Prevalence and counts of Salmonella spp. in minimally processed vegetables in São Paulo, Brazil

Investigating processing practices and microbiological quality of minimally processed vegetables in Brazil

Minimally processed vegetables (MPVs) are marketed as convenient and healthy choices for consumers. However, the absence of post-commercialization treatments raises concerns about their microbiological safety. This study investigated the processing practices of 28 Brazilian MPV plants and compared the microbiological quality of these products with fresh counterparts in the city of Sao Paulo, Brazil. Through cluster analysis, the processing plants were categorized into two groups: group 1 (nineteen plants) primarily uses chemical substances in the washing step, while group 2 (nine plants) avoids chemical use but employs similar rinsing practices. Microbiological analysis of 100 samples (49 unprocessed and 51 MPVs) revealed no significant differences in microbial group counts (Enterobacteriaceae, coliforms, and E. coli) between the in natura (unprocessed) and MPV products. However, the prevalence of E. coli was higher in natura vegetables than in MPVs. The results indicated the presence of Salmonella DNA (from either dead or live cells or residual DNA) in 4 samples (3 in natura and 1 MPV) using conventional PCR, suggesting the presence of the pathogen in these samples. Listeria monocytogenes was absent, but Listeria innocua was found in two unprocessed products. The study suggests that certain MPVs have microbial loads similar to unprocessed vegetables, potentially serving as carriers for pathogen transmission. These findings emphasize the importance of understanding practices in Brazilian MPV processing plants, informing the implementation of control measures to improve MPV safety and shelf-life, thus ensuring microbiological safety.

Unveiling Fresh-Cut Lettuce Processing in Argentine Industries: Evaluating Salmonella Levels Using Predictive Microbiology Models

A survey was performed to gather information on the processing steps, conditions, and practices employed by industries processing ready-to-eat (RTE) leafy vegetables in Argentina. A total of seven industries participated in the survey. A cluster analysis of the data obtained was performed to identify homogeneous groups among the participating industries. The data collected were used as inputs of two predictive microbiology models to estimate Salmonella concentrations after chlorine washing, during storage and distribution of final products, and to rank the different practices according to the final estimated Salmonella levels. Six different clusters were identified by evaluating the parameters, methods, and controls applied in each processing step, evidencing a great variability among industries. The disinfectant agent applied by all participating industries was sodium hypochlorite, though concentrations and application times differed among industries from 50 to 200 ppm for 30 to 110 s. Simulations using predictive models indicated that the reductions in Salmonella in RTE leafy vegetables would vary in the range of 1.70-2.95 log CFU/g during chlorine-washing depending on chlorine concentrations applied, washing times, and vegetable cutting size, which varied from 9 to 16 cm2 among industries. Moreover, Salmonella would be able to grow in RTE leafy vegetables during storage and distribution, achieving levels of up to 2 log CFU/g, considering the storage and transportation temperatures and times reported by the industries, which vary from 4 to 14 °C and from 18 to 30 h. These results could be used to prioritize risk-based sampling programs by Food Official Control or determine more adequate process parameters to mitigate Salmonella in RTE leafy vegetables. Additionally, the information gathered in this study is useful for microbiological risk assessments.

Minimally Processed Vegetables in Brazil: An Overview of Marketing, Processing, and Microbiological Aspects

The global demand for minimally processed vegetables (MPVs) has grown, driven by changes in the population's lifestyle. MPVs are fresh vegetables that undergo several processing steps, resulting in ready-to-eat products, providing convenience for consumers and food companies. Among the processing steps, washing-disinfection plays an important role in reducing the microbial load and eliminating pathogens that may be present. However, poor hygiene practices can jeopardize the microbiological quality and safety of these products, thereby posing potential risks to consumer health. This study provides an overview of minimally processed vegetables (MPVs), with a specific focus on the Brazilian market. It includes information on the pricing of fresh vegetables and MPVs, as well as an examination of the various processing steps involved, and the microbiological aspects associated with MPVs. Data on the occurrence of hygiene indicators and pathogenic microorganisms in these products are presented. The focus of most studies has been on the detection of Escherichia coli, Salmonella spp., and Listeria monocytogenes, with prevalence rates ranging from 0.7% to 100%, 0.6% to 26.7%, and 0.2% to 33.3%, respectively. Foodborne outbreaks associated with the consumption of fresh vegetables in Brazil between 2000 and 2021 were also addressed. Although there is no information about whether these vegetables were consumed as fresh vegetables or MPVs, these data highlight the need for control measures to guarantee products with quality and safety to consumers.

