Interactions between Microbial Food Safety and Environmental Sustainability in the Fresh Produce Supply Chain.

Improving the environmental sustainability of the food supply chain will help to achieve the United Nations Sustainable Development Goals (SDGs). This environmental sustainability is related to different SDGs, but mainly to SDG 2 (Zero Hunger), SDG 12 (Responsible Production and Consumption), SDG 13 (Climate Action), and SDG 15 (Life on Land). The strategies and measures used to improve this aspect of the food supply chain must remain in balance with other sustainability aspects (economic and social). In this framework, the interactions and possible conflicts between food supply chain safety and sustainability need to be assessed. Although priority must be given to safety aspects, food safety policies should be calibrated in order to avoid unnecessary deleterious effects on the environment. In the present review, a number of potential tensions and/or disagreements between the microbial safety and environmental sustainability of the fresh produce supply chain are identified and discussed. The addressed issues are spread throughout the food supply chain, from primary production to the end-of-life of the products, and also include the handling and processing industry, retailers, and consumers. Interactions of fresh produce microbial safety with topics such as food waste, supply chain structure, climate change, and use of resources have been covered. Finally, approaches and strategies that will prove useful to solve or mitigate the potential contradictions between fresh produce safety and sustainability are described and discussed. Upon analyzing the interplay between microbial safety and the environmental sustainability of the fresh produce supply chain, it becomes clear that decisions that are taken to ensure fresh produce safety must consider the possible effects on environmental, economic, and social sustainability aspects. To manage these interactions, a global approach considering the interconnections between human activities, animals, and the environment will be required.

Reusable Plastic Crates (RPCs) for Fresh Produce (Case Study on Cauliflowers): Sustainable Packaging but Potential Salmonella Survival and Risk of Cross-Contamination.

The handling of fresh fruits and vegetables in reusable plastic crates (RPCs) has the potential to increase the sustainability of packaging in the fresh produce supply chain. However, the utilization of multiple-use containers can have consequences related to the microbial safety of this type of food. The present study assessed the potential cross-contamination of fresh cauliflowers with Salmonella enterica via different contact materials (polypropylene from RPCs, corrugated cardboard, and medium-density fiberboard (MDF) from wooden boxes). Additionally, the survival of the pathogenic microorganism was studied in cauliflowers and the contact materials during storage. The life cycle assessment (LCA) approach was used to evaluate the environmental impact of produce handling containers made from the different food-contact materials tested. The results show a higher risk of cross-contamination via polypropylene compared with cardboard and MDF. Another outcome of the study is the potential of Salmonella for surviving both in cross-contaminated produce and in contact materials under supply chain conditions. Regarding environmental sustainability, RPCs have a lower environmental impact than single-use containers (cardboard and wooden boxes). To exploit the potential environmental benefits of RPCs while ensuring food safety, it is necessary to guarantee the hygiene of this type of container.

Critical points affecting the microbiological safety of bell peppers washed with peroxyacetic acid in a commercial packinghouse.

The washing stage from a bell pepper commercial packinghouse was assessed to study some of the critical control points related to bacterial cross-contamination. The washing line comprised two overhead spray bars applications: a pre-wash step without peroxyacetic acid (PAA), and a wash step with PAA. The physicochemical characteristics of the wash water and the bacterial quality and safety of the wash water and bell peppers (including aerobic mesophilic bacteria (AMB), Salmonella spp., and Shiga-toxigenic E. coli (STEC)) were studied. Additionally, the performance of commercial test methods (reflectometry, amperometric probe, chronoamperometric sensor) for measuring the residual concentration of PAA was examined. The bacterial load of the pre-wash water (8.7 ± 1.3 log cfu/100 mL AMB) was very high and thus peppers after the pre-wash showed a significantly higher bacterial load (4.9 ± 0.9 log cfu/g AMB) than the unwashed (3.8 ± 0.7 log cfu/g AMB) or the washed peppers (3.3 ± 0.8 log cfu/g AMB) (p < 0.05). However, no pathogenic bacteria were detected in bell pepper samples (n = 40), and only one water sample was confirmed positive for STEC (n = 64, 1.6% prevalence). The chronoamperometric sensor (PAASense) and the online amperometric probe showed similar results, while the reflectometry (Quantofix) significantly sub estimated (p < 0.05) PAA concentration. The results obtained highlight the need for interventions to improve hygiene in the washing line to ensure the microbiological quality and safety of bell peppers. The maintenance of optimal PAA concentrations in all the washing steps is critical for reducing the chance of water-mediated cross-contamination.

