuscular and intradermal inoculation of milk into naïve steers. Although HTST pasteurization did not completely inactivate viral infectivity in whole and 2% milk, possibly because a fraction of the virus was protected by the milk fat and the casein proteins, it greatly reduced the risk of natural transmission of FMDV by milk.     

Inactivation and degradation of O Taiwan97 foot-and-mouth disease virus in pork sausage processing

This study was to investigate the levels of inactivation and degradation of a field-isolated foot-and-mouth disease virus (FMDV)-strain O Taiwan97 in pork sausage processing. FMDV antibody-free pigs were inoculated with virus suspensions and slaughtered after developing observable symptoms. Lymph nodes (LN), blood clots (BC), and muscle were collected for the evaluation of inactivation during chilling, curing, drying and steaming processes. Viable virus was assessed by the TCID₅₀ technique and RT-PCR was used to detect viral genomes. Cell culture results revealed that viruses could be detected from LN and BC, but not from muscle. Ninety percent of FMDV was inactivated after each of the chilling, curing and steaming processes as compared to <80% inactivation after the drying process. The FMDV genome was detectable in 88% of the muscle, and was found in 100% of the serum, BC and LN. After processing, a majority of the genomes were not degraded more than 60%, with the exception of the thermal-steaming process. These findings indicated that the FMDV genome was detectable after each processing step, indicating a potential infectious risk. Thus, apart from regular surveillance in the field, monitoring of meat product pH and heat treatments are essential for FMDV inactivation.     

Thermal inactivation of hepatitis A virus in suspension and in dried mussels (Mytilus edulis)

We examined the effects of three different temperatures (60, 85 and 100 °C) and durations of time (1 min at 100  ° C to 30 min at 60  ° C) on hepatitis A virus (HAV) in suspension and dried mussels (Mytilus edulis). In suspension, 3.61, 4.48, 5.06 and 5.66 log₁₀ tissue culture infectious dose (TCID)₅₀/mL were reduced by 60  ° C for 5 min, 60  ° C for 15 min, 60  ° C for 30 min and 85  ° C for 3 min, respectively. In dried mussels, 1.34, 1.94, 3.16, 2.36, 3.53 and 4.38 log₁₀TCID₅₀/mL were reduced by 60  ° C for 5 min, 60  ° C for 15 min, 60  ° C for 30 min, 85  ° C for 3 min, 85  ° C for 6 min and 85  ° C for 10 min, respectively. HAV inactivation from suspension and dried mussels was achieved by 85  ° C for 6 min and 15 min, respectively, and also by a 1 min at 100  ° C. At 60, 85 and 100  ° C, the 1‐log (D‐values) inactivation from both suspension and dried mussels was 6.33 and 7.93, 0.98 and 3.05, and 0.28 and 0.38 min, respectively. A higher temperature and/or a thermal treatment time shorter than 85  ° C for 6 min (100  ° C for 1 min) could be used for commercial target foods for complete HAV inactivation.     

Isolation and characterization of barosensitive mutants of Saccharomyces cerevisiae obtained by UV mutagenesis

Using UV mutagenesis, 2 high-pressure (HP) sensitive (barosensitive) mutants of Saccharomyces cerevisiae were obtained. The HP inactivation of the mutants, as well as their parent strains, followed 1st-order kinetics in the range of 175 to 250 MPa within 600 s. Both mutants showed larger 1st-order inactivation rate constant values or significant loss of viabilities, compared with their parent strains in the pressure range tested. The inactivation rate constant value of one of the mutants was comparable with that of a previously reported highly barosensitive strain, which was generated by deletion of hsp104 in a trehalose deficient strain. The activation volume values of HP inactivation reactions in the 2 mutants were apparently equivalent with those of their parent strains. This suggested that the mutation did not bring drastic volume changes of the key molecules for HP inactivation. Their auxotrophic properties, growth, and ethanol fermentation were identical in mutant and parent strains. The mutants could therefore be useful for fermentations where control by HP processing is desired.     

Pulsed light for the inactivation of fungal biofilms of clinically important pathogenic Candida species

Microorganisms are naturally found as biofilm communities more than planktonic free‐floating cells; however, planktonic culture remains the current model for microbiological studies, such as disinfection techniques. The presence of fungal biofilms in the clinical setting has a negative impact on patient mortality, as Candida biofilms have proved to be resistant to biocides in numerous in vitro studies; however, there is limited information on the effect of pulsed light on sessile communities. Here we report on the use of pulsed UV light for the effective inactivation of clinically relevant Candida species. Fungal biofilms were grown by use of a CDC reactor on clinically relevant surfaces. Following a maximal 72 h formation period, the densely populated biofilms were exposed to pulsed light at varying fluences to determine biofilm sensitivity to pulsed‐light inactivation. The results were then compared to planktonic cell inactivation. High levels of inactivation of C. albicans and C. parapsilosis biofilms were achieved with pulsed light for both 48 and 72 h biofilm structures. The findings suggest that pulsed light has the potential to provide a means of surface decontamination, subsequently reducing the risk of infection to patients. The research described herein deals with an important aspect of disease prevention and public health.     

