Ready-to-eat Salads Research Articles

Development of filtration-based RPA–CRISPR/Cas12a system for rapid, sensitive and visualized detection of Salmonella in ready-to-eat salads

Salmonella contamination of ready-to-eat (RTE) salads, a pathogen that causes foodborne diseases worldwide, continues to increase. Since RTE salads are consumed without any processing processes that remove pathogens, such as heat treatment, rapid and accurate testing is essential to effectively prevent such foodborne contamination. Therefore, in this study, I developed the recombinase polymerase amplification (RPA)–clustered regularly interspaced short palindromic repeats (CRISPR)/Cas12a system to amplify Salmonella gene (invA) in 20 min through RPA and visually detect it within 5 min using CRISPR/Cas12a. I successfully visually detected 101 CFU/mL of Salmonella pure culture using this system. Furthermore, for food sample preparation, I introduced the filtration based approach as a pretreatment method, which successfully reduced detection time and improved detection sensitivity. In conclusion, the developed filtration-based RPA CRISPR/Cas12a system enabled the visual detection of Salmonella in salads as low as 101 CFU/g. This system, which integrates filtration-based RPA-CRISPR/Cas12a, is a rapid, sensitive, and visually intuitive method for detecting Salmonella in RTE salads. It is also a useful technology with high applicability in POCT.

Leveraging Observations of Untrained Panelists to Screen for Quality of Fresh-Cut Romaine Lettuce

Fresh-cut romaine lettuce’s high perishability challenges ready-to-eat (RTE) salad production. Selecting cultivars less prone to browning and decay is crucial for extending shelf life. Traditional quality evaluation methods using instrumentation and trained panelists are time-consuming and logistically complex. This study investigated the effectiveness of untrained volunteers in assessing fresh-cut romaine lettuce quality. Given that the average consumer in the USA is familiar with the flavor characteristics of romaine lettuce, this study proposed to investigate the value of having untrained volunteers discern the quality of fresh-cut romaine lettuce. Therefore, six romaine lettuce accessions (Green Forest, King Henry, Parris Island Cos, PI 491224, SM13-R2, and Sun Valley) were assessed for sensory quality attributes (browning, green color, decay, and overall quality) and compared with instrumentation analyses (gas composition including O2 and CO2, electrolyte leakage, and color). The results showed significant quality differences (p < 0.05) among the accessions, with some seasonal variability. Very importantly, the consumers’ (n = 159) assessments revealed similar results to those produced by either instrumentation or a trained panel. The consumers provided sensory scores that allowed for the grouping of accessions based on their postharvest quality, which efficiently matched their pedigree relationship. In conclusion, ad hoc consumer panels can be an effective way to characterize the quality of romaine lettuce for RTE salads.

Monitoring the Bioprotective Potential of Lactiplantibacillus pentosus Culture on Pathogen Survival and the Shelf-Life of Fresh Ready-to-Eat Salads Stored under Modified Atmosphere Packaging.

Globally, fresh vegetables or minimally processed salads have been implicated in several foodborne disease outbreaks. This work studied the effect of Lactiplantibacillus pentosus FMCC-B281 cells (F) and its supernatant (S) on spoilage and on the fate of Listeria monocytogenes and Escherichia coli O157:H7 on fresh-cut ready-to-eat (RTE) salads during storage. Also, Fourier transform infrared (FTIR) and multispectral imaging (MSI) analysis were used as rapid and non-destructive techniques to estimate the microbiological status of the samples. Fresh romaine lettuce, rocket cabbage, and white cabbage were used in the present study and were inoculated with L. pentosus and the two pathogens. The strains were grown at 37 °C for 24 h in MRS and BHI broths, respectively, and then were centrifuged to collect the supernatant and the pellet (cells). Cells (F, ~5 log CFU/g), the supernatant (S), and a control (C, broth) were used to spray the leaves of each fresh vegetable that had been previously contaminated (sprayed) with the pathogen (3 log CFU/g). Subsequently, the salads were packed under modified atmosphere packaging (10%CO2/10%O2/80%N2) and stored at 4 and 10 °C until spoilage. During storage, microbiological counts and pH were monitored in parallel with FTIR and MSI analyses. The results showed that during storage, the population of the pathogens increased for lettuce and rocket independent of the treatment. For cabbage, pathogen populations remained stable throughout storage. Regarding the spoilage microbiota, the Pseudomonas population was lower in the F samples, while no differences in the populations of Enterobacteriaceae and yeasts/molds were observed for the C, F, and S samples stored at 4 °C. According to sensory evaluation, the shelf-life was shorter for the control samples in contrast to the S and F samples, where their shelf-life was elongated by 1-2 days. Initial pH values were ca. 6.0 for the three leafy vegetables. An increase in the pH of ca. 0.5 values was recorded until the end of storage at both temperatures for all cases of leafy vegetables. FTIR and MSI analyses did not satisfactorily lead to the estimation of the microbiological quality of salads. In conclusion, the applied bioprotective strain (L. pentosus) can elongate the shelf-life of the RTE salads without an effect on pathogen growth.