Suitability of centrifuge water for detecting the presence of Escherichia coli versus finished fresh-cut lettuce testing.

Fresh produce causes most foodborne outbreaks in the USA, and it is also considered a hazardous food product in other areas of the world such as Europe. The outbreaks attributed to fresh produce increase the focus of producers on hygiene to minimize exposure to food hazards. The fresh produce industry has the urgent need to detect if there are production lots contaminated with pathogenic microorganisms before distribution. Although the industry is mostly using end-product testing for the detection of target microorganisms, previous studies have evaluated the suitability of different sampling points within the production line of a fresh-cut processing plant. In the present study, the centrifuge effluent water was assessed as an alternative sampling point to end-product testing. E. coli was selected as an index microorganism of the presence of pathogens. The presence of E. coli was assessed in centrifuge effluent water, and fresh-cut lettuce from a commercial fresh-cut produce processing line (n = 95). The rate of false positives and negatives, as well as the specificity, sensitivity, and efficiency of the alternative method were calculated. The mean population of E. coli in positive water samples was 0.86 log cfu/100 mL, while the mean population of E. coli in positive fresh-cut lettuce samples was 0.23 log cfu/g. The proportion of positive samples in centrifuge effluent water and lettuce was similar (≈20%), and most of the results in both matrices were coincident (81.1%). However, the alternative method was not reliable due to its low sensitivity, as only 47.6% of the lettuce samples positive for E. coli could be matched with positive water samples.

Agricultural reuse of municipal wastewater through an integral water reclamation management.

The DESERT-prototype, a state-of-the-art compact combination of water treatment technologies based on filtration and solar-based renewable energy, was employed to reclaim water for agricultural irrigation. Water reclaimed through the DESERT-prototype (PW) from a secondary effluent of a wastewater treatment plant, as well as conventional irrigation water (CW) and the secondary effluent (SW) itself, were employed to cultivate baby romaine lettuces in a greenhouse in Murcia (Spain), by means of drip and sprinkler irrigation methods, thus establishing six treatments. Assessments of physicochemical and microbiological quality of irrigation water, as well as agronomic and microbiological quality of crops from all treatments, showed that results associated to PW complied in all cases with relevant standards and guidelines. In contrast, results linked to SW and CW presented certain non-compliance cases of water and crop microbiological quality. These assessments lead to conclude that the DESERT-prototype is an appropriate technology for safe water reclamation oriented to agricultural production, that can be complemented by a proper irrigation method in reaching safety targets.

Demonstration tests of irrigation water disinfection with chlorine dioxide in open field cultivation of baby spinach.

BACKGROUND: Treatments for the disinfection of irrigation water have to be evaluated by demonstration tests carried out under commercial settings taking into account not only their antimicrobial activity but also the potential phytotoxic effects on the crop. The consequences of the treatment of irrigation water with chlorine dioxide (ClO2 ) used for sprinkler irrigation of baby spinach in two commercial agricultural fields was assessed. RESULTS: Residual ClO2 levels at the sprinklers in the treated field were always below 1 mg L-1 . ClO2 treatment provoked limited but statistically significant reductions in culturable Escherichia coli counts (0.2-0.3 log reductions), but not in the viable E. coli counts in water, suggesting the presence of viable but non-culturable cells (VBNC). Although disinfected irrigation water did not have an impact on the microbial loads of Enterobacteriaceae nor on the quality characteristics of baby spinach, it caused the accumulation of chlorates (up to 0.99 mg kg-1 in plants) and the reduction of the photosynthetic efficiency of baby spinach. CONCLUSION: Low concentrations of ClO2 are effective in reducing the culturable E. coli present in irrigation water but it might induce the VBNC state. Presence of disinfection by-products and their accumulation in the crop must be considered to adjust doses in order to avoid crop damage and chemical safety risks. © 2017 Society of Chemical Industry.

Disinfection by-products in baby lettuce irrigated with electrolysed water.