Ultraviolet inactivation kinetics of Escherichia coli and Yersinia pseudotuberculosis in annular reactors

Terrorist threats have precipitated the need for information on the ultraviolet (UV) resistance of potential biothreat agents in food processing, such as Yersinia pestis. The objective of this study was to characterize the resistance of the Yersinia species to UV treatment using a single-lamp annular UV reactor. A novel method is proposed to measure the inactivation kinetics of Yersinia pseudotuberculosis, a surrogate of Y. pestis. This proposed method can overcome the disadvantages of the traditional collimated beam approach for liquids with high absorptive properties, such as liquid foods. As a reference, an inactivation rate of Escherichia coli K12 in caramel model solutions was measured first. Both first-order and series-event inactivation models were used to fit UV inactivation data. For the series-event model, an inactivation constant of k(SE)= 0.675 cm(2)/mJ and threshold n= 4 were obtained for E. coli K12 with the coefficient of determination R(2)= 0.987 and the standard deviation of log(10) reductions sigma(y)= 0.133. For Y. pseudotuberculosis, k(SE)= 0.984 cm(2)/mJ and n= 3 were obtained with R(2)= 0.972 and sigma(y)= 0.212. In contrast, for the first-order inactivation model, the first-order inactivation constant k(1)= 0.325 cm(2)/mJ with R(2)= 0.907 and sigma(y)= 0.354 was found for E. coli; and k(1)= 0.557 cm(2)/mJ with R(2)= 0.916 and sigma(y)= 0.402 was obtained for Y. pseudotuberculosis. Based on R(2), sigma(y), and the maximum absolute and relative errors, the series-event inactivation model describes the UV inactivation kinetics of Y. pseudotuberculosis and E. coli better than the first-order model. It is apparent that Y. pseudotuberculosis is less resistant to UV light than E. coli K12.     

Ultraviolet radiation as a non-thermal treatment for the inactivation of microorganisms in fruit juice

Fruit juices can be processed using ultraviolet (UV-C) light to reduce the number of microorganisms. The UV-C wavelength of 254 nm is used for the disinfection and has a germicidal effect against microorganisms. A novel turbulent flow system was used for the treatment of apple juice, guava-and-pineapple juice, mango nectar, strawberry nectar and two different orange and tropical juices. In comparison to heat pasteurization, juices treated with UV did not change taste and color profiles. Ultraviolet dosage levels (J L^− 1) of 0, 230, 459, 689, 918, 1 148, 1 377, 1 607 and 2 066 were applied to the different juice products in order to reduce the microbial load to acceptable levels. UV-C radiation was successfully applied to reduce the microbial load in the different single strength fruit juices and nectars but optimization is essential for each juice treated. This novel UV technology could be an alternative technology, instead of thermal treatment or application of antimicrobial compounds.

Industrial relevance

This novel UV-C system can be applied successfully to the Food Industry. UV-C can be effectively used to reduce the number of spoilage and pathogenic bacteria, as well as yeasts and moulds in different kinds of fruit juices.     

二氧化氯对苹果表面Listeria monocytogenes杀菌效果的研究

利用A PI Listeria鉴定系统对从榨汁苹果表面分离的Listeria monocytogenes疑似菌落进行了鉴定,并将原料清洗与杀菌过程相结合,通过4因素中心组合试验设计(CCD),以杀菌效果(以杀菌效率的负对数表示,即logNN )为响应值,研究二氧化氯溶液浓度、杀菌温度、处理时间和杀菌液pH 等因素对杀 0菌效果的影响,用数学方法描述二氧化氯对苹果表面Listeria m onocytogenes的杀菌规律。结果表明:二氧化氯浓度对杀菌效果影响最大,杀菌液pH 次之,杀菌温度影响最小,延长杀菌时间对杀菌效果的影响不显著,二氧化氯溶液浓度、杀菌温度和pH 之间对杀菌效果有协同作用,建立的数学模型其预报结果与实测结果拟合基本一致,相对误差在 5.0% 以内。 ±     

Virus inactivation by salt (NaCl) and phosphate supplemented salt in a 3D collagen matrix model for natural sausage casings