Moving towards on-site detection of Shiga toxin-producing Escherichia coli in ready-to-eat leafy greens

Rapid identification of Shiga toxin-producing Escherichia coli, or STEC, is of utmost importance to assure the innocuousness of the foodstuffs. STEC have been implicated in outbreaks associated with different types of foods however, among them, ready-to-eat (RTE) vegetables are particularly problematic as they are consumed raw, and are rich in compounds that inhibit DNA-based detection methods such as qPCR. In the present study a novel method based on Loop-mediated isothermal amplification (LAMP) to overcome the limitations associated with current molecular methods for the detection of STEC in RTE vegetables targeting stx1 and stx2 genes. In this sense, LAMP demonstrated to be more robust against inhibitory substances in food. In this study, a comprehensive enrichment protocol was combined with four inexpensive DNA extraction protocols. The one based on silica purification enhanced the performance of the method, therefore it was selected for its implementation in the final method. Additionally, three different detection chemistries were compared, namely real-time fluorescence detection, and two end-point colorimetric strategies, one based on the addition of SYBR Green, and the other based on a commercial colorimetric master mix. After optimization, all three chemistries demonstrated suitable for the detection of STEC in spiked RTE salad samples, as it was possible to reach a LOD50 of 0.9, 1.4, and 7.0 CFU/25 g for the real-time, SYBR and CC LAMP assays respectively. All the performance parameters reached values higher than 90 %, when compared to a reference method based on multiplex qPCR. More specifically, the analytical sensitivity was 100, 90.0 and 100 % for real-time, SYBR and CC LAMP respectively, the specificity 100 % for all three assays, and accuracy 100, 96 and 100 %. Finally, a high degree of concordance was also obtained (1, 0.92 and 1 respectively). Considering the current technological advances, the method reported, using any of the three detection strategies, demonstrated suitable for their implementation in decentralized settings, with low equipment resources.

ASSESSMENT OF HEAVY METALS IN READY-TO-EAT (RTE) VEGETABLES SALADS SOLD WITHIN KANO METROPOLIS, NIGERIA

Ready-to-eat (RTE) salads prepared from leafy vegetables sold in the streets are now common in Kano metropolis due to their convenience and acceptance by consumers. Due to the unhygienic environmental conditions and other condiments used in its preparation, vegetable salad could be contaminated with heavy metals. This study aimed to determine heavy metals safety of RTE salads hawked in Kano metropolis, Kano state, Nigeria. Forty samples of RTE salads were purposely purchase from eight local government areas of Kano metropolis and were analyzed for the presence of Cd, Cr, Hg and Pb using Atomic Absorption Spectrophotometer. The results of the analysis showed the concentration of Hg (3.208 - 1.220 mg/kg), Cr (0.756 - 0.212 mg/kg), Pb (0.392 - 0.036 mg/kg) and Cd (0.056 - 0.044). It was therefore concluded that vegetable salad sold in Kano metropolis are prone to public health concerns since the levels of Hg, Cr and Pb were found to be above the permissible limits of 0.01, 0.1 and 0.1 (for leafy vegetables) ratified by the Codex Alimentarius Commission. Thus, prevention of heavy metals contamination in vegetables salads is necessary, this will help in prevention of acute and chronic health problems due to exposure to heavy metals from consuming street vended RTE vegetables salads in this region.

