Fresh-cut Iceberg Research Articles

Effects of hydroxyl radical on Listeria monocytogenes in fresh-cut iceberg lettuce (Lactuca sativa var. iceberg): Survival, membrane permeability, microstructure and virulence gene expression

Contamination of fresh-cut vegetables with Listeria monocytogenes is a food safety issue of particular concern. However, the inhibitory effect of hydroxyl radicals on Listeria monocytogenes in fresh-cut iceberg lettuce is not clear. This paper expounded the control effect and mechanism of hydroxyl radicals on Listeria monocytogenes in fresh-cut iceberg lettuce. Results showed that hydroxyl radicals (·OH) treated lettuce for 20 min could effectively inhibit the number of Listeria monocytogenes, and better maintain the sensory quality of fresh-cut lettuce. Hydroxyl radicals (·OH) increased cell membrane permeability and UV-absorbing substances by destroying the cell membrane integrity of Listeria monocytogenes; and attenuated the virulence of Listeria monocytogenes by down-regulating the expression of the virulence-related genes actA and recA; further affecting the survival and proliferation of Listeria monocytogenes in iceberg lettuce. This paper proposed an effective method to inhibit Listeria monocytogenes in fresh-cut lettuce, which will provide technical support and theoretical basis for its application in the fresh-cut lettuce industry.

Impact of surface dielectric barrier discharge cold atmospheric plasma on quality and stability of fresh-cut iceberg lettuce

This study evaluated the impact of cold atmospheric plasma (CAP) on fresh-cut iceberg lettuce (FIL) quality and stability. CAP treatments were performed using a Surface Dielectric Barrier Discharge, applying 6 kV at 23 kHz and exposition times varying from 15 to 60 min. FIL was analysed before and after treatments for polyphenoloxidase (PPO) and peroxidase (POD) activity, microbial contamination, colour, surface microstructure properties, chlorophylls content, polyphenols (TPC), ascorbic acid (AA), and antioxidant activity (AoA). TPC, AA and AoA were evaluated also after storage (4 °C for 5 days). CAP treatments provoked a reduction of PPO and POD activity with a processing time- and ozone-concentration-dependent effect. After treatments, a slight inactivation of mesophilic and psychrotrophic bacteria was observed, while yeast counts remained unaffected. With increasing treatment times, increasing cell damages and colour variations were detected, and a decrease of chlorophylls, TPC, AA, and AoA. After storage, an overall AoA increase was observed due to increased extractability or production by living cells of antioxidant compounds. These findings provide insights into the efficacy of CAP treatment in preserving fresh-cut iceberg lettuce quality. Further investigations are needed to optimize the process conditions and increase microbial inactivation while limiting qualitative damage to the product.

Addition of Fresh Herbs to Fresh-Cut Iceberg Lettuce: Impact on Quality and Storability

The aim of this study was to develop ready-to-eat vegetable–herb mixes with high nutritional and sensory values as well as good storability. In this regard, the suitability of fresh herbs (peppermint, oregano, green basil, red basil, and parsley) was tested for their use in mixes with fresh-cut iceberg lettuce. Lettuce–herb mixtures were stored for 6 days at 5 °C. The reason for the decrease in the appearance of the salads was the browning of the cut surface of the lettuce, as well as discoloration on the cut herbs. Comparing the storage abilities of the cut herbs, red basil and parsley retained the best appearance for 6 d at 5 °C. A small addition of herbs to fresh-cut iceberg lettuce caused a significant increase (p < 0.05) in the contents of pro-health ingredients such as chlorophyll, carotenoids, L-ascorbic acid, and polyphenols in the mixes. There were large discrepancies in the sensory quality of the mixes, but the highest quality and consumer acceptance were found for salads with parsley (5% and 10%) and red basil (5%). After harvest, the fresh herbs were more contaminated by molds than the iceberg lettuce. Bacterial, yeast, and mold contamination increased during storage, but the rate of mold growth was much lower in the mixes with parsley compared to lettuce alone. In conclusion, the addition of parsley and mint contributed the most to the health-promoting and microbiological properties of iceberg lettuce salads. However, according to sensory evaluation, parsley and red basil contributed the most to improving the acceptability of the product in terms of best taste and shelf life.

