Mixed Salad Research Articles

Effect of Nitrogen Supply and Storage Temperature on Vitamin C in Two Species of Baby Leaf Rocket, and the Potential of These Crops for a Nutrient Claim in Australia

Baby leaf crops such as rocket are popular in mixed salads and add flavor and diversity to these dishes. Rocket leaves contain many beneficial compounds to human health, including vitamin C. It is important to determine abiotic factors that influence the concentration of this compound; in order to improve the supply of quality produce with a high nutritional value. The possibility of a nutrient claim for leaves of perennial wall rocket [Diplotaxis tenuifolia (L.) DC.] and annual garden rocket (Eruca sativa Mill.) was examined under the Food Standards Australia New Zealand (FSANZ) framework. Crops were supplied with 0, 100, 200, and 300 kg · ha−1 of nitrogen (N); leaves were stored at 0, 4, and 7°C for 15 days. The cultivar and amount of nitrogen supplied to perennial wall rocket did not affect the concentration of vitamin C in leaves at harvest, with a mean of 79.6 mg 100 g−1. For annual garden rocket there was an interaction between cultivar and nitrogen supply, with higher levels of supply generally resulting in lower vitamin C concentrations at harvest. The postharvest stability of vitamin C in both crops was best maintained at the lowest storage temperature. The results of this study illustrate that if stored at 0°C, both species contain vitamin C in sufficient quantities 15 days after harvest, to result in a “good source” health claim [>25% recommended daily intake (RDI)]. However, the storage temperature in the supply chain is typically ∼7°C, still permitting a “source” health claim (>10% RDI) for both species.

First Report of Necrotic Leaf Spot Caused by Plectosphaerella cucumerina on Lamb's Lettuce in Southern Italy

During spring 2013, lamb's lettuce plants (Valerianella locusta) cv. Calarasi (Rijk Zwaan) in a commercial greenhouse in Sele Valley (Salerno Province, southern Italy) exhibited small, black-brown, irregular spots (1 mm2) that became necrotic, enlarged, and coalesced. The spots were mostly on the tips of leaves, and were surrounded by a yellow halo. The disease was severe under greenhouse conditions of 60 to 90% RH and maximum air temperature of 26°C, and affected up to 70% of the plants. The greenhouses covered an area of ~3,000 ha where many salad species are grown. Tissue fragments were excised from symptomatic leaves, sterilized by sequential dipping in 70% ethanol for 30 s and in 1% NaOCl for 30 s, rinsed in sterilized distilled water, and placed in 9-cm-diameter petri dishes containing potato dextrose agar (PDA) medium amended with streptomycin sulfate (0.1 g/liter). The plates were incubated at 24°C in the dark. A fungus was isolated consistently from infected leaf tissue after 4 days. Each colony was whitish to orange. Mycelium was hyaline, branched, septate, 3 to 4 μm wide, with numerous anastomosis-forming hyphal coils. Conidiophores were solitary, hyaline, smooth, thin-walled, unbranched or rarely irregularly branched. Conidiogenous cells were phialidic, determinate, discrete, smooth, solitary, and formed on hyphal coils. Phialides were aseptate or occasionally 1-septate near the base. Conidia (n = 100) were ellipsoidal, hyaline, smooth, septate or aseptate, and 6.6 ± 0.9 × 2.8 ± 0.4 μm. On the basis of morphological criteria (3), the fungus was ascribed to Plectosphaerella cucumerina (L.) Laterr. (anamorph Plectosporium tabacinum). An aliquot (50 ng) of genomic DNA extracted from mycelium of five cultures obtained by monosporic isolation on PDA was used as template for a PCR reaction with primers ITS5/ITS4, specific for the ITS 5.8S rDNA region of fungi (3). The 500-bp sequences amplified from the five isolates were identical, and the sequence of isolate Val-2 was submitted to GenBank (KF753234). Sequence analysis with BLASTn showed 100% identity of this sequence to the ITS-5.8S rDNA sequences of 11 isolates of P. cucumerina in GenBank. Three isolates were selected for pathogenicity tests on the lamb's lettuce cv. Calarasi. Before planting, seeds were surface-disinfected in 1% NaOCl and rinsed with sterilized distilled water. Plants (35 days old, 30 plants tested/isolate) were grown in 0.7-liter pots filled with a sterilized (autoclaved at 112°C for 1 h on each of two consecutive days) mixture of soil:sand:perlite (2:1:1), and inoculated by spraying the leaves with a spore suspension (106 CFU/ml, ~3 ml applied/plant) of each isolate prepared from 7-day-old cultures on PDA. As a control, five plants were sprayed with sterilized water. All plants were incubated in a growth chamber at 90% RH with a 12-h photoperiod at 24°C. Leaf spots typical of those on the original symptomatic plants appeared 7 to 10 days after inoculation on all inoculated plants. No symptoms were observed on control plants. P. cucumerina was re-isolated only from symptomatic leaves, as described for the original isolations. P. cucumerina has been associated with root and collar roots of some horticultural crops (1), and a leaf spot on Diplotaxis tenuifolia (2), often grown in rotation with lamb's lettuce in southern Italy. To our knowledge, this is the first report of P. cucumerina as a pathogen of V. locusta in Italy or elsewhere. The disease caused economic loss to lamb's lettuce, primarily used in Italy in fresh-cut, mixed salads.