Assessment of the presence of Acinetobacter spp. resistant to β-lactams in commercial ready-to-eat salad samples

Acinetobacter baumannii is a well-known nosocomial infection causing agent. However, other Acinetobacter spp. have also been implicated in cases of human infection. Additionally, these bacteria are known for the development of antibiotic resistance thus making the treatment of the infections they cause, challenging. Due to their relevance in clinical setups less attention has been paid to their presence in foods, and its relation with infection/dissemination routes. In the current study commercial Ready-To-Eat (RTE) salads were analyzed seeking for antibiotic resistant Acinetobacter spp. A preliminary screening allowed us to recover Gram-negative bacteria resistant to β – lactams using cefotaxime, third generation cephalosporins, as the selective agent, and this was followed by identification with CHROMagar™ Acinetobacter and 16S rDNA sequencing. Finally, the isolates identified as Acinetobacter spp. were reanalyzed by PCR to determine the presence of nine potential Extended Spectrum β Lactamases (ESBL). Two commercial RTE salad brands were included in the study (2 batches per brand and 8 samples of each batch making a total of 32 independent samples), and compared against an organic lettuce. High concentrations of β – lactam, resistant bacteria were found in all the samples tested (5 log CFU/g). Additionally, 209 isolates were phenotypically characterized on CHROMagar Acinetobacter. Finally, PCR analysis identified the presence of different ESBL genes, being positive for blaACC, blaSHV, blaDHA and blaVEB; out of these, blaACC was the most prevalent. None of the isolates screened were positive for more than one gene. To conclude, it is important to highlight the fact that pathogenic species within the genus Acinetobacter spp., other than A. baumannii, have been identified bearing resistance genes not typically associated to these microorganisms highlight the importance of continuous surveillance.

UVB treatments of packaged ready-to-eat salads: Induced enhancement of quercetin derivatives in baby-leaf lettuce (Lactuca sativa L.) and wild rocket (Diplotaxis tenuifolia L.)

Ready-To-Eat (RTE) salads conveniently pre-prepared in bags can promote the intake of natural bioactive compounds, including antivirals such as quercetin. However, the content of these compounds in the species used for RTE salads is usually low due to limited solar UV exposure under tunnels and greenhouses in which they are usually cultivated. To address this, we treated commercial fresh-cut lettuce (Lactuca sativa L.) and wild rocket (Diplotaxis tenuifolia L.) leaves using a narrow-band UVB lamp directly through sealed polypropylene bags during storage (5–6 °C, 80% RH). The bagged leaf samples were kept under 20 µmol m−2 s−1 of white light with a 12 h photoperiod for 6 d. Half of the samples were additionally treated, 9 h d−1, during the first 3 d by UVB narrow-band lamps delivering 2.8–3.6 μmol m−2s−1 of UVB and 0.8–1.0 μmol m−2s−1 of UVA radiation. The effects of the UVB treatments on epidermal phenolics, chlorophyll and photosynthetic parameters were monitored daily by non-destructive fluorescence sensors over a 6-d storage period. At the end of the experiment, destructive HPLC-DAD analysis of phenolics and photosynthetic pigments, antioxidant capacity assays and fresh weight loss determinations were conducted. The UVB-treatment increased the epidermal phenolics (EPhen) Index with respect to unirradiated controls, while not affecting chlorophyll and carotenoids levels as well as photosynthetic efficiency. For both species, the EPhen Index changes were detected 15 h after the first UVB application. Then, wild rocket responded faster than baby-leaf lettuce and reached the maximal phenolic level with less than 1/3 of the energy dose needed by lettuce. UVB-treated samples exhibited higher flavonoid concentrations (mainly quercetin derivatives) compared to controls (48–67% and 37–66% in lettuce and wild rocket, respectively). Leaf chlorophyll and carotenoid contents were not affected by both UVB treatment and storage. We proved, for the first time, that it is possible to treat RTE salad leaves using through-packaging UVB radiation and enhance their total phenolic and quercetin derivative contents. We also provided more insights concerning the dynamics of the UVB-elicitation of phenolic compounds in postharvest leaves. Our results are propaedeutic for the optimization of potential UVB-treatments; selection of the most efficient wavelengths, intensity, single/multiple doses and proposals for application in the food industry.

