Inactivation of Escherichia coli O157:H7 on Inoculated Alfalfa Seeds with Pulsed Ultraviolet Light and Response Surface Modeling

: Escherichia coli O157:H7‐inoculated alfalfa seeds with seed layer thicknesses of 1.02 to 6.25 mm were subjected to pulsed UV light for up to 90 s at a 8‐cm distance from the UV strobe. Population reductions higher than 4 log₁₀ colony‐forming units (CFU)/g were achieved. For effect of distance from the UV strobe, seeds with 6.25‐mm layer thickness were treated 3 to 13 cm from the strobe. Reductions at shorter distances, such as 60 s at 5 cm (1.93 log₁₀ CFU/g) and 60 to 90 s at 8 cm (4.89 log₁₀ CFU/g), were significantly higher (P≤ 0.05). Data from the treatments were used to develop empirical models as a function of distance or layer thickness and treatment time for predicting the population of E. coli O157:H7 during pulsed UV‐light treatment. This study demonstrates that pulsed UV light holds promise for eliminating pathogens from alfalfa seeds, and the models developed can be useful predictive tools.     

Efficacy of Slightly Acidic Electrolyzed Water and UV‐Ozonated Water Combination for Inactivating Escherichia Coli O157:H7 on Romaine and Iceberg Lettuce during Spray Washing Process

Spray washing is a common sanitizing method for the fresh produce industry. The purpose of this research was to investigate the antimicrobial effect of spraying slightly acidic electrolyzed water (SAEW) and a combination of ozonated water with ultraviolet (UV) in reducing Escherichia coli O157:H7 on romaine and iceberg lettuces. Both romaine and iceberg lettuces were spot inoculated with 100 μL of a 3 strain mixture of E. coli O157:H7 to achieve an inoculum of 6 log CFU/g on lettuce. A strong antimicrobial effect was observed for the UV‐ozonated water combination, which reduced the population of E. coli by 5 log CFU/g of E. coli O157:H7 on both lettuces. SAEW achieved about 5 log CFU/g reductions in the bacterial counts on romaine lettuce. However, less than 2.5 log CFU/g in the population of E. coli O157:H7 was reduced on iceberg lettuce. The difference may be due to bacteria aggregation near and within stomata for iceberg lettuce but not for romaine lettuce. The UV light treatment may stimulate the opening of the stomata for the UV‐ozonated water treatment and hence achieve better bacterial inactivation than the SAEW treatment for iceberg lettuce. Our results demonstrated that the combined treatment of SAEW and UV‐ozonated water in the spray washing process could more effectively reduce E. coli O157:H7 on lettuce, which in turn may help reduce incidences of E. coli O157:H7 outbreaks.     

超声-微酸性电解水联合处理对腐败希瓦氏菌的作用机制

研究超声（ultrasound,US）-微酸性电解水（slightly acidic electrolyzed water,SAEW）联合处理对腐败希瓦氏菌的作用机制。分别对腐败希瓦氏菌菌悬液进行US、SAEW、超声-微酸性电解水（US+SAEW）联合处理10 min,以无菌生理盐水处理腐败菌为对照（CK）组。通过减菌效果、细菌生长曲线、电导率、碘化丙啶摄入量、碱性磷酸酶（alkaline phosphatase,AKP）与乳酸脱氢酶（lactate dehydrogenase,LDH）活力、紫外吸收物质泄漏量等指标测定菌体细胞膜及内环境变化,并结合扫描电子显微镜对处理前后的菌体微观结构进行观察。结果表明,US+SAEW联合处理可使腐败希瓦氏菌菌落总数降低2.48(lg(CFU/mL));与CK组和单一处理组相比,US+SAEW联合处理使菌体细胞膜的完整性受到明显破坏,导致其细胞质泄漏,电导率、AKP与LDH活力显著升高（P<0.05）。同时,US+SAEW联合处理后,菌体塌陷明显、外膜出现断裂、细胞壁受损,内容物大量外泄。因此,US+SAEW联合处理能在US使腐败希瓦氏菌的细胞...     