Occurrence of Fusarium Wilt Caused by Fusarium oxysporum f. sp. spinaciae on Spinach (Spinacia oleracea) in Southern Italy.

Fusarium oxysporum f. sp. spinaciae (Sherb.) W.C. Snyder & H.N. Hansen is the causal agent of Fusarium wilt of spinach (Spinacia oleracea L.), a serious disease of spinach worldwide (1). In September 2011, several plants of an unknown spinach variety grown for the production of packaged ready-to-eat salads (4th range) in a greenhouse in southern Italy (Pontecagnano, Salerno) showed yellowing of older leaves, reduced root development, blackening of the vascular tissues, and wilting of 60-day-old plants; necrotic lesions at the taproot base were occasionally present. Yield losses up to 70% were observed. Small portions of symptomatic tissues from the basal vascular stem were disinfected with sodium hypochlorite (1% active Cl2), rinsed with sterile water, and then placed on potato dextrose agar (PDA) amended with neomycin (50 ppm), chloramphenicol (50 ppm), and streptomycin (100 ppm). Pink to white colonies with a fluffy aerial mycelium rapidly developed; pale orange sporodochia containing thin walled macroconidia, mostly 3-septate, short to medium length, with a curved apical cell and a notched or foot-shaped basal cell were present. Oval to reniform, 0-septate microconidia were formed on typical single short monophyalides or abundantly on false heads. Chlamydospores were formed singly or in pairs in 1-month-old plates. On the basis of these morphological characters, the fungus was identified as F. oxysporum. In order to confirm the diagnosis, DNA from a single spore culture of an isolate (11-113PANT3) was extracted, amplified by PCR using primers EF 1H and EF 2T (2) corresponding to a segment of the transcription elongation factor 1α (EF-1α) gene, and the PCR product sequenced at GenChron (Rome, Italy). A homology search in GenBank using the BLASTn algorithm showed 100% identity of the obtained sequence with several sequences of formae speciales of F. oxysporum, including the NRRL26871, corresponding to F. oxysporum f. sp. spinaciae. For the pathogenicity tests, 15-day-old spinach seedlings of the variety Spargo F1 were inoculated at the cotyledon stage by dipping the roots for 5 min in a monosporic conidial suspension of the isolate 11-113PANT3 at a concentration of 1 × 106 CFU ml-1. Twenty plantlets in two replicates were inoculated and incubated in a growth chamber at 26°C. The same number of uninoculated plants were used as controls. Yellowing of leaves and vascular blackening was observed in all inoculated plants that wilted and died within 10 days. The colonies re-isolated from all the inoculated plants were identified morphologically as F. oxysporum, thus fulfilling Koch's postulates. Experiments were repeated twice. Based on host source and sequence similarity, the fungus was identified as F. oxysporum f. sp. spinaciae. To our knowledge, this is the first report of this species on spinach in Italy. Since this first report, Fusarium wilting of spinach has been frequently observed in other greenhouses, and it is becoming of concern for Italian salad mix producers. Continuous cropping and high-input cultivation systems are among the possible factors favoring the spread of the fungus. The management of the disease could be achieved through the adoption of crop rotation, the use of partially resistant cultivars, and by spinach seed treatments.