Prevalence of multiple-drug resistance and identification of underlying antibiotic resistance genes in Escherichia coli isolated from ready-to-eat chicken salads being sold in restaurants in Delhi, India

Antibiotic resistance (AR) is a quintessential one-health concern. Unregulated usage of antibiotics in human clinical and veterinary sector has exacerbated the global figures of morbidity and mortality. One of the reasons behind clinical manifestation of AR is the farm-to-fork movement of AR bacteria (ARB), which necessitates a systematic evaluation of food products for AR-related threats. Due to easier availability, claimed high nutritional value and cost effectiveness, meat-based ready-to-eat (RTE) salads are gaining popularity among the consumers in low-and middle-income countries (LMICs) like India. Nevertheless, it has not yet been followed by a stern microbial evaluation concerning AR. Our study acknowledges this gap by performing a systematic evaluation of AR profile of a sentinel opportunist, Escherichia coli associated with chicken based RTE salads being served in popular restaurants in Delhi, India; and identifying the antibiotic resistance genes (ARGs) that drive the observed resistance. Results showed a significant degree of resistance in E. coli isolates to nalidixic-acid (35.89%), tetracycline (35.0%), β-lactams [ampicillin (28.3%), amoxicillin-clavulanic acid (26%), imipenem (25%)], and fluoroquinolones [ciprofloxacin (22.5%), norfloxacin (20.83%)], among others. Upon screening the isolates for the presence of 22 ARGs, genes like qnrS (42.5%), tetA (40.83%), strB (20%), aadA1(12.5%), qnrA (12.5%) and strA (11.66%) were prevalent. Multiple drug resistance (MDR) was showcased by 29.17% isolates while multiple ARGs were harboured by 25.83% of the screened isolates. Due to the well-known association of the prevalent ARGs with plasmids and mobile genetic elements (MGEs) in our study, our results present a concerning scenario where the manifestation of AR in humans is possible through meat-based RTE salads.

Molecular Characterization of Microbial Quality of Ready-to-eat Salads using Multi-locus Sequence Typing

Uncertainty persists concerning the role of ready-to-eat (RTE) salad as a bacterial reservoir. The attention paid to food safety by international agencies and international regulations has not improved food safety despite technological advancements, RTE salad’s microbiological quality and safety still seems challenging. The present study’s objective was to detect any microorganism in the RTE salads sold in supermarkets of Riyadh, Saudi Arabia, and to interpret the susceptibility pattern of isolated bacteria to a set of antimicrobials. Phenotypic methods and biochemical analysis were used to identify the isolated bacterium from each salad sample. Antibiograms of the isolated bacteria was determined by VITEK system 2. Multi-locus sequence typing (MLST) was performed for 15 Escherichia coli isolates for investigating evolutionary relationship and genetic analysis. The culture-based technique showed that the major species identified in samples were Aeromonas spp., Acinetobacter spp., E. coli, Roultella ornithinolytica, Citrobacter koseri, Luciferciaadec arboxylata, Klebsiella oxytoca, and Aerococcus viridians. Remarkably, Acinetobacter spp. showed the highest antibiotic resistance to erythromycin, nitrofurantoin and co-trimoxazole. ST 1887 was the most common one traced in 3 E. coli isolates, when total of 12 STs (sequence types) were specified to 15 isolates. A total of three clonal complexes (CC); CC-12, CC-14 & CC-23 were reported in this study. Implementing an accurate, rapid, and easy microbiological analysis method could be valuable for providing higher quality products. Based on the obtained results, dedicated regular RTE salad quality monitoring is recommended, and hand hygiene should be maintained while handling and packaging of RTE.

Multidrug-resistant extended spectrum β-lactamase (ESBL)-producing Escherichia coli from farm produce and agricultural environments in Edo State, Nigeria.

Antimicrobial resistance (AMR) is a major public health concern, especially the extended-spectrum β-lactamase-producing (ESBL) Escherichia coli bacteria are emerging as a global human health hazard. This study characterized extended-spectrum β-lactamase Escherichia coli (ESBL-E. coli) isolates from farm sources and open markets in Edo State, Nigeria. A total of 254 samples were obtained in Edo State and included representatives from agricultural farms (soil, manure, irrigation water) and vegetables from open markets, which included ready-to-eat (RTE) salads and vegetables which could potentially be consumed uncooked. Samples were culturally tested for the ESBL phenotype using ESBL selective media, and isolates were further identified and characterized via polymerase chain reaction (PCR) for β-lactamase and other antibiotic resistance determinants. ESBL E. coli strains isolated from agricultural farms included 68% (17/25) from the soil, 84% (21/25) from manure and 28% (7/25) from irrigation water and 24.4% (19/78) from vegetables. ESBL E. coli were also isolated from RTE salads at 20% (12/60) and vegetables obtained from vendors and open markets at 36.6% (15/41). A total of 64 E. coli isolates were identified using PCR. Upon further characterization, 85.9% (55/64) of the isolates were resistant to ≥ 3 and ≤ 7 antimicrobial classes, which allows for characterizing these as being multidrug-resistant. The MDR isolates from this study harboured ≥1 and ≤5 AMR determinants. The MDR isolates also harboured ≥1 and ≤3 beta-lactamase genes. Findings from this study showed that fresh vegetables and salads could be contaminated with ESBL-E. coli, particularly fresh produce from farms that use untreated water for irrigation. Appropriate measures, including improving irrigation water quality and agricultural practices, need to be implemented, and global regulatory guiding principles are crucial to ensure public health and consumer safety.

