Comparison of chlorine and peroxyacetic-based disinfectant to inactivate Feline calicivirus, Murine norovirus and Hepatitis A virus on lettuce

In recent years, raw fruits and vegetables have frequently been involved in foodborne transmission to humans of enteric viruses, particularly noroviruses and hepatitis A virus (HAV). Although viral contamination can occur during all steps of food processing, primary production is a critical stage on which prevention measures must be focused to minimize the risk of infection to consumers. Postharvest sanitation may be a valid technological solution for decreasing the bacterial load on fresh raw material, but there is a lack of data concerning the effectiveness of this process on enteric viruses. In this study, we compared the survival of two human norovirus surrogates, the feline calicivirus (FCV), and the murine norovirus (MNV-1), and of HAV on lettuce after water washing with bubbles and with or without ultrasound, and washing with bubbles in the presence of active chlorine (15 ppm) or peroxyacetic acid-based disinfectant (100 ppm). Cell culture and quantitative RT-PCR assays were used to detect and quantify the viruses on the surface of the lettuce after the sanitizing treatments. Levels of viral inactivation on the lettuce leaves were not significantly different between washing with bubbles and washing with bubbles plus ultrasound and were not dependant on the quantification method. A simple washing without disinfectant resulted in a decrease of approximately 0.7 log units in the quantity of virus detected for HAV and FCV and of 1.0 log unit for MNV-1.In the experimental set-up including a washing step (with or without ultrasound) followed by washing for 2 min in the presence of disinfectants, 15 ppm of active chlorine was found more effective for inactivating FCV (2.9 log units) than HAV and MNV-1 (1.9 log units and 1.4 log units, respectively) whereas 100 ppm of peroxyacetic-based biocide was found effective for inactivating FCV (3.2 log units) and MNV-1 (2.3 log units), but not HAV (0.7 log units). Quantitative RT-PCR results indicated that the presence of viral RNA did not correlate with the presence of infectious viruses on disinfected lettuce, except for MNV-1 processed with chlorine (15 ppm). In comparison with water washing, a substantial additional decrease of genomic FCV titer (1.1 log units) but no significant reduction of the genomic titers of HAV and MNV-1 were found on lettuce treated with chlorine (15 ppm). No significant effect of the disinfection step of lettuce with peroxyacetic-based biocide (100 ppm peracetic acid) was found by qRT-PCR on all genomic viral titers tested. This study illustrates the necessity of determining the effectiveness of technological processes against enteric viruses, using a relevant reference such as HAV, in order to reduce the risk of hepatitis and gastroenteritis by exposure to vegetables.     

Efficacy of a novel sanitizer composed of lactic acid and peroxyacetic acid against single strains of nonpathogenic Escherichia coli K-12, Listeria innocua, and Lactobacillus plantarum in aqueous solution and on surfaces of romaine lettuce and spinach

A novel sanitizer composed of lactic acid and peroxyacetic acid (LA-PAA) was developed as an alternative to chlorinated water (CW) for fresh produce processing. Single strains of Lactobacillus plantarum, nonpathogenic Escherichia coli K-12, and Listeria innocua were used to demonstrate the microbial efficacy of LA-PAA. LA-PAA achieved a >7.8-log reduction of L. innocua and L. plantarum suspended in water at 4°C for 20 s, and LA, PAA, and CW achieved reductions of 0.4, 4.8, and 2.7 log, respectively. LA-PAA, when compared with LA, PAA, and CW, enhanced the reduction of L. innocua attached to romaine leaves by >2.2 log, and improved the removal of E. coli attached to spinach leaves by >2.4 log. The exponential improvement in the microbial efficacy of LA-PAA showed synergism between LA and PAA. LA-PAA microbial efficacy was inversely proportional to pH value and directly correlated with residence time and concentration. Despite an improvement in microbial reduction through the addition of surfactant to LA-PAA, the usage of surfactant in washing fresh produce was impeded by excessive foaming during actual processing. Effects of organic matter on the performance of LA-PAA were minimal. External sensory evaluations showed that LA-PAA had no negative effects on the quality of lettuce and tender leaves. Temperature-abuse studies demonstrated that LA-PAA reduced decay by ～50% when compared with CW. Overall, these results support the premise that LA-PAA has significant potential to be an alternative to CW for fresh produce processing.     