Efficacy of Sulfuric Acid Scarification and Disinfectant Treatments in Eliminating Escherichia coli O157: H7 from Alfalfa Seeds Prior to Sprouting

ABSTRACT: E. coli O157:H7 reduction on inoculated alfalfa seeds was investigated using acid scarification treatments with or without subsequent application of sanitizers. Scarification with 0.1 to 2N H₂SO₄ for 2.5 to 45 min did not affect (p ≤ 0.05) seed viability. E. coli O157:H7 was reduced by 2.1 to 5.0 logs after treating with 0.1 to 2N H₂SO₄ for 5 to 20 min. Combined scarification (0.5N H₂SO₄) and H₂O₂ or CH₃COOH treatments enhanced microbial destruction by less than 1 log compared to sanitizer alone. Chlorine, Na₂CO₃, or Na₃PO₄ treatments preceded by scarification did not significantly increase microbial destruction compared to sanitizer alone. Appreciable reductions in seed germination were only observed with chlorine treatments.     

Efficacy of Neutral pH Electrolyzed Water in Reducing Escherichia coli O157:H7 and Salmonella Typhimurium DT 104 on Fresh Produce Items using an Automated Washer at Simulated Food Service Conditions

The objective of this study was to determine the efficacy of neutral pH electrolyzed (NEO) water (155 mg/L free chlorine, pH 7.5) in reducing Escherichia coli O157:H7 and Salmonella Typhimurium DT 104 on romaine lettuce, iceberg lettuce, and tomatoes washed in an automated produce washer for different times and washing speeds. Tomatoes and lettuce leaves were spot inoculated with 100 μL of a 5 strain cocktail mixture of either pathogen and washed with 10 or 8 L of NEO water, respectively. Washing lettuce for 30 min at 65 rpm led to the greatest reductions, with 4.2 and 5.9 log CFU/g reductions achieved for E. coli O157:H7 and S. Typhimurium respectively on romaine, whereas iceberg lettuce reductions were 3.2 and 4.6 log CFU/g for E. coli O157:H7 and S. Typhimurium respectively. Washing tomatoes for 10 min at 65 rpm achieved reductions greater than 8 and 6 log CFU/tomato on S. Typhimurium and E. coli O157:H7 respectively. All pathogens were completely inactivated in NEO water wash solutions. No detrimental effects on the visual quality of the produce studied were observed under all treatment conditions. Results show the adoption of this washing procedure in food service operations could be useful in ensuring produce safety.     

Storage Stability of Slightly Acidic Electrolyzed Water and Circulating Electrolyzed Water and Their Property Changes after Application

Slightly acidic electrolyzed water (SAEW) has been recognized as an effective bactericidal agent with free chlorine, but its limitations include its instability and its great dependence on equipment. Newly developed circulating electrolyzed water (CEW) with a higher available chlorine concentration (ACC) could successfully overcome these limitations. In this study, SAEW (ACC of 20 mg/L), CEW₁ (ACC of 200 mg/L), and CEW₂ (ACC of 20 mg/L) were evaluated for changes in properties (pH, oxidization reduction potential [ORP], and ACC) during storage in open or closed glass bottles under light or dark conditions at room temperature (approximately 20 °C) and after washing pork and lettuce. Additionally, the washed pork and lettuce were evaluated for total viable counts, pH and general appearance. The results showed that CEW₁ with a higher ACC has better stability than SAEW with a lower ACC for the storage and washing experiments, and CEW still remained stable after dilution with distilled water. The property indices of EW were greatly affected for the pork‐washing experiments compared with the lettuce‐washing experiments, probably due to the existence of alkaline and organic materials on the surface of pork. Furthermore, EWs were more effective for inactivating microbes in lettuce than in pork, while there was no significant difference in tissue pH and the general appearance of pork and lettuce. These findings indicated that CEW with a higher ACC shows potential for reducing foodborne pathogens on pork and lettuce without effects on their physicochemical characteristics, and it can be applied in a diluted form.     