Untargeted volatolomic approach for the identification of sensory quality markers of fresh-cut iceberg lettuce stored in modified atmosphere packaging

Fresh-cut iceberg lettuce is appreciated by consumers for its nutritive properties, convenience, and ease of use. Producers are then pushed to preserve the quality of these products by using modified atmosphere packaging (MAP). In this study, the influence of passive MAP (air) or active MAP (1–5 % O2), on several quality attributes of fresh-cut iceberg lettuce samples was evaluated during storage time (from 3 to 14 d) at 4 °C. The respiration rate and the electrolyte leakage values of samples packaged in active MAP were higher than those of fresh-cut iceberg lettuce stored in the air, indicating stressful storage conditions. Inverse trends were observed for O-quinones content and browning index until the end of the storage period. Sensory analysis highlighted that active MAP has preserved the visual quality, limiting the browning of the cut surfaces. On the other hand, active MAP modified the sensory profile after 3 d at 4 °C, and samples scored below the marketability limit for both odor and off-odor. Finally, a volatile organic compound characterization by headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC–MS) allowed the identification of target molecules that could signal a decrease in food quality under different conditions. A total of 118 compounds were identified and, among them, ethyl alcohol and acetaldehyde were identified as the best quality markers for passive MAP and active MAP samples, respectively, while ethyl acetate could represent a good compromise to assess the quality of fresh-cut iceberg lettuce, regardless of MAP conditions.

Effect of low oxygen modified- and controlled-atmospheres on quality attributes and microbial population dynamics in fresh-cut iceberg lettuce

Effect of low oxygen modified- and controlled-atmospheres on quality attributes and microbial population dynamics in fresh-cut iceberg lettuce

Response of Fresh-Cut Iceberg Lettuce to Fumigation with Botanical Essential Oils

Abstract The study was conducted on iceberg lettuce ‘Ice Wave F1’. The effect of prestorage treatment with seven essential oils (EOs) of rosemary, peppermint, basil, thyme, marjoram, lemon, and oregano on the quality of cut lettuce was evaluated. The lettuce was fumigated with EOs for two hours in airtight containers. Two concentrations of EOs were used: 16.7 μL·L−1 and 33.3 μL·L−1. Fumigation with rosemary and thyme EOs lowered the browning of fresh-cut iceberg lettuce and thus the deterioration of its appearance during six days of storage. Lettuce fumigated with thyme EO scored relatively high in sensory quality and consumer acceptability. Lettuce fumigated with rosemary EO was characterized by high intensity of aroma and herbal flavor, significantly lowering its sensory rating. Marjoram EO at a dose of 16.7 μL·L−1 resulted in the fastest browning of lettuce cut surface and relatively reduced the market value during storage. Other EOs had no significant effect on the quality of cut lettuce during shelf life. It was also found that fumigation did not change bacteria, fungi, and mold populations on fresh-cut iceberg lettuce during short-term storage. The results obtained in the study showed that fumigation with thyme oil at a concentration of 33.3 μL·L−1 is most recommended for use in the storage of fresh-cut iceberg lettuce, but implementing these results into practice requires further research.

Prevalence and growth potential of Listeria monocytogenes in innovative, pre-packed, plant-based ready-to-eat food products on the Belgian market

In recent years, pre-packed ready-to-eat (RTE) food products on the Belgian market have shifted to a more plant-based composition due to a variety of reasons, including consumer concerns about health, animal welfare, and sustainability. However, similar to animal-based RTE foods, plant-based RTE foods can be susceptible to the presence and outgrowth of Listeria monocytogenes (L. monocytogenes). Three innovative, pre-packed, plant-based RTE food product categories on the Belgian market were identified based upon data gaps regarding the prevalence and growth potential of this pathogen. These were vegetarian and vegan deli sandwich slices (category 1), fresh-cut (mixes of) leafy vegetables (category 2), and multi-ingredient salad bowls (category 3). Reports on associated listeriosis outbreaks and recalls were collected and a comprehensive literature review on the prevalence of L. monocytogenes (i.e. detection in 25 g food) was performed. In addition, the prevalence of L. monocytogenes was also determined through an exploratory retail survey of ca. 50 different RTE products of each category. A batch was considered positive if L. monocytogenes was detected in a food item, either on the day of purchase, at the end of shelf life, or both. During the retail survey, L. monocytogenes was not detected in category 2 (0 out of 51 batches), while 1 out of 51 and 6 out of 48 batches were found positive for respectively category 1 and 3. The observed L. monocytogenes concentration did not exceed 10 CFU/g at any point in time in any batch. Furthermore, challenge tests were performed to determine the growth potential of L. monocytogenes in nine pre-packed, plant-based RTE food products (two to four different products of each category, and three different batches per product). After inoculation, products were stored for half of their shelf life at 7 °C and half of their shelf life at 9 °C (simulation of resp. retail and consumer storage). In six of the nine challenge tests executed, growth of L. monocytogenes was supported (i.e. growth potential ≥0.50 log10 CFU/g during shelf life). The highest growth potential was observed for fresh-cut iceberg lettuce (3.60 log10 CFU/g in 9 days), but a large variation regarding the growth potential of L. monocytogenes was noted both between and within the three studied pre-packed, plant-based RTE food product categories. This variation was mainly caused by differences in product composition, physicochemical product characteristics, present (competitive) microbiota such as lactic acid bacteria, applied preservation techniques, and shelf life.