Efficacy of a levulinic Acid plus sodium dodecyl sulfate-based sanitizer on inactivation of human norovirus surrogates

Human noroviruses are the most common etiologic agent of foodborne illness in the United States. The inability to culture human noroviruses in the laboratory necessitates the use of surrogate viruses such as murine norovirus (MNV-1) and feline calicivirus (FCV) for inactivation studies. In this study, a novel sanitizer of organic acid (levulinic acid) plus the anionic detergent sodium dodecyl sulfate (SDS) was evaluated. Viruses were treated with levulinic acid (0.5 to 5%), SDS (0.05 to 2%), or combinations of levulinic acid plus SDS (1:10 solution of virus to sanitizer). MNV-1 inoculated onto stainless steel also was treated with a 5% levulinic acid plus 2% SDS liquid or foaming solution. Log reductions of viruses were determined with a plaque assay. Neither levulinic acid nor SDS alone were capable of inactivating MNV-1 or FCV, resulting in a ≤0.51-log reduction of the infectious virus titer. However, the combination of 0.5% levulinic acid plus 0.5% SDS inactivated both surrogates by 3 to 4.21 log PFU/ml after 1 min of exposure. Similarly, MNV-1 inoculated onto stainless steel was reduced by >1.50 log PFU/ml after 1 min and by >3.3 log PFU/ml after 5 min of exposure to a liquid or foaming solution of 5% levulinic acid plus 2% SDS. The presence of organic matter (up to 10%) in the virus inoculum did not significantly affect sanitizer efficacy. The fact that both of the active sanitizer ingredients are generally recognized as safe to use as food additives by the U.S. Food and Drug Administration further extends its potential in mitigating foodborne disease.     

Decontamination of green onions and baby spinach by vaporized ethyl pyruvate

Foodborne illnesses associated with fresh produce continue to be a major concern as consumer demand for healthier and nonthermally processed food increases. The objective of this study was to evaluate vaporized ethyl pyruvate (EP; CAS 617-35-6) as a safe alternative antimicrobial agent for the decontamination of Escherichia coli O157:H7 on green onions and spinach. Baby spinach leaves and green onions were inoculated with a five-strain cocktail of E. coli O157:H7 (pGFP) by the dipping method. Samples were treated with concentrations of 0, 42, 105, and 420 mg/liter vaporized EP in a 2.6-liter enclosed container. The efficacy of EP vapors for reducing E. coli O157:H7((GFP)) populations on green onions and baby spinach at 4 and 10°C was monitored for 7 and 5 days, respectively. The lowest EP concentration (42 mg/liter) resulted in a 1.7-log reduction of E. coli O157:H7((GFP)) on green onions after 7 days at 4°C and a 1.9-log reduction after 5 days at 10°C (P < 0.05). In baby spinach, the same concentration resulted in 0.9-log and 1.4-log reductions (P < 0.05) of E. coli O157:H7((GFP)) after 7 days at 4°C and 5 days at 10°C, respectively. On green onions, the highest concentration of EP (420 mg/liter) reduced the population of E. coli O157:H7((GFP)) by >4.7 log CFU/g after 7 days at 4°C and 5 days at 10°C. The same concentration was also effective for reducing E. coli O157:H7((GFP)) populations in baby spinach by 4.3 log CFU/g after 7 days at 4°C and by >6.5 log CFU/g after 3 days at 10°C. Although the successful EP treatments minimally affected the sensory attributes of green onions, the treatments resulted in significant changes in the sensory attributes of baby spinach samples stored at 4 and 10°C. These results indicate that EP is an effective antimicrobial that could be used to enhance the safety of fresh produce depending on the sensory characteristics of the product.     