Survival and Growth of Vibrio cholerae O1, Salmonella typhi, and Escherichia coli O157:H7 in Alfalfa Sprouts

The survival and growth of Vibrio cholerae O1, Salmonella typhi , and Escherichia coli O157:H7 during germination and sprouting of disinfected alfalfa seeds and alfalfa sprouts was determined. All pathogens showed ability to grow during germination and sprouting, reaching counts of approximately 6.0 log₁₀ CFU/g after 24 h. No growth was observed for any pathogen when the sprouts were inoculated after 24 h of seed germination. At this time, the background microflora was abundant. Numbers of pathogens inoculated on alfalfa sprouts decreased less than 1 log10 CFU/g over 15 d of refrigeration. Alfalfa sprouts can be an important factor contributing to the endemicity for typhoid fever and cholera in México.     

Seed Viability and Functional Properties of Broccoli Sprouts during Germination and Postharvest Storage as Affected by Irradiation of Seeds

ABSTRACT:  The viability of broccoli seeds and functional properties, such as ascorbic acid, carotenoid, chlorophyll, and total phenol contents, of broccoli sprouts grown from irradiated seeds were evaluated. The seeds were irradiated using electron beam and gamma ray at doses up to 8 kGy. High germination percentages (>90%) were observed in seeds irradiated at ≤4 kGy, but the yield ratio and sprout length decreased with increased irradiation dose. Irradiation at ≥6 kGy resulted in curling of the sprout roots. Germinated seeds contained higher amounts of nutrients than raw seeds but the nutritional quality of sprouts decreased during postharvest storage. Radiation treatment hampered the growth of irradiated seeds resulting in underdeveloped sprouts with decreased ascorbic acid, carotenoid, and chlorophyll contents. In addition, the decrease in functional content of sprouts was more substantial in samples grown from high-dose (5 kGy) irradiated seeds than that of the low-dose (1 kGy) treated ones. Seed irradiation did not negatively affect the total phenol content of sprouts. In general, electron beam and gamma irradiation of broccoli seeds showed similar effects on the viability and functional properties of sprouts.     

Effect of Surface Roughness on Retention and Removal of Escherichia coli O157:H7 on Surfaces of Selected Fruits

ABSTRACT:  This study was undertaken to evaluate the effect of surface roughness on the attachment and removal of Escherichia coli O157:H7 on selected fruit and metal surfaces. A new method to determine surface roughness was developed using confocal laser scanning microscopy (CLSM). A series of 2-D layered images were taken by CLSM optical slicing of the surfaces of Golden Delicious apples, navel oranges, avocadoes, and cantaloupes. The average roughness ( R_a ) of the fruit surfaces was assessed by reconstructing a series of 2-D images into 3-D images. A cocktail of 5 E. coli O157:H7 strains were spot inoculated onto fruit skin surfaces with different R_a . The fruits were then treated with acidic electrolyzed water (AEW), peroxyacetic acid (POAA), and sterilized deionized water. Aluminum stubs with different R_a values as a model system were also spot inoculated with E. coli O157:H7 and subjected to a sonication treatment. Test results indicated that there was a positive linear correlation between R_a and adhesion rate of E. coli O157:H7, and a negative correlation between R_a and the efficacy of inactivation by AEW and POAA, respectively, on fruit surfaces. A linear increase of residual bacteria population with increased surface roughness of aluminum stubs was also observed. The relationship between surface roughness and surface hydrophobicity was negative linear for the aluminum stubs, but was quadratic for the 4 fruits. The environmental scanning electron microscopy images showed that bacteria tended to attach to or be entrapped in the grooves or cavities of fruits, which provided protection to the cells against washing treatments.     