Effects of Nano-Bentonite Polypropylene Nanocomposite Films and Modified Atmosphere Packaging on the Shelf Life of Fresh-Cut Iceberg Lettuce

In this study, the shelf life of fresh-cut iceberg lettuce (Lactuca sativa L.) was evaluated. Lettuce samples were washed with disinfectant agents and sodium hypochlorite and then soaked in an ascorbic acid solution. Next, samples were stored in packaging films containing three levels (1% and 3% and 0% as a control film) of nano-bentonite particles (NBPs) as a filler in a modified atmosphere for 12 days at 4 °C. Various physicochemical parameters such as color, texture, pH, titratable acidity, dehydration, moisture, dry matter, chlorophyll content, microbial quality, and sensory properties were investigated. Results indicated that nano-packaging had a significant ability to maintain the sensory physicochemical properties of lettuce at the fifth (1% nano-composite film) and ninth (3% nano-composite film) days of storage when compared to the control films. The greatest growths of molds and yeasts were observed in the control films, which demonstrates the effectiveness of the application of bentonite nanoparticle fillers.

Use of a silver-based sanitizer to accelerate Escherichia coli die-off on fresh-cut lettuce and maintain produce quality during cold storage: Laboratory and pilot-plant scale tests

Outbreaks and product recalls involving romaine and iceberg lettuce are frequently reported in the United States. Novel technologies are needed to inactivate pathogens without compromising product quality and shelf life. In this study, the effects of a process aid composed of silver dihydrogen citrate, glycerin, and lactic acid (SGL) on Escherichia coli and Listeria monocytogenes concentrations on lettuce immediately after washing and during cold storage were evaluated. Sensory and quality attributes of fresh-cut iceberg lettuce were also evaluated. Laboratory results indicated that application of SGL solution for 30 s as a first step in the washing process resulted in a 3.15 log reduction in E. coli O157:H7 immediately after washing. For E. coli O157:H7 a significant difference between SGL treatment and all other treatments was maintained until day 7. On day zero, SGL led to a 2.94 log reduction of L. monocytogenes. However, there was no significant difference between treatments with or without SGL regardless of storage time. Pilot-plant results showed that samples receiving SGL spray followed by chlorinated flume wash exhibited a greater reduction (1.48 log) in nonpathogenic E. coli populations at the end of shelf life than other treatments (p < 0.05). Additional pilot plant tests were conducted to investigate the hypothesis that SGL residues could continue to impact microbial survival on the final washed lettuce. Results show that pathogens introduced subsequent to flume washing of lettuce pretreated with SGL solution were not affected by antimicrobial residues. The final quality and shelf life of flume washed lettuce were also unaffected by pretreatment with SGL. In conclusion, the results of this study demonstrate that this new technology has the potential to accelerate E. coli die-off on fresh-cut lettuce during cold storage and improve product safety, while not affecting quality throughout the shelf life of the finished products.