Heterogeneous photocatalytic disinfection of wash waters from the fresh-cut vegetable industry

The effectiveness of photocatalytic disinfection for control of natural and potentially pathogenic microflora in wash waters used for fresh-cut vegetables was evaluated. Wash waters for lettuce, escarole, chicory, carrot, onion, and spinach from a fresh-cut vegetable processing plant were treated with a titanium dioxide (TiO2) photocatalytic system. The vegetable wash waters were impelled out with a pump at a flow rate of 1,000 liters/h and conducted through a stainless steel circuit to the filtration system to reach the TiO2 photocatalyst fiber, which was illuminated with a 40-W UV-C lamp. The microbial and physicochemical qualities of the wash water were analyzed. Heterogeneous photocatalysis was an effective disinfection method, reducing counts of bacteria, molds, and yeasts. Most of the treated wash waters had total bacteria reductions of 4.1 +/- 1.3 to 4.8 +/- 0.4 log CFU/ml after 10 min of treatment when compared with untreated water. Higher decontamination efficacy was observed in carrot wash water (6.2 +/- 0.1-log reductions), where turbidity and organic matter were lower than those in the wash waters for other vegetables. The tested heterogeneous photocatalytic system also was effective for reducing water turbidity, although chemical oxygen demand was unaffected after the treatments. The efficacy of the photocatalytic system for reducing microbial load depended on the physicochemical characteristics of the wash water, which depended on the vegetable being washed. The conclusions derived from this study illustrate that implementation of a heterogeneous photocatalytic system in the fresh-cut vegetable washing processes could allow the reuse of wash water.     

Comparison of reduction in foodborne viral surrogates by high pressure homogenization

With the increasing global spread of human noroviral infections and the emergence of highly virulent noroviral strains, novel inactivation methods are needed to control foodborne outbreaks. High pressure homogenization (HPH) is a novel method that can be applied for foodborne virus reduction in fluids being continuously processed. Our objective in the present study was to compare the titer reduction by HPH between feline calicivirus strain F9 (FCV-F9) and murine norovirus 1 (MNV-1) as surrogates for human noroviruses, and MS2 (single-stranded F-RNA coliphage) and somatic coliphage φX174 (single-stranded DNA) as indicators of fecal contamination. Duplicate experiments with each virus in phosphate-buffered saline were carried out with homogenization pressures of 0, 100, 200, 250, and 300 MPa, with exposure temperatures of 24, 46, 63, 70, and 75°C, respectively, for <2 s. FCV-F9 was found highly susceptible to HPH treatment pressures of 300 MPa, with a reduction of >4.95 log PFU/ml. Lower pressures of 250, 200, and 100 MPa resulted in reductions of 1.61, 0.60, and 0.18 log PFU/ml of FCV-F9, respectively, while MNV-1 was not reduced at these lower pressures. Coliphage φX174 showed no significant reduction at 300 MPa or lower homogenization pressures in comparison with MS2, which did show 3.3-log PFU/ml reduction at 300 MPa. Future studies using juices for industrial application of HPH to determine microbial inactivation with simultaneous retention of sensory and nutritional value of foods are needed.     

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.     

Relative efficacy of sodium hypochlorite wash versus irradiation to inactivate Escherichia coli O157:H7 internalized in leaves of Romaine lettuce and baby spinach

Pathogenic bacteria that become internalized in leaf tissues are protected from the antimicrobial effects of surface treatments. Ionizing radiation is known to penetrate food tissues, but the efficacy of the process against internalized bacteria is unknown. Leaves of Romaine lettuce and baby spinach were cut into pieces, submerged in a cocktail mixture of three isolates of Escherichia coli O157:H7, and subjected to a vacuum perfusion process to force the bacterial cells into the intercellular spaces in the leaves. Scanning electron microscopy was used to evaluate the efficacy of the perfusion process. The inoculated leaves were then treated with a 3-min water wash, a 3-min wash with a sodium hypochlorite sanitizing solution (300 or 600 ppm), or various doses of ionizing radiation (0.25 to 1.5 kGy). Leaves were stomached to recover the internalized pathogen cells, which were enumerated. The vacuum perfusion effectively forced bacteria into the leaf vasculature and apoplast, as confirmed by scanning electron microscopy. For spinach leaf pieces, neither the water nor the sodium hypochlorite washes resulted in significant reductions of E. coli O157:H7 cells relative to the untreated control. For Romaine lettuce leaf pieces, 300 and 600 ppm sodium hypochlorite each resulted in less than 1-log reduction; water wash was ineffective. Ionizing radiation, in contrast, significantly reduced the pathogen population, with 4-log (Romaine lettuce) or 3-log (spinach) reductions at the highest dose tested. In Romaine leaves, the reduction was dose dependent across the range of doses tested, with a D10-value (the amount of irradiation necessary to reduce the population by 1 log unit) of 0.39 kGy. In spinach leaves, the pathogen had a biphasic response, with a D10-value of 0.27 kGy in the range of 0 to 0.75 kGy but only slight additional reductions from 0.75 to 1.5 kGy. In this study, ionizing radiation but not chemical sanitizers effectively reduced viable E. coli O157:H7 cells internalized in leafy green vegetables, but the response of the pathogen to irradiation was more complex in spinach leaves than in Romaine lettuce leaves.     