酸性电解水对罗非鱼片的杀菌工艺研究

文章旨在优化酸性电解水对罗非鱼片的杀菌工艺,开发一种新型的罗非鱼片减菌预处理方式.考察酸性电解水杀菌方式、氧化还原电位(ORP)、杀菌时间及料液比对罗非鱼片杀菌率的影响,采用单因素试验和正交试验优化杀菌工艺,并以过氧化氢作对照,评价酸性电解水的杀菌效果及其对罗非鱼片感官和质构的影响.结果 表明:酸性电解水对罗非鱼片的最...     

Efficacy of High Hydrostatic Pressure Treatment in Reducing Escherichia coli O157 and Listeria monocytogenes in Alfalfa Seeds

ABSTRACT: The application of high hydrostatic pressure (HHP) technology as a seed decontamination technique was evaluated. Alfalfa seeds inoculated with Escherichia coli O157 and Listeria monocytogenes were air-dried and subjected to independent HHP treatments of 275 to 575 MPa for 2 min or at 475 MPa for 2 to 8 min (40°C). There were 1.4-log and 2.0-log reductions in E. coli O157 populations at 575 MPa (2 min) and 475 MPa (8 min), respectively. However, these treatments caused only 0.8-log and 1.1-log reductions in L. monocytogenes counts. Treated seeds took longer to germinate, achieving germination rate of up to 34%, whereas 95% of the control germinated. Results suggest that L. monocytogenes is more resistant to the bactericidal effects of HHP than E. coli O157. Although HHP treatments achieved a greater reduction in E. coli O157, it was at the expense of seed germination. Overall, our results indicate that although HHP treatments reduced the populations of E. coli O157 and L. monocytogenes in alfalfa seeds, they did not completely eliminate these microorganisms.     

Survival of Listeria monocytogenes, Yersinia enterocolitica and Escherichia coli O157:H7 and Quality Changes After Irradiation of Beef Steaks and Ground Beef

Beef steaks and ground beef were inoculated with Listeria monocytogenes, Yersinia enterocolitica, or Escherichia coli O157:H7. Samples were packaged in air or under vacuum and irradiated at low (0.60 to 0.80 kGy) or medium (1.5 to 2.0 kGy) doses, with each dose delivered at either a low (2.8 M/min conveyor speed) or high (6.9 M/min) dose rate. Medium-dose irradiation accompanied by 7°C storage resulted in no Y. enterocolitica or E. coli O157:H7 survivors being detected. There was no effect on survival of the pathogens by dose rate or storage atmosphere. No difference (P>0.05) was observed in meat pH or color, but TBA values increased after 7 days storage.     

西兰花籽中萝卜硫苷的提取、分离及结构鉴定

摘 要：本文研究了一种从西兰花籽中提取分离萝卜硫苷(4-甲基亚磺酰丁基硫代葡萄糖苷)的方法。用甲醇溶液从西兰花籽中提取硫苷,经弱阴离子交换树脂纯化得到萝卜硫苷粗品,通过半液相制备色谱进一步分离纯化,制得萝卜硫苷纯品。并利用液-质联用、核磁共振、红外、紫外等方法对其进行结构确定,结果符合萝卜硫苷的分子结构。此方法适用于萝卜硫苷的简单有效提取。     

Determination and Health Implication of the Erucic Acid Content of Broccoli Florets, Sprouts, and Seeds

The erucic acid content of broccoli florets, sprouts, and seeds was found to be about 0.8, 320, and 12100 mg/100 g, respectively. Using the erucic acid limit established for canola oil in the U.S.A. and Canada as a guideline, the estimated dietary intake of erucic acid from florets and sprouts was considered of little consequence, whereas in seeds a relatively small amount (about 35 g/wk) equaled our calculated exposure limit for erucic acid. Additionally, the most complete fatty acid distribution yet published for the various forms of broccoli are presented.     