Microbial and Parasitic Contamination of Vegetables in Developing Countries and Their Food Safety Guidelines

The safety of humans is of paramount importance in the vegetable production chain. Evidence of microbial and parasitic contamination of these products poses a great threat to consumers. This is an emerging issue the world is battling, and it is still in the process of unravelling. However, one of the contributing factors responsible for the rapid spread of these pathogens to millions of people among other factors is the distribution of food in our food systems. The purpose of this study was to draw the attention of producers, retailers, consumers, and various stakeholders to the occurrence and potential hazard of these organisms, their contamination origin, and food safety protocols. Among the food system, vegetables play a major role, and their consumption has increased as they form a larger portion of daily diets. This urge for healthy diets coupled with changing dietary habits and human population explosion has therefore accelerated their production. This has resulted in parasitic and microbial contamination gaining grounds in salad vegetables, and as such, a wide range of microbes such as Escherichia coli O157: H7, Listeria monocytogenes, Salmonella spp., Shigella, and Staphylococcus, and parasites such as Giardia lamblia, Entamoeba coli, Entamoeba histolytica, Cystoisospora belli, Toxoplasma gondii, Trichuris trichiura, and Ascaris lumbricoides have been isolated from them. Therefore, major routes for salad vegetable contamination and prevention methods have been pointed out in this review article. The topic of protective countermeasures will also be covered here in this review. Notwithstanding, several control measures have been reported to be effective and efficient in removing or eliminating pathogens, including treatment of irrigation water and fertilizers, use of disinfectants like vinegar and saltwater, irradiation, ozone, and bacteriophages. Though consumption of vegetables and salads is encouraged due to their nutritional advantage, appropriate systems should be put in place to ensure their safety.

Salmonella enterica in soybean production chain: Occurrence, characterization, and survival during soybean storage

This study aimed to determine Salmonella enterica occurrence along the soybean meal production chain (raw material, in-processing samples, final products, and in the environment of five processing plants), characterize the isolates, and assess the survival of Salmonella Senftenberg 775W in soybeans stored under different temperature conditions. Among 713 samples analyzed, 12.9% (n = 92) were positive for Salmonella enterica. Dust collected inside and outside processing plants (n = 148) comprised the samples with the highest positivity for Salmonella enterica, 47.3%. The occurrence of Salmonella enterica varied among the different processing plants. Twenty-nine (n = 29) Salmonella serotypes were isolated, with S. Mbandaka as the most frequent serotype, whereas S. Typhimurium was mainly linked to final product samples (soybean meal). S. Senftenberg 775W did not survive for a long time in soybean stored at 20-37 °C, but at 20 °C, cells were viable for more than 60 days. This study suggests that soybean meal may harbor Salmonella serotypes related to foodborne disease outbreaks in humans and can be responsible for Salmonella introduction into livestock and, consequently, in foods of animal origin. This study provides crucial data on contamination pathways of Salmonella in the soybean production chain, contributing to the understanding of Salmonella epidemiology which is strategic for the development of preventive and control measures to reduce the burden of salmonellosis linked to products of animal origin.

Effect of a direct-fed microbial (10-G Armor) on feedlot performance, carcass characteristics, and prevalence of Salmonella in fed-beef heifers

Crossbred beef heifers [N = 1,394; initial shrunk body weight (BW) 291 ± 9.9 kg] were used to investigate the efficacy of 10-G Armor (Life Products, Inc., Norfolk, NE; 10-G) upon feedlot performance, carcass characteristics, and fecal and subiliac lymph nodes Salmonella prevalence. Heifers were blocked by day of arrival and allocated to 1 of 20 pens (N = 70 heifers/pen) and assigned one of two treatments (10 pens/treatment) : no direct fed microbial (CON) or 2g/heifer/d of L. acidophilus, E. faecium, P. pentosaceus, L. brevis and L. plantarum respectively (Life Products, Inc., Norfolk, NE; 10-G). Twenty four animals were randomly selected from each pen for Salmonella sampling. Recto-anal mucosal swab samples (RAMS) were obtained at initial processing and harvest; subiliac lymph nodes were collected at harvest. In addition, pen surface fecal pats were collected and composited by pen (10 pats per composite, 5 composites per pen) on day 0, 52, 120 and 192. Data were analyzed as a generalized complete block design and pen served as the experimental unit. No differences were observed in live growth performance metrics (P ≥ 0.55). Yield grade distributions did not differ between treatments (P ≥ 0.62), however cattle fed 10-G tended (P = 0.06; 14.6 vs 18.9%) to have fewer USDA Select carcasses and more (P = 0.09; 73.6 vs 78.0%) USDA Choice carcasses. Cattle fed 10-G tended (P = 0.10; 9.2% vs 12.3%) to have fewer liver abscesses and had fewer (P = 0.04; 5.3 vs 8.5%) severe liver abscesses. Salmonella prevalence of RAMS did not differ between treatments at initial processing (P = 0.97; CON = 11.6%, 10-G = 11.5%) or at harvest (P = 0.91; CON = 99.0%, 10-G = 98.6%), however RAMS differed (P < 0.01) in Salmonella prevalence between the two collection times. Cattle fed 10-G had a lower frequency of Salmonella positive lymph nodes (P = 0.01; CON = 15.8%, 10-G = 7.4%) than CON. However, Salmonella log (mpn/g) of lymph nodes did not differ between treatments at harvest (P = 0.34; CON = 0.73, 10-G = 0.34). These data indicate that cattle fed 10-G have decreased rates of severe liver abscesses without altering live animal performance or carcass characteristics. Supplementation of 10-G significantly reduced prevalence rate of Salmonella recovered from the subiliac lymph nodes. The factors responsible for the observed difference in the effects of 10-G on Salmonella warrants further investigation