Modelling of transpiration rate of grape tomatoes. Semi-empirical and analytical approach

Transpiration is a well known physiological process of water loss from fresh products, associated with visual and texture degradation and loss of market value. A loss of 3–5% of the initial mass may cause in fresh products loss of freshness and visual attractiveness. Grape tomato has been increasingly accepted by consumers as “snacking tomato” and as an ingredient in mixed salads of fresh-cut vegetables. An experimental procedure was developed to record the associated with transpiration, water loss in grape tomatoes (Solanum lycopersicum, Lobello F1), at temperatures 10, 15 and 20 °C and relative humidity 70, 80 and 92%. Water activity was calculated and correlated with the respective mass loss; its average value was found 0.988 ± 0.01. The mean transpiration rates ranged between 0.012 and 0.058 mg cm−2 h−1 for water vapour pressure deficit range of 0.061–0.662 kPa. A semi-empirical and an analytical model were developed to correlate the mass loss of grape tomatoes with the storage conditions (temperature and relative humidity) and storage time. Both provided satisfactory fit to the experimental data. Finally, the air-film mass transfer coefficient (ka) and skin mass transfer coefficient (ks) were calculated and the ks coefficient correlated efficiently with an exponential equation with the respective water vapour pressure deficit.

Occurrence of pathogenic Escherichia coli in commercially available fresh vegetable products in Korea

Pathogenic E. coli is a major foodborne pathogen associated with gastroenteritis worldwide. Fresh vegetable products as well as raw meat and meat products have been recognized as important modes of transmission within the foodborne route. The objective of the present study was to determine the presence of six virulence factors (stx 1, stx 2, lt, st, eaeA, and ial) in E. coli isolated from fresh vegetable products to provide information on risk assessment of pathogenic E. coli in Korea. From 416 collected samples, including vegetable salad mix, sprouts, baby leaf vegetables, and unpasteurized fruit and vegetable juices commercially available in Korea, a total of 30 samples were positive for E. coli strains, resulting in an overall prevalence of 7.2%. Of the 120 E. coli isolates, only one isolate (0.8%), which was obtained from unpasteurized fruit and vegetable juices, was confirmed to possess the eaeA gene, but lacked stx genes. This study showed that some fresh vegetable product samples were contaminated with enteropathogenic E. coli.

Prevalence and Concentration of Bacterial Pathogens in Raw Produce and Minimally Processed Packaged Salads Produced in and for The Netherlands

Recent outbreaks with vegetable or fruits as vehicles have raised interest in the characterization of the public health risk due to microbial contamination of these commodities. Because qualitative and quantitative data regarding prevalence and concentration of various microbes are lacking, we conducted a survey to estimate the prevalence and contamination level of raw produce and the resulting minimally processed packaged salads as sold in The Netherlands. A dedicated sampling plan accounted for the amount of processed produce in relation to the amount of products, laboratory capacity, and seasonal influences. Over 1,800 samples of produce and over 1,900 samples of ready-to-eat mixed salads were investigated for Salmonella enterica serovars, Campylobacter spp., Escherichia coli O157, and Listeria monocytogenes. The overall prevalence in raw produce varied between 0.11% for E. coli O157 and L. monocytogenes and 0.38% for Salmonella. Prevalence point estimates for specific produce/pathogen combinations ranged for Salmonella from 0.53% in iceberg lettuce to 5.1% in cucumber. For Campylobacter, this ranged from 0.83% in endive to 2.7% in oak tree lettuce. These data will be used to determine the public health risk posed by the consumption of ready-to-eat mixed salads in The Netherlands.