BACKGROUND: Irrigation water disinfection reduces the microbial load but it might lead to the formation and accumulation of disinfection by-products (DBPs) in the crop. If DBPs are present in the irrigation water, they can accumulate in the crop, particularly after the regrowth, and be affected by the postharvest handling such as washing and storage. To evaluate the potential accumulation of DBPs, baby lettuce was grown using irrigation water treated with electrolysed water (EW) in a commercial greenhouse over three consecutive harvests and regrowths. The impact of postharvest practices such as washing and storage on DBP content was also assessed. RESULTS: Use of EW caused the accumulation of chlorates in irrigation water (0.02-0.14 mg L-1 ), and in the fresh produce (0.05-0.10 mg kg-1 ). On the other hand, the disinfection treatment had minor impact regarding the presence of trihalomethanes (THMs) in water (0.3-8.7 µg L-1 max), and in baby lettuce (0.3-2.9 µg kg-1 max). CONCLUSIONS: Disinfection of irrigation water with EW caused the accumulation of chlorates in the crop reaching levels higher than the current maximum residual limit established in the EU legislation for leafy greens. © 2017 Society of Chemical Industry.

Impact of relative humidity, inoculum carrier and size, and native microbiota on Salmonella ser. Typhimurium survival in baby lettuce.

The effects of relative humidity (RH), fluctuating climate conditions, inoculum size and carrier on the survival of Salmonella enterica serovar Typhimurium on baby lettuce in environmental test chambers were studied. Buffered peptone water (BPW), distilled water (DW), and irrigation water (IW) were compared as inoculum carriers. Additionally, survival of Salmonella in suspensions prepared using filtered and unfiltered IW was assessed. Salmonella Typhimurium survived better on baby lettuce plants at high RH independently of the inoculum size. When lettuce plants were grown under fluctuating environmental conditions, Salmonella survival was similar under both RH conditions. Regarding the inoculum carrier, the inoculated microorganism survived better on lettuce plants when BPW was used as carrier both at high and low RH. Survival rate of Salmonella in IW was affected by the presence of native microbiota. Native microbiota present in IW did not affect survival of Salmonella or the levels of mesophilic bacteria on the baby lettuce leaves. The information obtained in the present study contributes to the knowledge on the effect of environmental conditions on pathogenic bacteria survival on growing edible plants. These results are useful when selecting the methodology to carry out experimental studies on the survival of microbial pathogens under different pre-harvest conditions.

Evaluation of viability PCR performance for assessing norovirus infectivity in fresh-cut vegetables and irrigation water.

Norovirus (NoV) detection in food and water is mainly carried out by quantitative RT-PCR (RT-qPCR). The inability to differentiate between infectious and inactivated viruses and the resulting overestimation of viral targets is considered a major disadvantage of RT-qPCR. Initially, conventional photoactivatable dyes (i.e. propidium monoazide, PMA and ethidium monoazide, EMA) and newly developed ones (i.e. PMAxx and PEMAX) were evaluated for the discrimination between infectious and thermally inactivated NoV genogroup I (GI) and II (GII) suspensions. Results showed that PMAxx was the best photoactivatable dye to assess NoV infectivity. This procedure was further optimized in artificially inoculated lettuce. Pretreatment with 50µM PMAxx and 0.5% Triton X-100 (Triton) for 10min reduced the signal of thermally inactivated NoV by ca. 1.8 logs for both genogroups in lettuce concentrates. Additionally, this pretreatment reduced the signal of thermally inactivated NoV GI between 1.4 and 1.9 logs in spinach and romaine and lamb's lettuces and by >2 logs for NoV GII in romaine and lamb's lettuce samples. Moreover this pretreatment was satisfactorily applied to naturally-contaminated water samples with NoV GI and GII. Based on the obtained results this pretreatment has the potential to be integrated in routine diagnoses to improve the interpretation of positive NoV results obtained by RT-qPCR.

Safety assessment of greenhouse hydroponic tomatoes irrigated with reclaimed and surface water.