African nightshades (Solanum nigrum complex): The potential contribution to human nutrition and livelihoods in sub-Saharan Africa

Achieving zero hunger in sub-Saharan Africa (SSA) without minimizing postharvest losses of agricultural products is impossible. Therefore, a holistic approach is vital to end hunger, simultaneously improving food security, diversity, and livelihoods. This review focuses on the African nightshades (ANS) Solanum spp. contribution to improving food and nutrition security in SSA. Different parts of ANS are utilized as food and medicine; however, pests and diseases hinder ANS utilization. African nightshade is rich in micronutrients such as β-carotene, vitamins C and E, minerals (iron, calcium, and zinc), and dietary fiber. The leaves contain a high amount of nutrients than the berries. Proper utilization of ANS can contribute to ending hidden hunger, mainly in children and pregnant women. Literature shows that ANS contains antinutritional factors such as oxalate, phytate, nitrate, and alkaloids; however, their quantities are low to cause potential health effects. Several improved varieties with high yields, rich in nutrients, and low alkaloids have been developed in SSA. Various processing and preservation techniques such as cooking, drying, and fermentation are feasible techniques for value addition on ANS in SSA; moreover, most societies are yet to adopt them effectively. Furthermore, promoting value addition and commercialization of ANS is of importance and can create more jobs. Therefore, this review provides an overview of ANS production and challenges that hinder their utilization, possible solutions, and future research suggestions. This review concludes that ANS is an essential nutritious leafy vegetable for improving nutrition and livelihoods in SSA.

Systematic Review and Meta-analysis: Salmonella spp. prevalence in vegetables and fruits

In this study, a systematic review and a meta-analysis were conducted to analyse recent worldwide information about the prevalence of Salmonella spp. in vegetables and fruits to estimate the effect of the different processes such as washing, cutting or disinfection, and place of sampling. A systematic search was conducted for articles from 2014 to 2020 published to date regarding prevalence of Salmonella spp. in vegetables and fruits, without excluding material by location, or author. It was possible to determine eight categories for vegetables and fruits in comparison with the meta-analysis which showed five categories due to data availability. Results showed prevalence for Salmonella spp. of 0.1%, 0.2%, 13.7%, 0.1%, and 0% for fruits, leafy vegetables, mixed vegetables related to ready-to-eat salads (RTE), tubercles, and tomatoes, respectively. Moreover, categories such as fruits, tubercles, and tomatoes as associated with different types of preparations and places of sampling (Retail stores, fresh products wholesale, street markets, distribution centers, farms, and processing plants) did not present a significant combined effect on the prevalence of Salmonella spp. Likewise, leafy, and mixed vegetables showed differences associated with a type of processing, where leafy fresh unprocessed vegetables had a significant positive effect on the prevalence of the pathogen regarding the RTE products. These findings may be useful for the construction of a quantitative model of risk assessment as a means to characterize the differences among the sort of vegetable, fruit, type of processing, and place of sampling.

Microbiological quality and safety of minimally processed parsley (Petroselinum crispum) sold in food markets, southeastern Brazil

AIMS

This study evaluated the microbiological quality and safety of minimally processed parsley sold in southeastern Brazilian food markets.

METHODS AND RESULTS

One hundred samples were submitted to the enumeration of Enterobacteriaceae by plating on MacConkey agar. Colonies of Enterobacteriaceae were randomly selected and identified by MALDI-TOF MS. Samples were also tested for Listeria monocytogenes and Salmonella sp. The mean count of Enterobacteriaceae was 6·0 ± 1·0 log CFU per gram, while 18 genera (including 30 species) of bacteria belonging to this family were identified. Salmonella and L. monocytogenes were not detected, while L. innocua was found in two samples and L. fleischmannii was found in one sample. Moreover generic Escherichia coli was found in three samples, all from different brands of minimally processed parsley.