Nutritional Assessment of Ready-to-Eat Salads in German Supermarkets: Comparison of the nutriRECIPE-Index and the Nutri-Score.

Globally, an unbalanced diet causes more deaths than any other factor. Due to a lack of knowledge, it is difficult for consumers to select healthy foods at the point of sale. Although different front-of-pack labeling schemes exist, their informative value is limited due to small sets of considered parameters and lacking information on ingredient composition. We developed and evalauated a manufacture-independent approach to quantify ingredient composition of 294 ready-to eat salads (distinguished into 73 subgroups) as test set. Nutritional quality was assessed by the nutriRECIPE-Index and compared to the Nutri-Score. The nutriRECIPE-Index comprises the calculation of energy-adjusted nutrient density of 16 desirable and three undesirable nutrients, which are weighted according to their degree of supply in the population. We show that the nutriRECIPE-Index has stronger discriminatory power compared to the Nutri-Score and discriminates as well or even better in 63 out of the 73 subgroups. This was evident in groups where seemingly similar products were compared, e.g., potato salads (Nutri-Score: C only, nutriRECIPE-Index: B, C and D). Moreover, the nutriRECIPE-Index is adjustable to any target population's specific needs and supply situation, such as seniors, and children. Hence, a more sophisticated distinction between single food products is possible using the nutriRECIPE-Index.

Quantitative risk assessment model to investigate the public health impact of varying Listeria monocytogenes allowable levels in different food commodities: A retrospective analysis

Invasive listeriosis is a potentially fatal foodborne disease that according to this study may affect up to 32.9 % of the US population considered as increased risk and including people with underlying conditions and co-morbidities. Listeria monocytogenes has been scrutinized in research and surveillance programs worldwide in Ready-to-Eat (RTE) food commodities (RTE salads, deli meats, soft/semi-soft cheese, seafood) and frozen vegetables in the last 30 years with an estimated overall prevalence of 1.4–9.9 % worldwide (WD) and 0.5–3.8 % in the United States (US). Current L. monocytogenes control efforts have led to a prevalence reduction in the last 5 years of 4.9–62.9 % (WD) and 12.4–92.7 % (US). A quantitative risk assessment model was developed, estimating the probability of infection in the US susceptible population to be 10–10,000× higher than general population and the total number of estimated cases in the US was 1044 and 2089 cases by using the FAO/WHO and Pouillot dose-response models. Most cases were attributed to deli meats (>90 % of cases) followed by RTE salads (3.9–4.5 %), soft and semi-soft cheese and RTE seafood (0.5–1.0 %) and frozen vegetables (0.2–0.3 %). Cases attributed to the increased risk population corresponded to 96.6–98.0 % of the total cases with the highly susceptible population responsible for 46.9–80.1 % of the cases. Removing product lots with a concentration higher than 1 CFU/g reduced the prevalence of contamination by 15.7–88.3 % and number of cases by 55.9–100 %. Introducing lot-by-lot testing and defining allowable quantitative regulatory limits for low-risk RTE commodities may reduce the public health impact of L. monocytogenes and improve the availability of enumeration data.

Isolation, identification, and antibiogram studies of Escherichia coli from ready-to-eat foods in Mymensingh, Bangladesh.