Fate of Escherichia coli O157:H7 in manure compost-amended soil and on carrots and onions grown in an environmentally controlled growth chamber

Studies were done to determine the fate of Escherichia coli O157:H7 in manure compost-amended soil and on carrots and green onions grown in an environmentally controlled growth chamber. Commercial dairy cattle manure compost was inoculated with a five-strain mixture of green fluorescent protein-labeled E. coli O157:H7 at 10(7) CFU g(-1) and mixed with unsterilized Tifton sandy loam soil at a ratio of 1:5. Baby carrot or green onion seedlings were planted into the manure compost-amended soil in pots, and soil samples surrounding the plant, edible carrot roots and onion bulb samples, and soil immediately beneath the roots were assayed for E. coli O157:H7 in triplicate at weekly intervals for the first 4 weeks, and every 2 weeks for the remainder of the plant growth cycle (up to 3 months). E. coli O157:H7 cell numbers decreased within 64 days by 3 log CFU/g in soil and soil beneath the roots of green onions and by more than 2 log CFU/g on onions. E. coli O157:H7 survived better during the production of carrots, with a 2.3-log CFU/g reduction in soil and a 1.7-log CFU/g reduction on carrots within 84 days. These results indicate that the type of plant grown is an important factor influencing the survival of E. coli O157:H7 both on the vegetable and in the soil in which the vegetable is grown.     

Survival of human norovirus surrogates in milk, orange, and pomegranate juice, and juice blends at refrigeration (4 °C)

Fresh fruits, juices, and beverages have been implicated in human noroviral and hepatitis A virus outbreaks. The purpose of this study was to determine the survival of human norovirus surrogates (murine norovirus, MNV-1; feline calicivirus, FCV-F9; and bacteriophage MS2) in juices (orange and pomegranate juices), juice blends (pomegranate and orange juice) and milk over 0, 1, 2, 7, 14, and 21 days at refrigeration (4 °C). Juices, juice blends, and milk were inoculated with each virus over 21 days, serially diluted in cell culture media, and plaque assayed. MNV-1 showed no reduction in titer after 21 days in orange juice and milk, but moderate reduction (1.4 log) in pomegranate juice from a titer of 5 log(10) PFU/ml. However, MNV-1 was completely reduced after 7 days in the orange and pomegranate juice blend. FCV-F9 from a titer of 6 log(10) PFU/ml was completely reduced after 14 days in orange as well as pomegranate juice and by ～ 3 logs after 21 days in milk at 4 °C. Interestingly, FCV-F9 was completely reduced after 1 day in the orange and pomegranate juice blend at 4 °C. MS2 was reduced by ～ 1.28 log after 21 days in orange juice from a titer of 6 log(10) PFU/ml, and <1 log after 21 days in milk or pomegranate juice, with juice blends showing minimal reduction (<1 log) after 21 days at 4 °C. These results show the survival pattern of noroviruses that aid in the transmission of foodborne viral outbreaks. The data obtained can be used in quantitative viral risk assessment studies and to develop improved measures to prevent virus survival towards controlling outbreaks.     