CONCLUSIONS

Even though microbial pathogens were not isolated, a variety of indicator micro-organisms were identified, including vegetable spoilers and species capable of causing human opportunistic infections. These results suggest hygienic failures and/or lack of temperature control during processing and storage of these ready-to-eat products.

SIGNIFICANCE AND IMPACT OF STUDY

This study highlights the need for control measures during the production chain of minimally processed parsley in order to reduce microbial contamination and the risks of foodborne diseases.

Predictive Growth Modeling of Listeria monocytogenes in Rice Balls and Its Risk Assessment

This study aimed to investigate the growth of Listeria monocytogenes in rice balls and to conduct its microbial risk assessment based on the Korean dietary pattern. Each tuna or ham rice ball was mixed with mayonnaise, soy sauce, or gochujang, a Korean traditional fermented red peeper paste, which was artificially contaminated with L. monocytogenes and then stored at 7°C–25°C to assess bacterial growth. Growth data were analyzed using three primary models (the Huang, Baranyi, and Gompertz models), and the growth pattern was found to fit well to the Baranyi model based on the following five statistical criteria: root mean square error (0.38–0.56), Akaike’s information criterion (−51.55–−26.99), coefficient of determination (0.72–0.97), bias factor (0.97–1.01), and accuracy factor (1.06–1.18). The effects of temperature on bacterial growth rate and lag time were evaluated using the square root model. The minimum growth temperature for L. monocytogenes in tuna or ham rice balls was the lowest when they were mixed with mayonnaise (−9.44°C or −15.37°C, respectively). Risk assessment using FDA-iRISK showed that tuna or ham rice balls mixed with gochujang exhibited the highest microbial risk among all the rice balls tested, regardless of the storage temperature. Tuna or ham rice balls mixed with gochujang had the highest disability-adjusted life years per year (0.015) followed by ham rice balls mixed with soy sauce (0.011–0.015) or mayonnaise (0.006–0.015) and then tuna rice balls mixed with soy sauce (0.006–0.008) or mayonnaise (<0.001). In conclusion, our results, determined using predictive growth models, allow the assessment of potential risk ranking associated with the consumption of rice balls contaminated with L. monocytogenes based on the number of illnesses experienced per serving and the disease burden.

Modelling the combined effect of chlorine, benzyl isothiocyanate, exposure time and cut size on the reduction of Salmonella in fresh-cut lettuce during washing process

This work aimed to study the effect of the combination of Sodium hypochlorite, the most used disinfectant by the vegetable industry, with a natural antimicrobial, benzyl-isothiocyanate (BITC), considering cutting surface and contact time, on the reduction of Salmonella in fresh-cut produce in washing operations under typical industrial conditions. Overall, the combinations of disinfectant and process parameters resulted in a mean reduction of Salmonella of 2.5 log CFU/g. According to statistical analysis, free chlorine and BITC concentrations, contact time and cut size exerted a significant effect on the Salmonella reduction (p ≤ 0.05). The optimum combination of process parameter values yielding the highest Salmonella reduction was a lettuce cut size of 15 cm2 washed for 110 s in industrial water containing 160 mg/L free chlorine and 40 mg/L BITC. A predictive model was also derived, which, as illustrated, could be applied to optimize industrial disinfection and develop probabilistic Exposure Assessments considering the effect of washing process parameters on the levels of Salmonella contamination in leafy green products. The present study demonstrated the efficacy of chlorine to reduce Salmonella populations in fresh-cut lettuce while highlighting the importance of controlling the washing process parameters, such as, contact time, cut size and concentration of the disinfectant to increase disinfectant efficacy and improve food safety.