Background and Aim:Ready-to-eat (RTE) foods are widely used at home, restaurants, and during festivals in Bangladesh. So it is very important to investigate possible microbial contamination in RTE foods. Therefore, this study aimed to determine the total coliform count (TCC), isolate, identify, and characterize the Escherichia coli in RTE foods. The antimicrobial sensitivity of E. coli obtained from RTE foods was also performed using 12 commonly used antibiotics.Materials and Methods:A total of 100 RTE food samples were collected aseptically and comprised of ten samples each: Burger, pizza, sandwich, chicken roll, chicken meat loaf, chicken fry, salad vegetable, ice-cream, yogurt, and milkshake sold in Mymensingh City. Samples were inoculated onto Eosin methylene blue agar and incubated at 37°C for 24 h. Isolation and identification of bacteria were performed based on cultural, staining, and biochemical properties, followed by a polymerase chain reaction.Results:The TCC in Chicken meat loaf, burger, pizza, sandwich, salad vegetable ice-cream, and yogurt samples were 3.57 ± 0.96, 3.69 ± 0.08, 3.50 ± 0.60, 2.60 ± 0.20, 4.09 ± 0.29, 4.44 ± 0.25, and 3.14 ± 0.30 mean log colony-forming units ± standard deviation/mL, respectively. The study found a higher prevalence of E. coli in RTE salad vegetable products than in RTE meat and milk products. Forty percent of the mixed vegetable salad samples showed positive results for E. coli. Whereas E. coli prevalence in RTE meat and milk products was 20% and 16.7%, respectively. All the 21 isolates were subjected to antibiotic susceptibility test against 12 different antibiotics. It was observed that 46.1% were susceptible, 16.6% were intermediate, 46.1% were resistant, and 47.6% were multidrug-resistant (MDR) among seven different antibiotic classes. E. coli isolates were resistant to cephalexin, ceftazidime, oxytetracycline, and ampicillin and sensitive to gentamycin, followed by kanamycin, ceftriaxone, colistin, and enrofloxacin.Conclusion:The study revealed that RTE foods are a serious issue from a public health point of view. To achieve a safer level of E. coli in RTE foods sold for human consumption, public food outlets must improve hygienic and good production procedures. Moreover, MDR E. coli in these foods pose serious public health threats.

Growth potential of Salmonella enterica in thirty‐four different RTE vegetable salads during shelf‐life

SummaryThirty‐four different ready‐to eat (RTE) vegetable salads were inoculated with a cocktail of three Salmonella enterica strains, and stored under a modified atmosphere for up to 168 h at 4, 7, 12 and 16°C. Eighteen (18) of the salad samples comprised of two or more vegetable ingredients (also referred to as MV RTE salads), and 16 were made up of single vegetable ingredients (SV RTE salads). Generally, the growth potential of inoculated S. enterica varied depending on temperature and type of RTE vegetable salad. The higher temperature was generally more favourable for the growth of S. enterica. Among all 34 salad samples, 5, 11, 18 and 24 salad samples supported the growth of Salmonella at 4, 7, 12 and 16°C, respectively. All salads consisting of multiple vegetable ingredients except two: one comprised of carrots, lettuce and beetroot and another comprised of white cabbage and purple cabbage, supported the growth of Salmonella at high temperatures (either 12 or 16 or both 12 and 16°C). Although the growth of Salmonella was variable in the different types of RTE salads, and growth was generally low at 4°C, Salmonella exhibited consistently minimal growth in some vegetable salads such as those comprised of carrots, lettuce and beetroot, carrots, beetroots, cabbage and cucumber, as well as one comprised of beetroot and corn at all temperature conditions tested.

Risk and socio-economic impact for Staphylococcus aureus foodborne illness by ready-to-eat salad consumption

Microbial risk assessment is a valuable tool to provide scientific evidence to control food safety. Therefore, this study evaluated the risk of foodborne illness caused by Staphylococcus aureus in ready-to-eat (RTE) salad products and economic impact. The prevalence of S. aureus in salads, the RTE salad consumption, and distribution conditions (time and temperature) in market parameters were determined, and the data were analysed using the @RISK program to determine the appropriate probabilistic distribution. Predictive models were developed to describe the fate of S. aureus under distribution conditions. A simulation model was prepared with the collected data to calculate the risk of illness per person per day, and this risk was used to calculate the economic impact. S. aureus was detected in 2% of RTE salads, and the initial contamination level was calculated using the Beta distribution. Baranyi model was used to calculate the maximum specific growth rate (μmax), lag phase duration (LPD), and the secondary models well described the temperature effect on LPD and μmax with R2 values of 0.973–0.979. Also, the root mean square error values of 0.362 suggested that the model performance was appropriate. Lognormal distribution estimated that the average daily consumption amount and ratio was 137.7 g and 9.8%, respectively. The simulation model showed that the average probability of S. aureus foodborne illness following RTE salad consumption was 2.1 × 10−9 per person per day. The probability was used to estimate the socio-economic burden, and the annual socio-economic cost was calculated as $48,343.