The effect of wash water chlorine content on the pinking discolouration of fresh cut Iceberg lettuce

The effect of wash water chlorine content on the pinking discolouration of fresh cut Iceberg lettuce

The effect of wash water chlorine content on the pinking discolouration of fresh cut Iceberg lettuce

Processed Iceberg lettuce incurs high losses of up to 47% due to cut-edge pinking, despite modified atmosphere packaging (MAP) with nitrogen flushing to achieve low oxygen (<0.2%). Breeding for reduced pinking response is costly and not a short-term solution. Treatments including inhibitor additives and heat shock are not cost effective, whereas chlorine, already used as a sanitiser, has been proposed to reduce pinking. This study examined effects of applying chlorine to wash water at ≈1 mg L-1, 50 mg L-1, 100 mg L-1 and 200 mg L-1 total chlorine. Lettuce packaged in air exhibited a U-shaped response to chlorine, with minimum pinking score close to 100 mg L-1 chlorine. For cut lettuce stored under atmospheres to simulate MAP with nitrogen flushing to achieve different initial oxygen concentrations, 3% initial oxygen eliminated pinking, while with 6% lowest pinking scores were for lettuce washed at the highest chlorine concentration of 200 mg L-1.

Essential oil microemulsions inactivate antibiotic-resistant Salmonella Newport and spoilage bacterium Lactobacillus casei on Iceberg lettuce during 28-day storage at 4°C

The produce industry commonly uses chlorine to wash vegetables during post-harvest practices. However, chlorine has disadvantages because it is not sustainable to the environment, is not user-friendly, is corrosive to equipment, and loses efficacy in the presence of organic matter. Hence, alternatives to wash sanitizers are required to better meet the needs of the industry. Essential oil-based antimicrobial microemulsions in the wash water were evaluated for their efficacy against antibiotic-resistant Salmonella enterica serovar Newport and spoilage bacterium Lactobacillus casei on Iceberg lettuce. The microemulsions that were assessed included oregano oil, lemongrass oil, and cinnamon oil along with a plant-based emulsifier for improved solubility of the oil in water. Iceberg lettuce (10 g) was washed thoroughly and inoculated with Lactobacilli casei (6.0 log colony-forming units (CFU)/g) or Salmonella Newport (6.0 log CFU/g). The Iceberg leaves were separately treated with 0.1%, 0.3%, or 0.5% of the microemulsions, 50 ppm chlorine, and 3% hydrogen peroxide, stored at 4 °C, observed, and analyzed for surviving populations of both bacteria on days 0, 3, 7, 10, 14, 21, and 28. The efficacies of the antimicrobials were dependent on concentration and storage-time. The use of microemulsions resulted in a 2.3–4.37 log CFU/g reduction in the Salmonella population at various time points during days 0–28. They were also effective against Lactobacillus , resulting in 0.11–4.25 log CFU/g reduction during storage at days 0–28. The data on visual observation of treated leaves summarized in the tables and shown as figures indicated that the 0.1% oregano oil microemulsion had the best visual appeal in Iceberg leaves inoculated with S. Newport and the 0.5% lemongrass oil microemulsion showed improvement in reduced browning of the Iceberg leaves inoculated with Lactobacillus casei . This study demonstrates the potential of essential oil microemulsions to inactivate foodborne pathogenic and spoilage bacteria on Iceberg lettuce, thus providing effective produce decontamination strategies. • This study provides an innovative way to apply plant antimicrobials to leafy greens. • Essential oil microemulsions inactivated resistant Salmonella on Iceberg lettuce. • Microemulsions inhibited spoilage Lactobacillus growth allowing probiotic benefits. • Treated lettuce leaves showed reduced browning discoloration than untreated controls. • Microemulsions can serve as natural sanitizers on stored fresh-cut Iceberg lettuce.

The quality changes and shelf-life of fresh-cut Iceberg lettuce treated by ultrasound and modified atmosphere packages

ISHS IV International Conference on Fresh-Cut Produce: Maintaining Quality and Safety The quality changes and shelf-life of fresh-cut Iceberg lettuce treated by ultrasound and modified atmosphere packages

The quality changes and shelf-life of fresh-cut Iceberg lettuce treated by ultrasound and modified atmosphere packages

ISHS IV International Conference on Fresh-Cut Produce: Maintaining Quality and Safety The quality changes and shelf-life of fresh-cut Iceberg lettuce treated by ultrasound and modified atmosphere packages

High carbon-di-oxide modified atmospheric packaging on quality of ready-to-eat minimally processed fresh-cut iceberg lettuce