石榴皮渣果胶电解水提取工艺及其结构特性

以石榴皮渣为研究对象,采用超声波辅助电解水法提取石榴皮渣果胶,优化石榴皮渣果胶的提取工艺,并分析其物质组成与结构特性。在单因素试验基础上,借助Box-Behnken试验设计优化,获得石榴皮渣果胶的最佳提取工艺条件:超声功率密度1 W/mL、pH 1.7、提取温度60℃、提取时间33 min和料液比1∶18(g/mL),石榴皮渣果胶提取得率达到14.95%。相比于超纯水提取工艺,其提取得率提高了2.2%,且电解水提取法得到的果胶具有更低的分子质量(7.294×10⁶ g/mol)和更高的D-半乳糖醛酸质量分数(70.29%),并通过化学滴定法与傅里叶变换红外光谱手段共同说明了电解水提取法得到的果胶具有更高的酯化度。由此可知,超声辅助电解水提取法是一种高效、环保的提取方法,该结果为提高石榴果实产品附加值和实现副产物高效综合利用提供了技术支撑。     

Inactivation of E. coli O157:H7 on blueberries by electrolyzed water, ultraviolet light, and ozone

Increased interest in blueberries due to their nutritional and health benefits has led to an increase in consumption. However, blueberries are consumed mostly raw or minimally processed and are susceptible to microbial contamination like other type of fresh produce. This study was, therefore, undertaken to evaluate the efficacy of electrostatic spray of electrolyzed oxidizing (EO) water, UV light, ozone, and a combination of ozone and UV light in killing Escherichia coli O157:H7 on blueberries. A 5-strain mixture of E. coli O157:H7 were inoculated on the calyx and skin of blueberries and then subjected to the treatments. Electrostatic EO water spray reduced initial populations of E. coli O157:H7 by only 0.13 to 0.24 log CFU/g and 0.88 to 1.10 log CFU/g on calyx and skin of blueberries, respectively. Ozone treatment with 4000 mg/L reduced E. coli O157:H7 by only 0.66 and 0.72 log CFU/g on calyx and skin of blueberries, respectively. UV light at 20 mW/cm2 for 10 min was the most promising single technology and achieved 2.14 and greater than 4.05 log reductions of E. coli O157:H7 on the calyx and skin of blueberries, respectively. The combination treatment of 1 min ozone and followed by a 2 min UV achieved more than 1 and 2 log additional reductions on blueberry calyx than UV or ozone alone, respectively. PRACTICAL APPLICATION: Outbreaks of foodborne illnesses have been associated with consumption of fresh produce. Many methods for removing pathogens as well as minimizing their effect on quality of treated produce have been investigated. UV technology and its combination with ozone used in this study to inactive E. coli O157:H7 on blueberries was found effective. Results from this study may help producers and processors in developing hurdle technologies for the delivery of safer blueberries to consumers.     

酸性电解水对果蔬杀菌及保鲜效果的研究

本研究采用酸性电解水对新鲜菠菜、桃子及樱桃进行处理,考察了酸性电解水对上述果蔬在不同贮藏条件下保鲜效果的影响.结果表明,pH 3.04、有效氯浓度(ACC)30.2 mg/kg的强酸性电解水和pH 5.68、ACC 26.6 mg/kg的微酸性电解水浸泡处理5min均能使菠菜表面的微生物数下降2.0lg cfu/g以上...     