Due to possible presence and spread of contagious animal viruses via natural sausage casings the international trade in these food products is subject to veterinary and public health requirements. In order to manage these restrictions we determined the effect of casing preservation on four highly contagious viruses for livestock: foot-and-mouth-disease virus (FMDV), classical swine fever virus (CSFV), swine vesicular disease virus (SVDV) and African swine fever virus (ASFV). We used an in vitro 3D collagen matrix model in which cells, infected with the four different viruses were embedded in a bovine collagen type I gel matrix and treated with either saturated salt (NaCl) or phosphate supplemented saturated salt at four different temperatures (4, 12, 20 and 25 °C) during a period of 30 days. The results showed that all viruses were faster inactivated at higher temperatures, but that stability of the various viruses at 4 °C differed. Inactivation of FMDV in the 3D collagen matrix model showed a clear temperature and treatment effect on the reduction of FMDV titres. At 4 and 12 °C phosphate supplemented salt showed a very strong FMDV inactivation during the first hour of incubation. Salt (NaCl) only had a minor effect on FMDV inactivation. Phosphate supplemented salt treatment increased the effect temperature had on inactivation of CSFV. In contrast, the salt (NaCl) treatment only increased CSFV inactivation at the higher temperatures (20 °C and 25 °C). Also SVDV inactivation was increased by phosphate supplemented salt, but salt (NaCl) treatment only resulted in a significant decrease of SVDV titre at a few time points. The ASFV results showed that both salt (NaCl) and phosphate supplemented salt were capable to inactivate ASFV within 48 h. In contrast to the other viruses (FMDV, CSFV and SVDV), ASFV was the most stable virus even at higher temperatures. The results obtained in this in vitro model underline the efficacy of a combined treatment using phosphate supplemented salt and storage at 20 °C or higher for a period of 30 days. This treatment may therefore be useful in reducing the animal health risks posed by spread of contagious animal viruses by international trade of natural sausage casings.     

Thermal inactivation of avian influenza and Newcastle disease viruses in chicken meat

Avian influenza viruses (AIV) and Newcastle disease viruses (NDV) of high pathogenicity cause severe systemic disease with high mortality in chickens and can be isolated from the meat of infected chickens. Although AIV and NDV strains of low pathogenicity are typically not present in chicken meat, virus particles in respiratory secretions or feces are possible sources of carcass contamination. Because spread of AIV and NDV is associated with movement of infected birds or their products, the presence of these viruses in chicken meat is cause for concern. This study presents thermal inactivation data for two viruses of high pathogenicity in chickens (AIV strain A/chicken/Pennsylvania/1370/1983 and NDV strain APMV-1/ chicken/California/S0212676/2002) and two viruses of low pathogenicity in chickens (AIV strain A/chicken/Texas/298313/ 2004 and NDV strain APMV-1/chicken/Northern Ireland/Ulster/1967). Under the conditions of the assay, high-pathogenicity AIV was inactivated more slowly in meat from naturally infected chickens than in artificially infected chicken meat with a similar virus titer. In contrast, high-pathogenicity NDV was inactivated similarly in naturally and artificially infected meat. Linear regression models predicted that the current U.S. Department of Agriculture-Food Safety and Inspection Service time-temperature guidelines for cooking chicken meat to achieve a 7-log reduction of Salmonella also would effectively inactivate the AIV and NDV strains tested. Experimentally, the AIV and NDV strains used in this study (and the previously studied H5N1 high-pathogenicity AIV strain A/chicken/Korea/ES/2003) were effectively inactivated in chicken meat held at 70 or 73.9 degrees C for less than 1 s.     

猕猴桃浆欧姆加热特性及酶失活率数学模型的建立

利用欧姆加热技术对猕猴桃浆进行加热,探讨了加热过程中加热速率和电导率的变化规律,建立了多酚氧化酶和过氧化物酶失活率的数学模型。结果表明,加热速率随着电场强度的升高而增大,电场强度对试样的电导率影响不大,随着温度的升高,电导率呈线性关系增大;回归方程在α=0.05水平显著,可用于欧姆加热工艺参数对多酚氧化酶和过氧化物失活影响的预测。研究结果可为猕猴桃浆的深加工提供理论基础。     

微波加热对三种微生物致死的Weibull模型

探讨不同微波功率加热至不同温度下对沙门氏菌、大肠杆菌和金黄色葡萄球菌等三种对象菌的致死作用,运用Weibull模型描述其致死历程,由Weibull模型计算微波加热使微生物数量减少5-log所需要的时间,并验证其模型的精确度。结果表明,Weibull模型描述沙门氏菌、大肠杆菌和金黄色葡萄球菌的致死历程均有较高的拟合度,通过Weibull模型推算出来的沙门氏菌、大肠杆菌和金黄色葡萄球菌减少5-log的时间与实验结果相近。     