Microbial Contamination of Organically and Conventionally Produced Fresh Vegetable Salads and Herbs from Retail Markets in Southwest Germany

A total of 189 samples of fresh products (leafy salads, ready-to-eat mixed salads, and fresh herbs) bought in retail in Southwest Germany were investigated for their microbiological quality and the presence of pathogenic bacteria, including Salmonella spp., Listeria monocytogenes, and presumptive Bacillus cereus. Total aerobic mesophilic plate counts (TAC) ranged from 5.5 to 9.6 log colony-forming units (CFUs) per gram. Enterobacteria and pseudomonads were the predominant microorganisms and were detected in all samples with counts between 5.0 and 9.2 log CFU/g. Strains of Escherichia coli were detected in 9 salad (7.9%) and 25 herb samples (33.3%). Significant differences in bacterial counts were found between conventionally and organically-grown products: in herbs the counts of moulds were significantly higher in organically-grown products, while E. coli was only detected in conventionally-grown products. In conventionally-grown salad samples, yeast counts were significantly higher. Salmonella Enteritidis was only detected in two conventionally- and in one organically-produced salad samples (2.6%). No coagulase-positive staphylococci were detected in fresh salads as well as in herbs. High levels of B. cereus sensu lato (≥3 log CFU/g) were detected in 19 vegetable salads (16.7%) and even in 55 samples of fresh herbs (73.3%). Listeria monocytogenes could not be detected in fresh herbs; however, three L. monocytogenes strains were isolated from two conventionally-produced salad samples and belonged to PCR serogroup IIa. Although our results indicate a high microbial load in fresh salads and herbs in Southwest Germany in 2015, the incidences of human pathogenic bacteria, that is, L. monocytogenes, Salmonella spp., and coagulase-positive staphylococci strains, were low.

High microbial loads found in minimally-processed sliced mushrooms from Italian market

There is an increased consumer interest in minimally processed vegetables that has led to the development of products, such as pre-cut sliced mushrooms. Few data are available on the hygienic condition and the presence of foodborne pathogens in such products. Therefore, the current study aimed to evaluate the safety and hygienic characteristics of both ready-to-eat and ready-to-cook, pre-cut sliced mushrooms obtained from a local Italian market. For the evaluation of the hygienic condition, the aerobic mesophilic bacteria, aerobic psychrotrophic bacteria and Escherichia coli enumerations were performed. Salmonella spp., Listeria monocytogenes and Campylobacter spp. were considered in the assessment of the foodborne pathogens. High microbial loads were detected, including counts higher than 5 log CFU/g for E. coli and 6 log CFU/g for the other bacteria counts considered, but no pathogens were found. Ready-to-eat and ready-to-cook products differed only for aerobic mesophilic counts (7.87 and 8.26 log CFU/g, respectively, P=0.003). Strategies to enhance the hygienic level of the mushrooms, particularly the ready-to-eat products, are needed.

Frequency of Enteroparasites and Bacteria in the Leafy Vegetables Sold in Brazilian Public Wholesale Markets

The consumption of raw vegetables is related to health benefits. However, these foods might be source of foodborne diseases. The objective of the present study was to perform a microbiological and parasitological evaluation of the leafy vegetables commercially sold in five regions of Brazil at public wholesale markets. The 12 types of leafy vegetables (144 samples) were curly lettuce, looseleaf lettuce, red lettuce, chives, coriander, kale, basil, arugula, parsley, iceberg lettuce, chicory, and bean sprouts. The prevalences of total coliforms (88 to 100%) and thermotolerant coliforms (37 to 100%) were high, but Salmonella was not detected in any of the analyzed samples. All open markets sold vegetables contaminated with enteroparasites, mainly Entamoeba sp., Balantidium coli, Strongyloides sp., Ascaris sp., Enterobius vermicularis, and Ancylostomidae. Contamination was detected in all the regions (north, northeast, central west, southeast, and south) and types of vegetables, with higher prevalences in the northeast region, mainly in basil, lettuce, and chives. Contamination of vegetables by potentially pathogenic microorganisms is a national problem, and the distribution centers should improve quality control of these commercial vegetables. Considering the high frequency of enteroparasites and bacteria and the potential risk of disease transmitted by vegetables, we suggest greater enforcement of the sanitary surveillance of food offered to the public.

Simultaneous and individual quantitative estimation of Salmonella, Shigella and Listeria monocytogenes on inoculated Roma tomatoes (Lycopersicon esculentum var. Pyriforme) and Serrano peppers (Capsicum annuum) using an MPN technique

Simultaneous and individual enumeration of Salmonella, Shigella and Listeria monocytogenes was compared on inoculated Roma tomatoes and Serrano peppers using an Most Probable Number (MPN) technique. Samples consisting of tomatoes (4 units) or peppers (8 units) were individually inoculated with a cocktail of three strains of Salmonella, Shigella or L. monocytogenes, or by simultaneous inoculation of three strains of each pathogen, at low (1.2-1.7 log CFU/sample) and high (2.2-2.7 log CFU/sample) inocula. Samples were analyzed by an MPN technique using universal pre-enrichment (UP) broth at 35 °C for 24 ± 2 h. The UP tubes from each MPN series were transferred to enrichment and plating media following adequate conventional methods for isolating each pathogen. Data were analyzed using multifactorial analysis of variance (p < 0.05) and LSD multiple rang test. There were differences (p < 0.05) in recovery of simultaneous and individual bacteria inoculated (individual > simultaneous), type of bacteria (Salmonella > Shigella and L. monocytogenes), type of sample (UP broth > pepper and tomato), and inoculum level (high > low). The MPN technique was effective for Salmonella on both commodities. Shigella counts were higher on tomatoes compared to peppers, (p < 0.05), and for L. monocytogenes on peppers (p < 0.05).