Microbiological Risk from Minimally Processed Packaged Salads in the Dutch Food Chain

The objective of this study was to evaluate the microbial hazard associated with the consumption of mixed salads produced under standard conditions. The presence of Salmonella, Campylobacter spp., and Escherichia coli O157 in the Dutch production chain of mixed salads was determined. Microbial prevalence and concentration data from a microbiological surveillance study were used as inputs for the quantitative microbial risk assessment. Chain logistics, production figures, and consumption patterns were combined with the survey data for the risk assessment chain approach. The results of the sample analysis were used to track events from contamination through human illness. Wide 95% confidence intervals around the mean were found for estimated annual numbers of illnesses resulting from the consumption of mixed salads contaminated with Salmonella Typhimurium DT104 (0 to 10,300 cases), Campylobacter spp. (0 to 92,000 cases), or E. coli (0 to 800 cases). The main sources of uncertainty are the lack of decontamination data (i.e., produce washing during processing) and an appropriate dose-response relationship.

An exploratory study of sensory attributes and consumer traits underlying liking for and perceptions of freshness for ready to eat mixed salad leaves in Italy

The role of sensory attributes and storage time information in driving liking for and perceptions of freshness for ready to eat vegetables was investigated in mixed salad leaves for different storage times (0, 3, 7 and 9days). A modified Repertory Grid Method was used to identify ten attributes describing consumer's perception of sensory properties over storage. Eighty-one consumers rated the overall liking, the intensity of sensory attributes and the level of freshness in salad samples at different storage times. Freshness was evaluated in blind and informed conditions. Furthermore, consumers filled in a Food Choice Questionnaire and rated the importance of six attributes known to be important for ready to eat salad choice. The relationships between sensory properties significantly affected by storage time, perceived freshness and liking showed that both liking and freshness were positively related to appearance attributes (green colour, salad assortment and leaf turgidity). The perceived level of freshness, expiry date and appearance were confirmed as the most important attributes for ready to eat salad choice. Two clusters of consumers (Cl1: n=49; Cl2: n=32) were identified based on the mean liking rating. The positive effects on health and mood as well as ethical concerns drove food choice more in Cl1 than in Cl2 subjects. No significant effect of storage time was found on liking ratings expressed by Cl1 in blind conditions, while a significant decrease of perceived freshness was observed. On the other hand, results from Cl2 in blind conditions showed a significant decrease of both liking and perceived freshness. Information about storage time significantly affected freshness ratings in Cl1 but did not influence those from Cl2.Results suggest that collection of sensory data, affective responses and information about the background of subjects is needed to fully investigate the perceptions of freshness from a consumer perspective.

Cyclosporiasis Outbreaks Traced to Salad Mix and Cilantro in Salsa

Cyclosporiasis Outbreaks Traced to Salad Mix and Cilantro in Salsa

A fast, reliable, and sensitive method for detection and quantification of Listeria monocytogenes and Escherichia coli O157:H7 in ready-to-eat fresh-cut products by MPN-qPCR.

In the present work we developed a MPN quantitative real-time PCR (MPN-qPCR) method for a fast and reliable detection and quantification of Listeria monocytogenes and Escherichia coli O157:H7 in minimally processed vegetables. In order to validate the proposed technique, the results were compared with conventional MPN followed by phenotypic and biochemical assays methods. When L. monocytogenes and E. coli O157:H7 were artificially inoculated in fresh-cut vegetables, a concentration as low as 1 CFU g−1 could be detected in 48 hours for both pathogens. qPCR alone allowed a limit of detection of 101 CFU g−1 after 2 hours of enrichment for L. monocytogenes and E. coli O157:H7. Since minimally processed ready-to-eat vegetables are characterized by very short shelf life, our method can potentially address the consistent reduction of time for microbial analysis, allowing a better management of quality control. Moreover, the occurrences of both pathogenic bacteria in mixed salad samples and fresh-cut melons were monitored in two production plants from the receipt of the raw materials to the early stages of shelf life. No sample was found to be contaminated by L. monocytogenes. One sample of raw mixed salad was found positive to an H7 enterohemorrhagic serotype.