Electron-beam inactivation of a norovirus surrogate in fresh produce and model systems

Norovirus remains the leading cause of foodborne illness, but there is no effective intervention to eliminate viral contaminants in fresh produce. Murine norovirus 1 (MNV-1) was inoculated in either 100 ml of liquid or 100 g of food. The inactivation of MNV-1 by electron-beam (e-beam), or high-energy electrons, at varying doses was measured in model systems (phosphate-buffered saline [PBS], Dulbecco's modified Eagle's medium [DMEM]) or from fresh foods (shredded cabbage, diced strawberries). E-beam was applied at a current of 1.5 mA, with doses of 0, 2, 4, 6, 8, 10, and 12 kGy. The surviving viral titer was determined by plaque assays in RAW 264.7 cells. In PBS and DMEM, e-beam at 0 and 2 kGy provided less than a 1-log reduction of virus. At doses of 4, 6, 8, 10, and 12 kGy, viral inactivation in PBS ranged from 2.37 to 6.40 log, while in DMEM inactivation ranged from 1.40 to 3.59 log. Irradiation of inoculated cabbage showed up to a 1-log reduction at 4 kGy, and less than a 3-log reduction at 12 kGy. On strawberries, less than a 1-log reduction occurred at doses up to 6 kGy, with a maximum reduction of 2.21 log at 12 kGy. These results suggest that a food matrix might provide increased survival for viruses. In foods, noroviruses are difficult to inactivate because of the protective effect of the food matrix, their small sizes, and their highly stable viral capsid.     

Ozone inactivation of norovirus surrogates on fresh produce

Preharvest contamination of produce by foodborne viruses can occur through a variety of agents, including animal feces/manures, soil, irrigation water, animals, and human handling. Problems of contamination are magnified by potential countrywide distribution. Postharvest processing of produce can involve spraying, washing, or immersion into water with disinfectants; however, disinfectants, including chlorine, have varying effects on viruses and harmful by-products pose a concern. The use of ozone as a disinfectant in produce washes has shown great promise for bacterial pathogens, but limited research exists on its efficacy on viruses. This study compares ozone inactivation of human norovirus surrogates (feline calicivirus [FCV] and murine norovirus [MNV]) on produce (green onions and lettuce) and in sterile water. Green onions and lettuce inoculated with FCV or MNV were treated with ozone (6.25 ppm) for 0.5- to 10-min time intervals. Infectivity was determined by 50% tissue culture infectious dose (TCID(50)) and plaque assay for FCV and MNV, respectively. After 5 min of ozone treatment, >6 log TCID(50)/ml of FCV was inactivated in water and ～2-log TCID(50)/ml on lettuce and green onions. MNV inoculated onto green onions and lettuce showed a >2-log reduction after 1 min of ozone treatment. The food matrix played the largest role in protection against ozone inactivation. These results indicate that ozone is an alternative method to reduce viral contamination on the surface of fresh produce.     

超声联合过氧乙酸清洗对生姜品质的影响

目的 考查浸泡、振荡、超声单独或协同方式及其联合过氧乙酸(peroxide acetic acid, PAA)清洗对生姜表面泥沙、微生物去除效果及对贮藏品质的影响。方法 比较水清洗、PAA溶液清洗、超声清洗及其组合的12种清洗方式对生姜表面泥沙、霉菌和酵母菌、电解质泄漏率、呼吸强度、失重率、总酚含量、总黄酮含量、抗氧化性等比较分析得出最佳的清洗方式。结果 与水振荡清洗相比, PAA显著提高了泥沙清洁率(5.31%降低至4.50%) , 且与超声清洗协同可显著增加清洁率(4.50%降低至1.85%), 清洗前浸泡显著提高泥沙清洁率(约0.7%)。PAA清洗降低生姜表面微生物约0.8 log CFU/g, 而联合超声后可降低2.2 log CFU/g。超声促进了电解质泄漏, 超声处理时间越长, 电解质泄漏率越高。储藏期间清洗的生姜失重率显著增加, 超声清洗30 min后生姜储藏期间呼吸强度显著升高。与水振荡清洗相比, PAA溶液对生姜总多酚、总黄酮含量没有显著影响, 但超声波清洗30 min总酚含量显著下降, 抗氧化活性变化趋势与之一致。结论 使用PAA溶液, 先浸泡, 然后超声, 最后振荡(各10 min)的联合清洗方式是生姜最佳的清洗方式。     

An innovative water-assisted UV-C disinfection system to improve the safety of strawberries frozen under cryogenic conditions