Microbiological Quality of Organic and Conventional Leafy Vegetables

The aim of this study was to assess the microbiological profile of leafy vegetables from organic and conventional farming (n=70). The microbiological parameters analyzed consisted of aerobic mesophilic bacteria, yeasts and molds, coliforms at 30 and 45°C, and Salmonella ssp. A biochemical identification of the Enterobacteriaceae species was carried out. Some Enterobacteriaceae species were identified in the produce from both farming systems and Hafnia alvei was the most widespread specie observed. Salmonella spp. was not detected in the samples analyzed. The microbial counts for indicator microorganisms were, in general, higher for conventional leaves when compared to those produced by organic farming.

Microbiological and Sensory Quality of Fresh Ready-to-Eat Artichoke Hearts Packaged under Modified Atmosphere

In recent years the sales of minimally processed vegetables have grown exponentially as a result of changes in consumer habits. The availability of artichoke buds as a ready-to-eat product would be, therefore, highly advantageous. However, minimally processed artichoke hearts are difficult to preserve because of their rapid browning and the proliferation of naturally occurring microorganisms. We developed artichoke hearts prepared as ready-to-eat products that maintain the characteristics of the fresh product. The microbiological stability, sensory qualities, and shelf life of the processed artichoke hearts were determined. During the shelf life, Salmonella, Listeria monocytogenes, and Escherichia coli counts were below the limits legally established by European regulations for minimally processed vegetables. The pH played an important role in microbial growth. Artichoke hearts had lower microbial counts in experiments conducted at pH 4.1 than in experiments conducted at pH 4.4, although the recommended threshold value for total plate count (7 log CFU/g) was not exceeded in either case. Sensory parameters were affected by the microorganisms, and artichoke products at lower pH had better sensory qualities. Vacuum impregnation techniques, modified atmosphere packaging, and low storage temperature were very effective for increasing the shelf life of minimally processed artichokes. The average shelf life was approximately 12 to 15 days.

Microbiology of organic and conventionally grown fresh produce

Fresh produce is a generalized term for a group of farm-produced crops, including fruits and vegetables. Organic agriculture has been on the rise and attracting the attention of the food production sector, since it uses eco-agricultural principles that are ostensibly environmentally-friendly and provides products potentially free from the residues of agrochemicals. Organic farming practices such as the use of animal manure can however increase the risk of contamination by enteric pathogenic microorganisms and may consequently pose health risks. A number of scientific studies conducted in different countries have compared the microbiological quality of produce samples from organic and conventional production and results are contradictory. While some have reported greater microbial counts in fresh produce from organic production, other studies do not. This manuscript provides a brief review of the current knowledge and summarizes data on the occurrence of pathogenic microorganisms in vegetables from organic production.

Assessing the effect of sodium dichloroisocyanurate concentration on transfer of Salmonella enterica serotype Typhimurium in wash water for production of minimally processed iceberg lettuce (Lactuca sativa L.)

This study evaluated the impact of sodium dichloroisocyanurate (5, 10, 20, 30, 40, 50 and 250 mg l(-1) ) in wash water on transfer of Salmonella Typhimurium from contaminated lettuce to wash water and then to other noncontaminated lettuces washed sequentially in the same water. Experiments were designed mimicking the conditions commonly seen in minimally processed vegetable (MPV) processing plants in Brazil. The scenarios were as follows: (1) Washing one inoculated lettuce portion in nonchlorinated water, followed by washing 10 noninoculated portions sequentially. (2) Washing one inoculated lettuce portion in chlorinated water followed by washing five noninoculated portions sequentially. (3) Washing five inoculated lettuce portions in chlorinated water sequentially, followed by washing five noninoculated portions sequentially. (4) Washing five noninoculated lettuce portions in chlorinated water sequentially, followed by washing five inoculated portions sequentially and then by washing five noninoculated portions sequentially in the same water. Salm. Typhimurium transfer from inoculated lettuce to wash water and further dissemination to noninoculated lettuces occurred when nonchlorinated water was used (scenario 1). When chlorinated water was used (scenarios 2, 3 and 4), no measurable Salm. Typhimurium transfer occurred if the sanitizer was ≥10 mg l(-1) . Use of sanitizers in correct concentrations is important to minimize the risk of microbial transfer during MPV washing.