Barriers to Trace-back in a Salad-associated EHEC Outbreak, Sweden, June 2013.

In June-July 2013, six counties notified the Swedish Institute for Communicable Disease Control of enterohaemorrhagic E.coli (EHEC) infections among attendees at a hotel in Dalarna, Sweden. An outbreak control team investigated to identify the source and implement control measures. We included individuals who attended the hotel between June 19th-25th in a cohort. We asked them about animal contact, swimming, and consumption of food items during this time using a questionnaire. A confirmed case was an EHEC O157:H7 outbreak strain positive individual who developed abdominal pain or diarrhoea between June 20th-July 2nd. We described the outbreak in time, place and person, calculated risk ratios (RR) and 95% confidence intervals (CI). We investigated the kitchen, tested and traced back implicated food items. 172 individuals responded. We identified 19 confirmed cases (Median age: 17 years, 64% female) with symptom onset between June 22nd-27th. Eating green salad on June 20th was associated with illness (RR:3.7;CI:1.3–11). The kitchen mixed green salads without records and destroyed leftovers immediately. Hence we could not conduct trace-back or obtain microbiological confirmation. Green salad contaminated before entering the kitchen was the likely outbreak source. We recommended early collaboration with food agencies and better restaurant records to facilitate future investigations.

Infectious disease surveillance update

As of Aug 1, 2013, the US Centers for Disease Control and Prevention (CDC) have been notified of 400 cases of the intestinal infection Cyclosporiasis across 16 states. At least 22 patients have been admitted to hospital in five states. Salad mix produced by a farm in Mexico has been associated with the outbreak in Iowa and Nebraska. Cyclosporiasis is acquired by ingestion of food or drink contaminated with the parasite Cyclospora cayetanensis. Symptoms usually develop within 1 week and include diarrhoea, nausea, and fever. The US Food and Drug Administration, CDC, and public health officials have collaborated in the ongoing national investigation.

An innovative and low-cost gapless traceability system of fresh vegetable products using RF technologies and EPCglobal standard

Traceability requirements in supply chain management are getting more and more strict in order to ensure product quality and public safety. Such requirements are particularly difficult to reach in the agro-food sector, especially for fresh ready-to-eat (RTE) vegetables, where specific needs exist; for example, mixed RTE salads are made of different produces, and there is the need to track and trace the treatments all the ingredients separately receive, avoiding gaps in the electronic histories. Traceability global standards, along with the adoption of Radio Frequency (RF) technologies have been widely experimented in this field; nevertheless, there are still many difficulties. Wireless Sensor Networks (WSN) cause a big impact on the existing information system, and meet the opposition of professionals in the field such as agronomists who feel out of the process. Additionally, Ultra-High Frequency (UHF) Radio Frequency IDentification (RFID)-based item-level traceability is still too expensive.In this paper, we propose an integrated and innovative solution for the “gapless” traceability of fresh RTE vegetables produced by an Italian agro-food company. Most approaches to sensor-based implementations completely replace agronomists. By contrast, our solution keeps the agronomists in the greenhouses but empowers them with smart technology. The Agronomist Android mobile App uses Near Field Communication (NFC) technology to allow the linking of plants and traceability information, following the EPCglobal standard. We achieve low costs by using DataMatrix technology for item-level tagging, while restricting the use of UHF RFID to coarse-grained grouping levels (case and pallet). We adopt the Enterprise Service Bus (ESB) architectural style for granting flexibility and scalability while preserving compatibility with legacy applications. We obtained the experimental results we report by using a Living Laboratory approach; the experiments we carried on have demonstrated the good performances of RFID tags and readers when used in conjunction with fresh vegetables products, as well as the actual effectiveness of the proposed gapless traceability system.