Strawberries inoculated with Salmonella enterica, Listeria monocytogenes (10⁸ CFU/mL, 50 μL) and murine norovirus (MNV-1; 10⁶ TCID₅₀/mL, 50 μL), were washed for 2 min in a water-assisted UV-C light tank (WUVC) combined or not with 40 mg/L of peracetic acid (WUVC+PA), and 200 mg/L of free chlorine solution (NaClO) with the UV-C lamps switched off. Moreover, a ‘conventional’ dry UV-C treatment (DUVC) was also tested. After 2-min exposure, washing sanitization with chemical agents gave the highest reduction for both bacteria (ca. ≥ 3.3 log CFU/g) and MNV-1 (≥1.8 log TCID₅₀/mL). DUVC treatment proved to be the least effective technology (≤0.6 log CFU/g for bacteria and 1.5 log TCID₅₀/mL for MNV-1). Regarding wash water, no presence of L. monocytogenes and S. enterica were reported with WUVC+PA and NaClO sanitization. After disinfection, samples were frozen at −70 ± 2 °C in a cryogenic freezing cabinet with liquid nitrogen (N₂). For both pathogens, frozen storage after washing substantially enhanced their inactivation in the first 3 days (1.1–4.9 log UFC/g) compared to the reductions obtained the following sampling points (0.0–0.8 log UFC/g). After 90 days, L. monocytogenes and S. enterica were not detected on the samples treated with water-assisted methodologies (WUVC, WUVC+PA and NaClO treatments), whilst MNV-1 was little affected. Further studies are needed to improve norovirus inactivation on frozen strawberries.Industrial relevanceThe present work provides relevant information to the frozen food industry regarding a suitable decontamination alternative to chlorine sanitation. Low-dose immersion-assisted UV-C allows inactivation and inhibition of pathogenic microbiota while generates non-toxic byproducts and allows reusing the process water, contributing to the so-called “smart green growth” attended to provide a more innovative and sustainable future for the food industry.     

Long-term storage of onion and the factors that affect its quality: A critical review

Storage of onions is a multifaceted issue, which involves many preharvest and postharvest factors. One of the major factors that affect onion storage is the selection of the proper cultivar, since there are significant differences in storability between the cultivars and not all of them are suitable for storage. Proper preharvest and postharvest conditions are essential for storability of onion bulbs, whereas they also affect marketability (weight losses, texture and color depth of bulbs) and quality (chemical composition, nutritional value, antioxidant activity). Irrigation and fertilization are essential preharvest factors that substantially affect storability, whereas curing methods and storage conditions (temperature, relative humidity, controlled atmospheres) and processing treatments are postharvest factors. This review article examines the effect of long-term storage on the main quality features of onions, such as the incidence of sprouting and root growth, water losses, and changes in chemical composition (mineral composition, sugar content, nutritional value) and antioxidant activity (phenolic and flavonoid contents, DPPH [2,2-diphenyl-1-picrylhydrazyl] scavenging activity).     

Effect of hand wash agents on controlling the transmission of pathogenic bacteria from hands to food

The goals of this study were to evaluate the effectiveness of two hand wash regimens in reducing transient bacteria on the skin following a single hand wash and the subsequent transfer of the bacteria to a ready-to-eat food item, freshly cut cantaloupe melon. The number of bacteria recovered from hands and the quantity transferred to the melon were significantly less following the use of an antibacterial soap compared with plain soap. The antimicrobial soap achieved > 3-log reductions versus Escherichia coli and 3.31- and 2.83-log reductions versus Shigella flexneri. The plain soap failed to achieve a 2-log reduction against either organism. The bacteria recovered from the melon handled by hands treated with antimicrobial hand soap averaged 2 log. Melon handled following hand washing with plain soap had > 3 log bacteria in the experiments. Based on previously published feeding studies, an infection rate in the range of approximately 15 to 25% would be expected after ingesting melon containing 2 log CFU compared with ingesting greater than the 3 log transferred from hands washed with plain soap, which would result in a higher infection attack rate of 50 to 80%. The data thus demonstrate there is a greater potential to reduce the transmission and acquisition of disease through the use of an antimicrobial hand wash than through the use of plain soap.     