Fresh-cut lettuce is a very well-known salad for today's routines because it obliges minimal preparation to minimize the loss of health beneficial vitamins, minerals, antioxidants and other phytochemicals. It is a prodigious challenge to serve its consumers fresh. Quality of freshly processed lettuce under high CO2 modified atmosphere packaging (MAP) has been investigated as a realistic alternative technique for its preservation. Storage under high CO2 atmospheric treatments exhibited a significant impact in microbial development, electrolyte leakage, volatile metabolites and sensory quality of fresh-cut iceberg lettuce. This storage condition (MAP 1: 5 kPa O2 and 20 kPa CO2 balanced by N2 at 7 °C for 6 days) inhibited the growth of mesophilic bacteria and yeasts; delayed the enzymatic browning (cut-edges and intact surface) of fresh-cut iceberg lettuce and overall visual quality was also in acceptance limit. The development of off-odors was perceived in high CO2 MAP as a consequence of volatiles (ethanol and acetaldehyde) accumulation which was persisted at an inexcusable level during 6 days of storage periods.

Combined Effect of Dipping in Oxalic or in Citric Acid and Low O2 Modified Atmosphere, to Preserve the Quality of Fresh-Cut Lettuce during Storage.

Leaf edge browning is the main factor affecting fresh-cut lettuce marketability. Dipping in organic acids as well as the low O2 modified atmosphere packaging (MAP), can be used as anti-browning technologies. In the present research paper, the proper oxalic acid (OA) concentration, able to reduce respiration rate of fresh-cut iceberg lettuce, and the suitable packaging materials aimed to maintaining a low O2 during storage, were selected. Moreover, the combined effect of dipping (in OA or in citric acid) and packaging in low O2 was investigated during the storage of fresh-cut iceberg lettuce for 14 days. Results showed a significant effect of 5 mM OA on respiration rate delay. In addition, polypropylene/polyamide (PP/PA) was select as the most suitable packaging material to be used in low O2 MAP. Combining OA dipping with low O2 MAP using PP/PA as material, resulted able to reduce leaf edge browning, respiration rate, weight loss and electrolyte leakage, preserving the visual quality of fresh-cut lettuce until 8 days at 8 °C.

Modelling of the Behaviour of Salmonella enterica serovar Reading on Commercial Fresh-Cut Iceberg Lettuce Stored at Different Temperatures.

The aim of this study was to model the growth and survival behaviour of Salmonella Reading and endogenous lactic acid bacteria on fresh pre-cut iceberg lettuce stored under modified atmosphere packaging for 10 days at different temperatures (4, 8 and 15 °C). The Baranyi and Weibull models were satisfactorily fitted to describe microbial growth and survival behaviour, respectively. Results indicated that lactic acid bacteria (LAB) could grow at all storage temperatures, while S. Reading grew only at 15 °C. Specific growth rate values (μmax) for LAB ranged between 0.080 and 0.168 h−1 corresponding to the temperatures 4 and 15 °C while for S. Reading at 15 °C, μmax = 0.056 h−1. This result was compared with published predictive microbiology models for other Salmonella serovars in leafy greens, revealing that predictions from specific models could be valid for such a temperature, provided they were developed specifically in lettuce regardless of the type of serovars inoculated. The parameter delta obtained from the Weibull model for the pathogen was found to be 16.03 and 18.81 for 4 and 8 °C, respectively, indicating that the pathogen underwent larger reduction levels at lower temperatures (2.8 log10 decrease at 4 °C). These data suggest that this Salmonella serovar is especially sensitive to low temperatures, under the assayed conditions, while showcasing that a correct refrigeration could be an effective measure to control microbial risk in commercial packaged lettuce. Finally, the microbiological data and models from this study will be useful to consider more specifically the behaviour of S. Reading during transport and storage of fresh-cut lettuce, elucidating the contribution of this serovar to the risk by Salmonella in leafy green products.

Control of Listeria monocytogenes on ready-to-eat ham and fresh cut iceberg lettuce using a nisin containing Lactococcus lactis fermentate