SIGNIFICANCE AND IMPACT OF THE STUDY

In this study, the impact of sodium dichloroisocyanurate in the wash water on transfer of Salmonella Typhimurium from inoculated lettuce to wash water and then to other noninoculated lettuces washed sequentially in the same water was evaluated. The use of chlorinated water, at concentration above 10 mg l(-1) , effectively prevented Salm. Typhimurium transfer under several different washing scenarios. Conversely, when nonchlorinated water was used, Salm. Typhimurium transfer occurred in up to at least 10 noninoculated batches of lettuce washed sequentially in the same water.

Assessing the growth of Escherichia coli O157:H7 and Salmonella in spinach, lettuce, parsley and chard extracts at different storage temperatures

AIMS

The objective of this work was to study the growth potential of Escherichia coli O157:H7 and Salmonella spp. in leafy vegetable extracts at different temperature conditions.

METHODS AND RESULTS

Cocktails of five strains of E. coli O157:H7 and of Salmonella enterica were used. Inoculated aqueous vegetable extracts were incubated at 8, 10, 16 and 20°C during 21 days. Microbial growth was monitored using Bioscreen C(®) . In spinach extract, results showed that for E. coli O157:H7 and Salmonella significant differences (P < 0·05) for μabs (maximum absorbance rate) were obtained. For both pathogens, growth in chard was slightly lower. In contrast, iceberg lettuce and parsley showed the lowest values of μabs , below 0·008 h(-1) . The coefficients of variance (CoV) calculated for the different replicates evidenced that at low temperature (8°C) a more variable behaviour of both pathogens is expected (CoV > 180%).

CONCLUSIONS

This study provides evidence that aqueous extracts from vegetable tissues can result in distinct growth niche producing different response in various types of vegetables.

SIGNIFICANCE AND IMPACT OF THE STUDY

Finally, these results can be used as basis to establish risk rankings of pathogens and leafy vegetable matrices with relation to their potential growth.

Assessment of the microbiological quality of fresh produce on sale in Sicily, Italy: preliminary results

Background

Fresh produce occupies an increasingly important place in the human food supply because of its health-promoting nutritional properties. Most fresh produce is eaten raw or after minimal processing and, consequently, pathogen contamination can represent a serious health risk. There has been an increase in foodborne outbreaks and cases associated with fresh produce, but literature data about the prevalence of pathogen contamination are inconsistent. This study was undertaken to assess the hygienic quality and the prevalence of the most common bacterial pathogens in fresh produce sold in retail markets in Sicily. A total of 125 samples of different types of vegetables were examined by standardized microbiological methods.

Results

The aerobic mesophilic count ranged between 2 log and 7 log cfu g⁻¹ and the Enterobacteriaceae counts between < 1 log and 6 log cfu g⁻¹, with statistically significant differences between unprocessed and minimally processed products (p < 0.05). Escherichia coli was detected only in leaf vegetables at a concentration of 2 log - 3 log cfu g⁻¹. Enterococci were found at a concentration of 2 log - 4 log cfu g⁻¹. Coagulase positive Staphylococci and sulphite-reducing Clostridia were not detected in any sample. Three samples tested positive for Listeria monocytogenes, Yersinia enterocolitica and Salmonella veneziana.

Conclusion

Our study provides updated data on the microbiological quality of retail vegetables and confirms the need to implement strategies to increase microbial safety of fresh produce.

Microbiological quality and safety assessment of lettuce production in Brazil

The microbiological quality and safety of lettuce during primary production in Brazil were determined by enumeration of hygiene indicators Escherichia coli, coliforms and enterococci and detection of enteric pathogens Salmonella and E. coli O157:H7 in organic fertilizers, soil, irrigation water, lettuce crops, harvest boxes and worker's hands taken from six different lettuce farms throughout the crop growth cycle. Generic E. coli was a suitable indicator for the presence of Salmonella and E. coli O157:H7, while coliforms and enterococci were not. Few pathogens were detected: 5 salmonellae and 2 E. coli O157:H7 from 260 samples, of which only one was lettuce and the others were manure, soil and water. Most (5/7) pathogens were isolated from the same farm and all were from organic production. Statistical analysis revealed the following environmental and agro-technical risk factors for increased microbial load and pathogen prevalence in lettuce production: high temperature, flooding of lettuce fields, application of contaminated organic fertilizer, irrigation with water of inferior quality and large distances between the field and toilets. Control of the composting process of organic fertilizers and the irrigation water quality appear most crucial to improve and/or maintain the microbiological quality and safety during the primary production of lettuce.