Effects of Lactic Acid and Commercial Chilling Processes on Survival of Salmonella, Yersinia enterocolitica, and Campylobacter coli in Pork Variety Meats

Current industry chilling practices with and without the application of 2% L-lactic acid were compared for their effectiveness at reducing levels of Salmonella, Yersinia enterocolitica, and Campylobacter coli on pork variety meats. Pork variety meats (livers, intestines, hearts, and stomachs) were inoculated individually with one of the three pathogens and subjected to five different treatment combinations that included one or more of the following: water wash (25°C), lactic acid spray (2%, 40 to 50°C), chilling (4°C), and freezing (-15°C). Samples were analyzed before treatment, after each treatment step, and after 2, 4, and 6 months of frozen storage. Results showed that when a lactic acid spray was used in combination with water spray, immediate reductions were approximately 0.5 log CFU per sample of Salmonella, 0.8 log CFU per sample of Y. enterocolitica, and 1.1 log CFU per sample of C. coli. Chilling, both alone and in combination with spray treatments, had little effect on pathogens, while freezing resulted in additional 0.5-log CFU per sample reductions in levels of Salmonella and Y. enterocolitica, and an additional 1.0-log CFU per sample reduction in levels of C. coli. While reductions of at least 1 log CFU per sample were observed on variety meats treated with only a water wash and subsequently frozen, samples treated with lactic acid had greater additional reductions than those treated with only a water spray throughout frozen storage. The results of this study suggest that the use of lactic acid as a decontamination intervention, when used in combination with good manufacturing practices during processing, causes significant reductions in levels of Salmonella, Y. enterocolitica, and C. coli on pork variety meats.     

Detection of onion postharvest diseases by analyses of headspace volatiles using a gas sensor array and GC-MS

Onion postharvest diseases cause significant losses in storage. Volatile sensing by the gas sensor array technology could be used as a promising alternative method to detect onion diseases. Onions were inoculated with Botrytis allii and Burkholderia cepacia, causal pathogen for Botrytis neck rot and sour skin, respectively. In the first phase of this study, 30 onions with equal number of B. allii inoculated and control healthy onions were measured by the gas sensor array from 8 to 11 days after inoculation (dai) and the principal component analysis (PCA) score plot demonstrated that the gas sensor array responded differently to Botrytis neck rot infected onions from those of healthy onions. In the second phase, 30 onions with 10 for each of the three treatments (Botrytis neck rot, sour skin, control) were measured by the gas sensor array on 5, 6, and 7 dai. The PCA score plot illustrated that three treatments formed three distinct clusters, while a hierarchical cluster analysis dendrogram indicated that the response of the gas sensor array to Botrytis neck rot and sour skin were similar. The correct classification rate of the linear discriminant model for three treatments was over 97.8%. Results from GC-MS showed that total 24 major volatiles were identified from the headspace of three treatments. Sixteen compounds were uniquely present in B. allii and B. cepacia inoculated onion bulbs. Total amount of volatile compounds detected in pathogen inoculated bulbs was one to two orders of magnitude higher than that of control healthy bulbs. This study demonstrated the feasibility of using a gas sensor array to detect two onion postharvest diseases in storage.     

Disinfection potential of ozone, ultraviolet-C and their combination in wash water for the fresh-cut vegetable industry

The purpose of this research was to investigate the disinfection efficacy of ozone (O₃) and UV-C illumination (UV), and their combination (O₃–UV) for reducing microbial flora of fresh-cut onion, escarole, carrot, and spinach wash waters collected from the industry. Furthermore, the influence of water physicochemical parameters on the decontamination efficacy and the effect of these technologies on physicochemical quality of wash water were analyzed. O₃, UV, and O₃–UV were effective disinfection treatments on vegetable wash water, with a maximum microbial reduction of 6.6 log CFU mL⁻¹ after 60 min treatment with O₃–UV. However, maximum total microbial reductions achieved by UV and O₃ treatments after 60 min were 4.0 and 5.9 log CFU mL⁻¹, lower than by O₃–UV treatment. Furthermore, turbidity of wash water was reduced significantly by O₃ and O₃–UV treatments, while UV treatment did not affect the physicochemical quality of the water. Conclusions derived from this study illustrate that O₃ and O₃–UV are alternatives to other sanitizers used in the fresh-cut washing processes. The use of these technologies would allow less frequent changing of spent water and the use of much lower sanitizer doses. Nevertheless, in specific applications such as carrot wash water, where levels of undesirable microbial and chemical constituents are lower than other vegetable wash water, UV treatment could be an appropriate treatment considering cost-effectiveness criteria.