酸性电解水对南美白对虾中多酚氧化酶活性的影响

酸性电解水（acidic electrolyzed water,AEW）作为一种新型的杀菌保鲜技术已经被应用于海产品的保 鲜方面,实践表明AEW对南美白对虾的黑变有抑制效果。为了探究其作用机理,将南美白对虾中多酚氧化酶 （polyphenoloxidase,PPO）进行提取纯化,并研究AEW对PPO的抑制效果及抑制类型。十二烷基硫酸钠-聚丙烯酰 胺凝胶电泳结果显示,PPO的提纯效果较为理想;动力学研究发现,AEW对PPO活力具有显著抑制效果,且其作用 大小与AEW添加量呈明显的剂量-效应关系。AEW对PPO抑制类型为混合型抑制,抑制常数Ki为0.64 mmol/L。实验 结果为进一步探明AEW抑制南美白对虾黑变的作用机理提供了理论基础。     

Escherichia coli O157:H7 Biofilm Formation on Romaine Lettuce and Spinach Leaf Surfaces Reduces Efficacy of Irradiation and Sodium Hypochlorite Washes

Abstract: Escherichia coli O157:H7 contamination of leafy green vegetables is an ongoing concern for consumers. Biofilm-associated pathogens are relatively resistant to chemical treatments, but little is known about their response to irradiation. Leaves of Romaine lettuce and baby spinach were dip inoculated with E. coli O157:H7 and stored at 4 °C for various times (0, 24, 48, 72 h) to allow biofilms to form. After each time, leaves were treated with either a 3-min wash with a sodium hypochlorite solution (0, 300, or 600 ppm) or increasing doses of irradiation (0, 0.25, 0.5, 0.75, or 1 kGy). Viable bacteria were recovered and enumerated. Chlorine washes were generally only moderately effective, and resulted in maximal reductions of 1.3 log CFU/g for baby spinach and 1.8 log CFU/g for Romaine. Increasing time in storage prior to chemical treatment had no effect on spinach, and had an inconsistent effect on 600 ppm applied to Romaine. Allowing time for formation of biofilm-like aggregations reduced the efficacy of irradiation. D₁₀ values (the dose required for a 1 log reduction) significantly increased with increasing storage time, up to 48 h postinoculation. From 0 h of storage, D₁₀ increased from 0.19 kGy to a maximum of 0.40 to 0.43 kGy for Romaine and 0.52 to 0.54 kGy for spinach. SEM showed developing biofilms on both types of leaves during storage. Bacterial colonization of the stomata was extensive on spinach, but not on Romaine. These results indicate that the protection of bacteria on the leaf surface by biofilm formation and stomatal colonization can reduce the antimicrobial efficacy of irradiation on leafy green vegetables. Practical Application: Before incorporating irradiation into the overall GMP/GHP chain, a packer or processor of leafy green vegetables must determine at what stage of processing and shipping the irradiation should take place. As a penetrating process, irradiation is best applied as a postpackaging intervention. Time in refrigerated storage between packaging and processing may alter the antimicrobial efficacy of irradiation. Irradiation on a commercial scale should include efforts to minimize the time delay between final packaging and irradiation of leafy vegetables.     

应用PCR-DGGE监测酸性电解水对虾的杀菌效果

目的：考察酸性电解水对虾的杀菌效果。样品虾处理方法为：室温(20℃)条件下酸性电解水处理不同时间(处理1min或5min);不同温度(20℃或50℃)酸性电解水处理5min;室温(20℃)条件下不同处理液(酸性电解水或2%乙酸)处理5min。利用平板培养结合PCR-DGGE技术监测酸性电解水对虾的杀菌效果。结果：50℃酸性电解水处理,虾中菌数减少1.44 lg(CFU/g),其他处理减少小于1.0 lg(CFU/g);不同处理时间对杀菌效果影响不显著;2%乙酸或50℃酸性电解水的杀菌效果显著高于室温酸性电解水(P＜0.05);PCR-DGGE指纹图谱分析结果显示：50℃酸性电解水处理后,虾中细菌种类不变,其他处理比对照(无处理)有不同程度的减少;处理1min的DGGE指纹图谱和对照极相似;50℃酸性电解水处理和对照中等不相似;其他处理和对照中等相似。结论：50℃酸性电解水对虾具有较好的杀菌效果,PCR-DGGE技术能用于监测酸性电解水对虾的杀菌效果。