The impact of reclaimed and surface water on the microbiological safety of hydroponic tomatoes was assessed. Greenhouse tomatoes were irrigated with reclaimed and surface water and grown on two hydroponic substrates (coconut fiber and rock wool). Water samples (n=208) were taken from irrigation water, with and without the addition of fertilizers and drainage water, and hydroponic tomatoes (n=72). Samples were analyzed for indicator microorganisms, generic Escherichia coli and Listeria spp., and pathogenic bacteria such as Salmonella spp. and Shiga-toxigenic E. coli (STEC), using multiplex real-time PCR (RT-PCR) after enrichment. The correlation between climatological parameters such as temperature and the levels of microorganisms in water samples was also determined. In irrigation water, generic E. coli counts were higher in reclaimed than in surface water whereas Listeria spp. numbers increased after adding the fertilizers in both water sources. In drainage water, no clear differences in E. coli and Listeria numbers were observed between reclaimed and surface water. No positive samples for STEC were found in irrigation water. Presumptive positives for Salmonella spp. were found in 7.7% of the water samples and 62.5% of these samples were reclaimed water. Salmonella-positive samples by RT-PCR could not be confirmed by conventional methods. Higher concentrations of E. coli were associated with Salmonella-presumptive positive samples. Climatological parameters, such as temperature, were not correlated with the E. coli and Listeria spp. counts. Tomato samples were negative for bacterial pathogens, while generic E. coli and Listeria spp. counts were below the detection limit. The prevalence of presumptive Salmonella spp. found in irrigation water (reclaimed and surface water) was high, which might present a risk of contamination. The absence of pathogens on greenhouse hydroponic tomatoes indicates that good agricultural practices (GAP) were in place, avoiding the microbial contamination of the fruit.

Modeling growth of Escherichia coli O157:H7 in fresh-cut lettuce treated with neutral electrolyzed water and under modified atmosphere packaging.

The purpose of this study was to evaluate and model the growth of Escherichia coli O157:H7 in fresh-cut lettuce submitted to a neutral electrolyzed water (NEW) treatment, packaged in passive modified atmosphere and subsequently stored at different temperatures (4, 8, 13, 16°C) for a maximum of 27 days. Results indicated that E. coli O157:H7 was able to grow at 8, 13, and 16°C, and declined at 4°C. However at 8°C, the lag time lasted 19 days, above the typical shelf-life time for this type of products. A secondary model predicting growth rate as a function of temperature was developed based on a square-root function. A comparison with literature data indicated that the growth predicted by the model for E. coli O157:H7 was again lower than those observed with other disinfection treatments or packaging conditions (chlorinated water, untreated product, NEW, etc.). The specific models here developed might be applied to predict growth in products treated with NEW and to improve existing quantitative risk assessments.

Modelling growth of Escherichia coli O157:H7 in fresh-cut lettuce submitted to commercial process conditions: chlorine washing and modified atmosphere packaging.

Fresh-cut iceberg lettuce inoculated with Escherichia coli O157:H7 was submitted to chlorine washing (150 mg/mL) and modified atmosphere packaging on laboratory scale. Populations of E. coli O157:H7 were assessed in fresh-cut lettuce stored at 4, 8, 13 and 16 °C using 6-8 replicates in each analysis point in order to capture experimental variability. The pathogen was able to grow at temperatures ≥8 °C, although at low temperatures, growth data presented a high variability between replicates. Indeed, at 8 °C after 15 days, some replicates did not show growth while other replicates did present an increase. A growth primary model was fitted to the raw growth data to estimate lag time and maximum growth rate. The prediction and confidence bands for the fitted growth models were estimated based on Monte-Carlo method. The estimated maximum growth rates (log cfu/day) corresponded to 0.14 (95% CI: 0.06-0.31), 0.55 (95% CI: 0.17-1.20) and 1.43 (95% CI: 0.82-2.15) for 8, 13 and 16 °C, respectively. A square-root secondary model was satisfactorily derived from the estimated growth rates (R(2) > 0.80; Bf = 0.97; Af = 1.46). Predictive models and data obtained in this study are intended to improve quantitative risk assessment studies for E. coli O157:H7 in leafy green products.

Electrochemical disinfection: an efficient treatment to inactivate Escherichia coli O157:H7 in process wash water containing organic matter.

The efficacy of an electrochemical treatment in water disinfection, using boron-doped diamond electrodes, was studied and its suitability for the fresh-cut produce industry analyzed. Tap water (TW), and tap water supplemented with NaCl (NaClW) containing different levels of organic matter (Chemical Oxygen Demand (COD) around 60, 300, 550 ± 50 and 750 ± 50 mg/L) obtained from lettuce, were inoculated with a cocktail of Escherichia coli O157:H7 at 105 cfu/mL. Changes in levels of E. coli O157:H7, free, combined and total chlorine, pH, oxidation-reduction potential, COD and temperature were monitored during the treatments. In NaClW, free chlorine was produced more rapidly than in TW and, as a consequence, reductions of 5 log units of E. coli O157:H7 were achieved faster (0.17, 4, 15 and 24 min for water with 60, 300, 500 and 750 mg/L of COD, respectively) than in TW alone (0.9, 25, 60 min and 90 min for water with 60, 300, 600 and 800 mg/L of COD, respectively). Nonetheless, the equipment showed potential for water disinfection and organic matter reduction even without adding NaCl. Additionally, different mathematical models were assessed to account for microbial inactivation curves obtained from the electrochemical treatments.