Campylobacterinfection associated with consumption of duck liver pâté: a retrospective cohort study in the setting of near universal exposure

A retrospective cohort study was performed following several reported cases of gastrointestinal illness after a catered event. The attack rate was 45/77 (58·4%) by clinical case definition, with four individuals confirmed to have Campylobacter. There was near universal exposure to most foodstuffs served; consumption of duck liver pâté [relative risk (RR) 2·53, 95% confidence interval (CI) 1·05-6·10], mixed leaf salad (RR 2·91, 95% CI 1·22-6·92) and table water (RR undefined, P < 0·01) were associated with illness in univariate analysis, with only the latter associated in the final multivariable model (P < 0·001). Samples of cooked duck liver pâté subsequently prepared using identical methods at the venue were contaminated with Campylobacter jejuni and C. coli; water sampling was negative. Making inferences about causation in the presence of near universal exposures in this study required consideration of the limitations of statistical analysis, with the most compelling evidence of the causal role of inadequately prepared duck liver pâté provided by environmental investigation.

Nondestructive and Continuous Monitoring of Oxygen Levels in Modified Atmosphere Packaged Ready‐to‐Eat Mixed Salad Products Using Optical Oxygen Sensors, and Its Effects on Sensory and Microbiological Counts during Storage

The objective of this study was to determine the percentage oxygen consumption of fresh, respiring ready-to-eat (RTE) mixed leaf salad products (Iceberg salad leaf, Caesar salad leaf, and Italian salad leaf). These were held under different modified atmosphere packaging (MAP) conditions (5% O2 , 5% CO2 , 90% N2 (MAPC-commercial control), 21% O2 , 5% CO2 , 74% N2 (MAP 1), 45% O2 , 5% CO2 , 50% N2 (MAP 2), and 60% O2 , 5% CO2 , 35% N2 (MAP 3)) and 4 °C for up to 10 d. The quality and shelf-life stability of all packaged salad products were evaluated using sensory, physiochemical, and microbial assessment. Oxygen levels in all MAP packs were measured on each day of analysis using optical oxygen sensors allowing for nondestructive assessment of packs. Analysis showed that with the exception of control packs, oxygen levels for all MAP treatments decreased by approximately 10% after 7 d of storage. Oxygen levels in control packs were depleted after 7 d of storage. This appears to have had no detrimental effect on either the sensory quality or shelf-life stability of any of the salad products investigated. Additionally, the presence of higher levels of oxygen in modified atmosphere packs did not significantly improve product quality or shelf-life stability; however, these additional levels of oxygen were freely available to fresh respiring produce if required. This study shows that the application of optical sensors in MAP packs was successful in nondestructively monitoring oxygen level, or changes in oxygen level, during refrigerated storage of RTE salad products.

Assessment and Use of Optical Oxygen Sensors as Tools to Assist in Optimal Product Component Selection for the Development of Packs of Ready-to-Eat Mixed Salads and for the Non-Destructive Monitoring of in-Pack Oxygen Levels Using Chilled Storage.

Optical oxygen sensors were used to ascertain the level of oxygen consumed by individual salad leaves for optimised packaging of ready-to-eat (RTE) Italian salad mixes during refrigerated storage. Seven commonly found leaves in Italian salad mixes were individually assessed for oxygen utilisation in packs. Each leaf showed varying levels of respiration throughout storage. Using the information obtained, an experimental salad mix was formulated (termed Mix 3) which consisted of the four slowest respiring salad leaves—Escarole, Frisee, Red Batavia, Lollo Rosso. Mix 3 was then compared against two commercially available Italian salads; Mix 1 (Escarole, Frisee, Radicchio, Lollo Rosso) and Mix 2 (Cos, Frisee, Radicchio, Lollo Rosso). Optical sensors were used to non-destructively monitor oxygen usage in all mixes throughout storage. In addition to oxygen consumption, all three salad mixes were quality assessed in terms of microbial load and sensorial acceptability. In conclusion, Mix 3 was found to consume the least amount of oxygen over time, had the lowest microbial load and was most sensorially preferred (p < 0.05) in terms of overall appearance and acceptability. This study clearly shows the potential that oxygen sensors possess in terms of assisting in the optimised development of commercial RTE salad products.

Yersinia enterocoliticaOutbreak Associated with Ready-to-Eat Salad Mix, Norway, 2011

In 2011, an outbreak of illness caused by Yersinia enterocolitica O:9 in Norway was linked to ready-to-eat salad mix, an unusual vehicle for this pathogen. The outbreak illustrates the need to characterize isolates of this organism, and reinforces the need for international traceback mechanisms for fresh produce.