Thermal and chemical inactivation of Lactobacillus virulent bacteriophage

The effect of thermal treatments and several biocides on the viability of Lactobacillus virulent phage P1 was evaluated. Times to achieve 99% inactivation (T₉₉) of phage at different treatment conditions were calculated. The thermal treatments applied were 63, 72, and 90°C in 3 suspension media (de Man, Rogosa, Sharpe broth, reconstituted skim milk, and Tris magnesium gelatin buffer). Phage P1 was completely inactivated in 5 and 10 min at 90 and 72°C, respectively; however, reconstituted skim milk provided better thermal protection at 63°C. When phage P1 was treated with various biocides, 800 mg/L of sodium hypochlorite was required for total inactivation (～7.3 log reduction) within 60 min, whereas treatment with 100% ethanol resulted in only a ～4.7 log reduction, and 100% isopropanol resulted in a 5.2-log reduction. Peracetic acid (peroxyacetic acid) at the highest concentration used (0.45%) resulted in only a ～4.-log reduction of phage within 60 min. The results of this study provide additional information on effective treatments for the eradication of potential phage infections in dairy plants.     

Monitoring ultraviolet (UV) radiation inactivation of Cronobacter sakazakii in dry infant formula using Fourier transform infrared spectroscopy

Cronobacter sakazakii is an opportunistic pathogen associated with dry infant formula presenting a high risk to low birth weight neonates. The inactivation of C. sakazakii in dry infant formula by ultraviolet (UV) radiation alone and combined with hot water treatment at temperatures of 55, 60, and 65 °C were applied in this study. UV radiation with doses in a range from 12.1 ± 0.30 kJ/m2 to 72.8 ± 1.83 kJ/m2 at room temperature demonstrated significant inactivation of C. sakazakii in dry infant formula (P < 0.05). UV radiation combining 60 °C hot water treatment increased inactivation of C. sakazakii cells significantly (P < 0.05) in reconstituted infant formula. Significant effects of UV radiation on C. sakazakii inactivation kinetics (D value) were not observed in infant formula reconstituted in 55 and 65 °C water (P > 0.05). The inactivation mechanism was investigated using vibrational spectroscopy. Infrared spectroscopy detected significant stretching mode changes of macromolecules on the basis of spectral features, such as DNA, proteins, and lipids. Minor changes on cell membrane composition of C. sakazakii under UV radiation could be accurately and correctly monitored by infrared spectroscopy coupled with 2nd derivative transformation and principal component analysis.     

超声波在食品灭菌中的研究进展

综述超声波及其相关技术对李斯特单胞菌，沙门氏菌，大肠杆菌，金黄色葡萄球菌，枯草芽孢杆菌等微生物灭菌效果的研究进展。虽然超声波自身用于食品灭菌不是很有效，但是热超声波、压力超声波以及压热超声波是很有前景的，其灭菌效果非常显著。     

LED在UV印刷方面的应用及发展动向

<正>一、LED的发光原理LED是Light Emitting Diode的简称,是一种有电流流动就发光的半导体,也被称为发光二极管(见图1)。LED的发光原理如图2所示,在LED芯片上极性方向加电压,芯片中的电子和正电荷就移动,即电流流动。在移动中,电子     

Use of linear, Weibull, and log-logistic functions to model pressure inactivation of seven foodborne pathogens in milk

Survival curves of six foodborne pathogens suspended in ultra high-temperature (UHT) whole milk and exposed to high hydrostatic pressure at 21.5 degrees C were obtained. Vibrio parahaemolyticus was treated at 300 MPa and other pathogens, Listeria monocytogenes, Escherichia coli O157:H7, Salmonella enterica serovar Enteritidis, Salmonella enterica serovar Typhimurium, and Staphylococcus aureus were treated at 600 MPa. All the survival curves showed a rapid initial drop in bacterial counts followed by tailing caused by a diminishing inactivation rate. A linear model and two nonlinear models were fitted to these data and the performances of these models were compared using mean square error (MSE) values. The log-logistic and Weibull models consistently produced better fits to the inactivation data than the linear model. The mean MSE value of the linear model was 6.1, while the mean MSE values were 0.7 for the Weibull model and 0.3 for the log-logistic model. There was no correlation between pressure resistance and the taxonomic group the bacteria belong to. The order, most to least pressure-sensitive, of the single strains tested was: V. parahaemolyticus (gram negative)相似文献   

紫外吸收剂及其在皮革化学品上的应用

紫外线吸收剂是一类可防止太阳光或其它人造紫外光引起聚合物降解的物质。针对现有无机、有机紫外吸收剂的应用发展现状和趋势,介绍了有机紫外吸收剂中的二苯甲酮类、苯并三唑类、受组胺类以及无机紫外吸收剂中纳米氧化锌、纳米二氧化钛和稀土类纳米氧化物的紫外吸收原理和应用。最后针对紫外吸收剂在皮革用染料、皮革用加脂剂、皮革用涂饰剂等皮革化学品中的应用现状进行介绍,并对以后的发展趋势进行展望。