Cross-contamination of fresh-cut lettuce after a short-term exposure during pre-washing cannot be controlled after subsequent washing with chlorine dioxide or sodium hypochlorite.

Chlorine dioxide (ClO(2)) has been postulated as an alternative to sodium hypochlorite (NaClO) for fresh-cut produce sanitization to avoid risks associated with chlorination by-products. Experiments were performed to determine the prevention of cross-contamination of fresh-cut lettuce by Escherichia coli using chlorine dioxide (3 mg/L) or sodium hypochlorite (100 mg/L) as sanitation agents. The efficacy of these sanitation solutions was evaluated simulating as much as possible the conditions of a fresh-cut processing line. Thus, to evaluate the potential risk of cross-contamination during pre-washing, inoculated fresh-cut lettuce was pre-washed and after that non-inoculated lettuce was then pre-washed in the same water. After this pre-washing, non-inoculated lettuce was cross-contaminated, changing from 0 to 3.4 log units of E. coli cells. During washing with sanitizers, none of the tested sanitation agents significantly reduced E. coli counts in both inoculated and cross-contaminated lettuce. These results suggest that when cross-contamination occurs, even if the event is recent, subsequent sanitation steps are inefficient for inactivating E. coli cells on the vegetable tissue. However, chlorine dioxide and sodium hypochlorite solutions were able to inactivate most E. coli cells that passed from inoculated product to wash water. Therefore, they might be able to avoid cross-contamination between clean and contaminated product during the washing step. Scanning electron microscopy micrographs indicated that bacterial cells were mainly located in clusters or tissue stomata where they might be protected, which explains the low efficacy of sodium hypochlorite and chlorine dioxide solutions observed in this study.

Characterization of Escherichia coli from raw poultry in Belgium and impact on the detection of Campylobacter jejuni using Bolton broth.

A comparative study examining Bolton broth and Preston broth for enrichment and reliable detection of Campylobacter jejuni (both healthy and freeze stressed cells) was performed. Tested as pure cultures, Bolton broth enabled faster resuscitation and growth of C. jejuni compared to Preston broth. When C. jejuni was co-incubated with extended-spectrum-beta-lactamase (ESBL) producing Escherichia coli isolated from Belgian poultry meat preparations, the latter dominated in the Bolton enrichment broth and crowded the mCCDA plates. This resulted in the inability to recover C. jejuni by ISO 10272-1:2006 standard method. Preston broth did not support the growth of the ESBL E. coli isolates, but showed longer detection time of C. jejuni compared to Bolton broth. The use of the same antibiotic (sodium cefoperazone) in Bolton broth and in mCCDA plates may explain the problems encountered for detection of C. jejuni, as high numbers of ESBL E. coli present after enrichment in Bolton broth, also caused overgrowth and masked the few C. jejuni colonies present on the mCCDA plates. The use of Campylobacter spp. specific real-time PCR circumvented these problems and enabled rapid detection of the pathogen after 24h enrichment in both Bolton and Preston broth, for both healthy and freeze stressed cells.

Prevention of Escherichia coli cross-contamination by different commercial sanitizers during washing of fresh-cut lettuce.