Listeria monocytogenes prevalence and serotype diversity in various foods

The aim of the current study was to estimate the prevalence and serotype diversity of Listeria monocytogenes in various foods of Estonian origin such as meat, milk, fish, pastry, crop, culinary, fruit and vegetable with special reference to ready-to-eat (RTE) foods. In 2008–2010, a total of 554 (2.6%) of 21,574 food samples were positive for L. monocytogenes in Estonia. L. monocytogenes contamination was significantly (P < 0.001) higher in raw meat and raw meat products (18.7%), raw mixed salads (18.5%) and in raw milk (18.1%) compare to raw fish products (8.8%). Among RTE fish products, cold-smoked fish products were most frequently contaminated with L. monocytogenes (32.9%). Generally, the counts of L. monocytogenes in tested products remained under 10 colony forming units (CFU) per gram of product. Only 2.9% and 0.8% of the RTE fish products contained L. monocytogenes in range of 100–1000 CFU/g and >1000 CFU/g at the end of shelf life. The majority of tested isolates (73.6%) belonged to serotype 1/2a, followed by 1/2b (7.4%), 1/2c (7.4%), 4b (7.7%) and 4d (3.5%). Our findings showed that the prevalence of L. monocytogenes in various RTE food categories, in spite of higher prevalence among raw products, was generally low in Estonia.

Microbial safety of raw mixed-vegetable salad sold as an accompaniment to street vended cooked rice in Accra, Ghana

A survey of 90 randomly selected subjects indicated raw mixed-vegetable salad as a popular accompaniment to cooked rice sold by street-food vendors in the Kokomlemle municipality of Accra, Ghana, but the salad was generally considered unwholesome and a potential cause of diarrhoea. A survey of 15 vendors of cooked rice indicated that the sources of raw vegetables, method of transportation from the sources to the kitchens, and methods of storing the raw vegetables before processing, as well as the methods of processing and sale, made the raw mixed-vegetable salad accompaniment a potential source of food poisoning from microbial contamination. Microbial analysis of samples of the salads obtained from five randomly selected vendors in the mornings and afternoons, over 15 days, indicated that bacterial counts for all samples exceeded the recommended World Health Organization (WHO) standard of Log10 3.0 cfu/g. Levels of Pseudomonas, Salmonella typhi, Shigella sp., and Streptococcus faecalis did not show any significant difference (P<0.05) among vendors and did not differ significantly (P<0.05) over the 15 days. Significantly, higher levels of microbial contamination (P<0.05) occurred in the afternoon, than in the morning samples. The results confirm that the raw mixed vegetable salads which are sold as accompaniment to street vended cooked rice in the Kokomlemle municipality contain S. faecalis from fecal contamination, Pseudomonas, Shigella sp., and S. typhi which could cause gastrointestinal infections and the highest risk was from the afternoon samples.

High throughput quality and safety assessment of packaged green produce using two optical oxygen sensor based systems

Two new analytical techniques, the GreenLight™ system for rapid enumeration of total viable counts (TVC) in food homogenates and the Optech™ system for non-destructive sensing of residual O2 in package headspace were applied to examine a total of 206 packages of green produce with the aim to assess their main quality and safety characteristics. Three types of ready-to-eat salads—Iceberg lettuce, Caesar salad & Italian leaf mix salad—packed under different modified atmosphere (5% CO2, 5–60% O2) and stored at 4 °C for up to 10 days were examined by monitoring their TVC and headspace O2, CO2. The new detection methodology was compared with traditional methods showing good correlation with Dansensor gas analyzer for O2 (R2 = 0.9912) and with agar plating ISO4833:2003 method for TVC (R2 = 0.7749). The lowest TVC was achieved in 5% oxygen packed salad while in the other conditions showed no clear improvement. Both systems provide affordable high speed, sample throughput and proved themselves to be useful, convenient and capable of supplying important information about the key physical and biological parameters of individual packs.