Food safety inspection of tas kebab and salad processing line in a catering company

This study was conducted to evaluate the sufficiency of food safety practices in a catering company. The presence of some pathogenic and indicator bacteria was monitored in the samples collected from raw materials, food, food contact surfaces and workers' hands and various steps of the tas kebab (a Turkish meat stew) and salad processing lines. Bacillus cereus was found in ready-to-eat (RTE) tas kebab and RTE salad, while Listeria monocytogenes was isolated from RTE salad. Furthermore, it was observed that RTE salad contained coagulase-positive Staphylococcus aureus without staphylococcal enterotoxin production. The swab samples obtained from cutting board surfaces, knives and workers' hands contained high counts of total aerobic bacteria and some samples were contaminated with coliforms and coagulase-positive/negative staphylococci. The presence of B. cereus and L. monocytogenes in RTE foods is a serious threat to public health, especially in the catering business. Preventing the presence of toxin-producing bacteria in RTE food is a fundamental action. Also, the occurrence of L. monocytogenes in RTE salad and B. cereus in RTE tas kebab/salad samples showed insufficient cleaning/disinfection practices. As a result, hygiene practices and regular monitoring in the catering business are necessary for food safety.

Ready-to-eat salads and berry fruits purchased in Italy contaminated by Cryptosporidium spp., Giardia duodenalis, and Entamoeba histolytica

Ready-to-eat (RTE) salads and berries are increasingly consumed in industrialized countries. These products can be contaminated by pathogenic parasites that have been responsible for foodborne outbreaks worldwide. In Italy, there are few data on contamination of RTE salads and berries with parasite transmission stages and this requires more-in-depth investigations. To estimate the prevalence of contamination with Cryptosporidium spp. and Giardia duodenalis in these fresh products, a total of 324 packages of local RTE mixed salads - belonging to three different industrial brands – and 324 packages of berries - blueberries from Peru, blackberries from Mexico, raspberries from Italy - were bought from supermarkets located in the Provinces of Bari and Foggia, Apulia, Italy. A pool size of nine packages was chosen and a total of 72 pools were processed in the whole year. After washing, the pellets were examined by microscopy (FLOTAC) and tested using conventional simplex PCR, targeting Cryptosporidium spp., Giardia duodenalis, and Entamoeba spp., and sequencing. Several Cryptosporidium species and Giardia duodenalis assemblages, some of which are of potential zoonotic relevance, as well as Entamoeba spp., were identified in both matrices. By microscopy, Giardia-like cysts in local raspberries and Entamoeba-like cysts in imported blueberries were detected. Giardia duodenalis (Assemblages A, B and E) and Entamoeba histolytica were molecularly confirmed with overall prevalences of 4.6% (95% C.I. 3.0–6.8) and 1% (95% C.I. 0.3–2.1), respectively. Molecular methods identified Cryptosporidium ryanae, Cryptosporidium bovis, Cryptosporidium xiaoi, and Cryptosporidium ubiquitum in both matrices, with a prevalence of 5.1% (95% C.I. 3.3–7.3). A distinct seasonality in prevalence was observed for G. duodenalis, with most positives occurring in spring, whereas Cryptosporidium showed no significant seasonal variations. These results highlight that inadequate management of fresh produce, both locally produced and imported, along the food chain may have the potential for consequences on human health.

Heavy metals safety of Ready-To-Eat (RTE) vegetables salads (a review)