The efficacy of fresh-cut produce sanitizers has mainly been evaluated by measuring microbial reductions on produce. However, its suitability to ensure that pathogens are rapidly killed avoiding cross-contamination of subsequent product also needs to be considered. The efficacy of chlorine, Tsunami, Citrox and Purac on non pathogenic Escherichia coli reductions in processing water and on fresh-cut lettuce were studied. Selection of minimum effective doses was carried out in processing water, which contained a chemical oxygen demand (COD) within the range of 700-1000 mg/l and a total mesophilic load of about 7 log CFU/ml. The processing water was inoculated with two inoculum levels (3 and 5 log CFU/ml). It was observed that 40 mg/l of chlorine and 500 mg/l of Tsunami were effective in reducing the inoculum levels in the processing water to the detection limit (5 and 4 log units). However, Citrox and Purac were not effective in reducing E. coli population even at the highest manufacturer's recommended doses. Evaluation of cross-contamination in fresh-cut lettuce was carried out by measuring E. coli transfer from inoculated (~5 log CFU/g) to uninoculated lettuce after washing the contaminated product in the water containing different sanitizing agents. Chlorine and Tsunami were able to inactivate E. coli in wash water, avoiding cross-contamination between contaminated and non-contaminated product. However, Citrox and Purac at the recommended doses did not prevent transfer of E. coli cells between inoculated and uninoculated fresh-cut lettuce and therefore indicating cross-contamination. The results obtained show that chlorine and Tsunami are recommended as water disinfection agents preventing E. coli cross-contamination of produce during processing.

Fresh-cut product sanitation and wash water disinfection: problems and solutions.

It is well known that fresh-cut processors usually rely on wash water sanitizers to reduce microbial counts in order to maintain quality and extend shelf-life of the end product. Water is a useful tool for reducing potential contamination but it can also transfer pathogenic microorganisms. Washing with sanitizers is important in fresh-cut produce hygiene, particularly removing soil and debris, but especially in water disinfection to avoid cross-contamination between clean and contaminated product. Most of the sanitizing solutions induce higher microbial reduction after washing when compared to water washing, but after storage, epiphytic microorganisms grow rapidly, reaching similar levels. In fact, despite the general idea that sanitizers are used to reduce the microbial population on the produce, their main effect is maintaining the microbial quality of the water. The use of potable water instead of water containing chemical disinfection agents for washing fresh-cut vegetables is being advocated in some European countries. However, the problems of using an inadequate sanitizer or even none are considered in this manuscript. The need for a standardized approach to evaluate and compare the efficiency of sanitizing agents is also presented. Most new alternative techniques accentuate the problems with chlorine suggesting that the industry should move away from this traditional disinfection agent. However, the use of chlorine based sanitizers are presented as belonging to the most effective and efficient sanitizers when adequate doses are used. In this review improvements in water disinfection and sanitation strategies, including a shower pre-washing step and a final rinse of the produce, are suggested.

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 (O(3)) and UV-C illumination (UV), and their combination (O(3)-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. O(3), UV, and O(3)-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 O(3)-UV. However, maximum total microbial reductions achieved by UV and O(3) treatments after 60 min were 4.0 and 5.9 log CFU mL(-1), lower than by O(3)-UV treatment. Furthermore, turbidity of wash water was reduced significantly by O(3) and O(3)-UV treatments, while UV treatment did not affect the physicochemical quality of the water. Conclusions derived from this study illustrate that O(3) and O(3)-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.

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.

Impact of wash water quality on sensory and microbial quality, including Escherichia coli cross-contamination, of fresh-cut escarole.

The influence of wash water quality on the microbial load and sensory quality of fresh-cut escarole was evaluated. Additionally, the degree of Escherichia coli cross-contamination between inoculated and uninoculated products after washing was also studied. Three types of wash water, i.e., potable water, diluted recirculated water, and recirculated water, containing different microbial counts and organic loads, were used. Results showed that microbial load (P > or = 0.02) and sensory quality (P > 0.625) of the product were not influenced by the water quality after washing and storage. Cross-contamination between inoculated and uninoculated products was observed after washing, as there was significant transmission of E. coli cells from the product to the wash water (P < 0.001). When fresh-cut escarole was contaminated at a high inoculum level (5.1 log CFU/g), wash water quality influenced the level of cross-contamination, as the highest E. coli load (P < 0.001) was shown in uninoculated fresh-cut escarole washed with recirculated water. However, when fresh-cut escarole was contaminated at a low inoculum level (3.2 log CFU/g), the wash water quality did not influence the level of cross-contamination, as E. coli slightly increased, although not at a statistically significant level, after the uninoculated product was washed with recirculated water (P > 0.035). Therefore, the contamination level may impact the effectiveness of water quality to reduce pathogen concentrations. It was clearly observed that cross-contamination of fresh-cut escarole with E. coli occurs, thereby suggesting that small amounts of contamination could impact the overall product and indicating the necessity of using wash water sanitizers to eliminate pathogens.