Listeria monocytogenes is a potentially deadly psychrotrophic pathogen that can cause illness through contamination of ready-to-eat (RTE) foods. In this work we evaluated the use of a fermentate consisting of cells and supernatant of a nisin producing Lactococcus lactis strain to control L. monocytogenes in foods. In addition, to determine the role of nisin production in this activity, a transposon screen was carried out to isolate a nisin-negative mutant. Several independent mutants containing transposon insertions in the nisin gene cluster were obtained which exhibited a complete loss of anti-L. monocytogenes activity in an agar-based assay. A simple media using food grade components was found to support strong growth and nisin production of Lc. lactis 537 following incubation at between 20 and 35 °C. The ability of the fermentate to control L. monocytogenes in foods was evaluated in cut iceberg lettuce and RTE sliced ham stored at 4 °C for 10 days. Initial levels of 103–104 CFU/g L. monocytogenes were reduced to below detection limit (<20 CFU/g) immediately by the fermentate and remained so for the duration of the trial. In comparison, fermentate from the nisin-negative nisB mutant was unable to reduce L. monocytogenes levels initially. It did however provide some L. monocytogenes growth inhibition in ham and faster killing in lettuce at later time points, but not to undetectable levels. These results demonstrate that nisin containing fermentate provides a simple and effective means to control L. monocytogenes on RTE foods.

Enhancing produce safety: State estimation-based robust adaptive control of a produce wash system

The rapid introduction of fresh-cut produce into a produce wash system can dramatically decrease the free chlorine (FC) concentration level in the wash water, resulting in potential widespread cross-contamination throughout the entire wash system. To minimize such contamination, a sufficient level of FC must be maintained in the wash water. This paper presents a state estimation-based robust adaptive sliding mode (RASM) control strategy for the wash system to stabilize the FC concentration level during fresh-cut iceberg lettuce washing. This feedback control law for FC dosing is suggested to provide a sufficient FC injection rate (FCIR) to the wash system in order to compensate for the fall in the FC level and in turn to minimize the Escherichia coli (E. coli) O157:H7 levels on washed lettuce and in the wash water. The proposed controller uses the estimated chemical oxygen demand (COD) and FC concentration as feedback signals while system states are estimated by a hybrid extended Kalman filter (HEKF) and the unknown noise statistics are identified by a noise identification (NI) algorithm. Uniformly ultimately boundedness (UUB) of the FC concentration tracking error in the presence of unmodelled dynamics is proven using the Lyapunov framework and Barbalat’s lemma. The E. coli O157:H7 contamination levels are predicted from the joint estimator and controller properties. Simulation results show that the proposed NI-based HEKF/RASM control methodology achieves FC tracking while the pathogens converge to their predicted levels. The E. coli O157:H7 levels decrease as FC concentration increases and in particular, no E. coli O157:H7 is detected when FC concentration is regulated at 15 mg/L. Two robustness tests are performed to show the performance of the proposed controller in the presence of chlorine actuator failure and system parameter uncertainties. Finally, cross-contamination management is examined in terms of the prevalence and mean pathogen levels of incoming pre-wash lettuce in the context of FC regulation at 15 mg/L.

Modeling of Free Chlorine Consumption and Escherichia coli O157:H7 Cross-Contamination During Fresh-Cut Produce Wash Cycles.

Controlling the free chlorine (FC) availability in wash water during sanitization of fresh produce enhances our ability to reduce microbial levels and prevent cross-contamination. However, maintaining an ideal concentration of FC that could prevent the risk of contamination within the wash system is still a technical challenge in the industry, indicating the need to better understand wash water chemistry dynamics. Using bench-scale experiments and modeling approaches, we developed a comprehensive mathematical model to predict the FC concentration during fresh-cut produce wash processes for different lettuce types (romaine, iceberg, green leaf, and red leaf), carrots, and green cabbage as well as Escherichia coli O157:H7 cross-contamination during fresh-cut iceberg lettuce washing. Fresh-cut produce exudates, as measured by chemical oxygen demand (COD) levels, appear to be the primary source of consumption of FC in wash water, with an apparent reaction rate ranging from L/mg·min for all produce types tested, at stable pH levels (6.5 to 7.0) in the wash water. COD levels increased over time as more produce was washed and the lettuce type impacted the rate of increase in organic load. The model parameters from our experimental data were compared to those obtained from a pilot-plant scale study for lettuce, and similar reaction rate constant (5.38 × 10-4 L/mg·min) was noted, supporting our hypothesis that rise in COD is the main cause of consumption of FC levels in the wash water. We also identified that the bacterial transfer mechanism described by our model is robust relative to experimental scale and pathogen levels in the wash water. Finally, we proposed functions that quantify an upper bound on pathogen levels in the water and on cross-contaminated lettuce, indicating the maximum potential of water-mediated cross-contamination. Our model results could help indicate the limits of FC control to prevent cross-contamination during lettuce washing.