Vegetables are one of the classes of foods that importantly contribute to the whole health and wellbeing of its consumers. It benefits the human body with important nutrients and help in reducing kind of chronic diseases. Ready-to-eat (RTE) foods are generally becoming more popular even in the developing world due to change in lifestyles. One of the most usually RTE food consumed in the northern Nigeria is road side salad that is arranged with vegetables usually lettuce (Lactuca sativa L.), cabbage (Brassica oleracea var. capitata) or Cress (Lepidium sativum Linn.) as the main components with the addition of tomato, onion and carrot. However, the consumption of RTE foods promote severe safety threats as vegetables prove well-known trace element and heavy metals (HMs) some of which are essential for good health while some are toxic. HMs include lead (Pb), cadmium (Cd), zinc (Zn), mercury (Hg), arsenic (As), silver (Ag), chromium (Cr), copper (Cu), iron (Fe), and platinum (Pt). Different sources through which vegetables can be contaminated with these HMs are natural sources, agricultural sources, industrial sources, domestic effluent, atmospheric sources and other sources. Ingestion of vegetables containing HMs is one of the major means in which these elements enter human body. Once entered, HMs is dumped in bone and fat tissues, overlapping noble minerals. Slowly released into the body, HMs can cause an array of diseases. Thus, the essence of this study is to review the safety of the RTE vegetable salads, assessing the contamination level of some dangerous HMs present. As RTE salads can be contaminated with different types HMs that makes them unsafe for human consumption, regulatory bodies should design a periodic workshop training for RTE foods hawkers to help fix the problems and enhance the effectiveness of RTE vegetables salads preparation. Public awareness on the serious health risk associated with mishandled prepared insignificantly processed RTE foods most especially vegetable salads should be considered.

A review on microbiological safety of Ready-To-Eat Salads

Eating of road side ready-to-eat (RTE) salads that is made with green leafy vegetables (GLVs) commonly lettuce (Lactuca sativa L.), cabbage (Brassica oleracea var. capitata) or Cress (Lepidium sativum Linn.) as the key constituents coupled with adding tomatoes, sliced onions, cucumber, groundnut cake and so on has been reported to cause severe safety threats owing to its being extremely disposed to microbiologically inclined contamination, thereby leading to a public health issue. Pathogenic microorganisms pollute salads as a result of mishandling of raw vegetables, during preparation of salads and also associated environment. Soils typically harbor abundant microorganisms, some of which are human pathogens such as B. cereus, Clostridium botulinum, C. perfringens, Listeria monocytogenes and Aeromonas. Birds are carriers of pathogens such as E. coli O157:H7, Salmonella and Campylobacter. Reptiles and arthropods are usually in cultivation fields, and therefore have unrestricted access to produce and many bacterial species have evolved to exploit these animals as hosts or vectors. Insect deterioration creates openings that aid the ingress of pathogens into inner plant tissues, thereby enhancing colonization of spoilage and pathogenic bacteria on produce. Not only animals, similarly people working with the vegetables produce are known to be a source and direct contact vector of microorganisms. Hence this type of food is regarded as potential vehicles of food borne illnesses resulting in large and serious national and international outbreaks. Thus, the essence of this study is to review the safety of the RTE vegetable salads, assessing the contamination level of the most prevalent pathogenic microorganisms. RTE salads can be contaminated with different types of foodborne pathogens from farm-to-fork that makes them unsafe for human consumption. Regulatory bodies should design periodic workshop training for RTE food hawkers to help fix the problems and enhance the effectiveness of RTE vegetables salads preparation. Public awareness on the serious health risk associated with mishandled or poorly prepared minimally processed RTE foods most especially vegetable salads should be considered.

Antimicrobial activity of lime oil in the vapour phase against Listeria monocytogenes on ready-to-eat salad during cold storage and its possible mode of action

This study investigated the antimicrobial activity of lime oil (LO) at 50, 100, and 200 μl to control microbial spoilage and the survival of Listeria monocytogenes on ready-to-eat (RTE) mixed vegetable salads in 1-L glass boxes for 7 days in a refrigerator (~4 °C). The bacteriostatic properties of L. monocytogenes were investigated by cell constituent release analysis and crystal violet assays, which are related to the bacterial cell wall and cell membrane. Scanning electron microscopy (SEM) was used to study the morphology of L. Monocytogenes, and the components of LO in treated RTE mixed vegetable salads using were studied by gas chromatography-mass spectrometry (GC-MS). The results indicated that LO at 100 μl L−1 could inhibit cell cultures and reduce the growth of L. monocytogenes (⁓104 cfu ml−1) on RTE salads in refrigerated conditions by 0.6–1.5 log10 cfu g−1. The results revealed that LO affected bacterial cell permeability and cell membrane integrity. The treated cells showed serious detrimental defects in their membrane morphology. Furthermore, α-terpineol, terpineol and limonene were confirmed as the key components that inhibited bacteria during cold storage. The quality of RTE salads stored with LO in a 1-L glass box showed good results, and the consumers also accepted the salads with a hedonic score (~6.1 ± 0.7) rated as ‘like slightly’ for sensory evaluation.