Growth potential of Salmonella and Listeria monocytogenes in ready-to-eat lettuce and collard greens packaged under modified atmosphere and in perforated film

This study was aimed at determining the effects of different storage scenarios on the growth potential of Salmonella strains and Listeria monocytogenes in ready-to-eat (RTE) mixes of iceberg and crisp lettuces (Lactuca sativa) and collard greens (Brassica oleracea). Vegetables were submitted to minimal processing, experimentally contaminated to achieve 10(1) and 10(2) CFU/g, packed under modified atmosphere and in perforated film, and submitted to the following storage scenarios: I = 100 % of the shelf life (6 days) at 7°C; II = 70 % of shelf life at 7°C and 30 % at 15°C; III = 30 % at 7°C and 70 % at 15°C; IV = 100 % at 15°C. Higher populations of Salmonella were observed in lettuce mixes than in collard greens; the opposite occurred with L. monocytogenes. Keeping the RTE vegetables at 15°C during the whole shelf life (scenario IV) or part of it (scenarios II and III) markedly influenced the growth of both pathogens in most of the scenarios studied (P < 0.05). Growth potentials of strains of Salmonella and L. monocytogenes were significantly different depending on the scenarios in samples packed with perforated film in comparison to those stored under modified atmosphere (P < 0.05). The findings indicate that even contamination as low as 10(1) CFU/g can lead to high populations if there is temperature abuse during storage (15°C). This study of the behavior of Salmonella and L. monocytogenes in RTE vegetables provides insights that may be useful in the development of strategies to control pathogen growth in these products.

Modeling the growth rate and lag time of different strains of Salmonella enterica and Listeria monocytogenes in ready-to-eat lettuce

The growth parameters (growth rate, μ and lag time, λ) of three different strains each of Salmonella enterica and Listeria monocytogenes in minimally processed lettuce (MPL) and their changes as a function of temperature were modeled. MPL were packed under modified atmosphere (5% O₂, 15% CO₂ and 80% N₂), stored at 7-30 °C and samples collected at different time intervals were enumerated for S. enterica and L. monocytogenes. Growth curves and equations describing the relationship between μ and λ as a function of temperature were constructed using the DMFit Excel add-in and through linear regression, respectively. The predicted growth parameters for the pathogens observed in this study were compared to ComBase, Pathogen modeling program (PMP) and data from the literature. High R² values (0.97 and 0.93) were observed for average growth curves of different strains of pathogens grown on MPL. Secondary models of μ and λ for both pathogens followed a linear trend with high R² values (>0.90). Root mean square error (RMSE) showed that the models obtained are accurate and suitable for modeling the growth of S. enterica and L. monocytogenes in MP lettuce. The current study provides growth models for these foodborne pathogens that can be used in microbial risk assessment.

Growth potential of Salmonella spp. and Listeria monocytogenes in nine types of ready-to-eat vegetables stored at variable temperature conditions during shelf-life

Growth potential (δ) is defined as the difference between the population of a microorganism at the end of shelf-life of specific food and its initial population. The determination of δ of Salmonella and Listeria monocytogenes in RTE vegetables can be very useful to determine likely threats to food safety. However, little is known on the behavior of these microorganisms in several RTE vegetables. Therefore, the aim of this study was to determine the δ of both pathogens in nine different types of RTE vegetables (escarole, collard green, spinach, watercress, arugula, grated carrot, green salad, and mix for yakisoba) stored at refrigeration (7°C) and abuse temperature (15°C). The population of aerobic microorganisms and lactic acid bacteria, including those showing antimicrobial activity has been also determined. Results indicated that L. monocytogenes was able to grow (δ≥0.5 log(10)) in more storage conditions and vegetables than Salmonella. Both microorganisms were inhibited in carrots, although a more pronounced effect has been observed against L. monocytogenes. The highest δ values were obtained when the RTE vegetables were stored 15°C/6days in collard greens (δ=3.3) and arugula (δ=3.2) (L. monocytogenes) and arugula (δ=4.1) and escarole (δ=2.8) (Salmonella). In most vegetables and storage conditions studied, the counts of total aerobic microorganisms raised significantly independent of the temperature of storage (p<0.05). Counts of lactic acid bacteria were higher in vegetables partially or fully stored at abuse temperature with recovery of isolates showing antimicrobial activity. In conclusion, the results of this study show that Salmonella and L. monocytogenes may grow and reach high populations in RTE vegetables depending on storage conditions and the definition of effective intervention strategies are needed to control their growth in these products.