Research – Ultrasonic cleaning of salad could reduce instances of food poisoning

Science Daily

A new study has shown that gentle streams of water carrying sound and microscopic air bubbles can clean bacteria from salad leaves more effectively than current washing methods used by suppliers and consumers. As well as reducing food poisoning, the findings could reduce food waste and have implications for the growing threat of anti-microbial resistance.

Salad and leafy green vegetables may be contaminated with harmful bacteria during growing, harvesting, preparation and retail leading to outbreaks of food poisoning which may be fatal in vulnerable groups.

Because there is no cooking process to reduce the microbial load in fresh salads, washing is vital by the supplier and the consumer.

Washing with soap, detergent bleach or other disinfectants is not recommended and the crevices in the leaf surface means washing with plain water may leave an infectious dose on the leaf. Even if chemicals are used, they may not penetrate the crevices.

In this new study, published in the journal Ultrasound in Medicine and Biology, scientists used acoustic water streams to clean spinach leaves directly sourced from the field crop, then compared the results with leaves rinsed in plain water at the same velocity.

Professor Timothy Leighton of the University of Southampton, who invented the technology and led this research, explains: “Our streams of water carry microscopic bubbles and acoustic waves down to the leaf. There the sound field sets up echoes at the surface of the leaves, and within the leaf crevices, that attract the bubbles towards the leaf and into the crevices. The sound field also causes the walls of the bubbles to ripple very quickly, turning each bubble into a microscopic ‘scrubbing’ machine. The rippling bubble wall causes strong currents to move in the water around the bubble, and sweep the microbes off the leaf. The bacteria, biofilms, and the bubbles themselves, are then rinsed off the leaf, leaving it clean and free of residues.”

The results showed that the microbial load on samples cleaned with the acoustic streams for two minutes was significantly lower six days after cleaning than on those treated without the added sound and bubbles. The acoustic cleaning also caused no further damage to the leaves and demonstrated the potential to extend food shelf life, which has important economic and sustainability implications.

Improving how food providers clean fresh produce could have a major role to play in combating the threat of anti-microbial resistance. In 2018 and 2019, there were fatal outbreaks of different strains of E. coli on romaine lettuce in the USA and Canada and samples from humans infected showed strains that are resistant to antibiotics.

University of Southampton PhD student Weng Yee (Beverly) Chong, who was part of the research team added: “I am very grateful to Vitacress and EPSRC for funding my PhD. I came from an engineering background, and took Professor Leighton’s classes, but he told me that I could be a trans-disciplinary PhD student, and become a microbiologist whilst increasingmy engineering skills. I am also very grateful to Sloan Water Technology Ltd.: They opened up their laboratories for use by students like me, so that I can keep working on my experiments. It is an exciting environment to work in because they are doing so much inventive work to combat the pandemic and infections as a whole.”

Previously as part of her PhD Beverly has studied how the technology could reduce the infection risk to horses and other livestock through hay cleaning.

The work was sponsored by Vitacress, whose Group Technical Director Helen Brierley said: “Ensuring food safety for our products is an essential requirement. At Vitacress, we wash our produce in natural spring water, and this type of ground-breaking new technology helps to enhance our process whilst ensuring our commitment to protect the environment is maintained. We are always interested in new developments and are excited to see the results of this research.”

Story Source:

Materials provided by University of SouthamptonNote: Content may be edited for style and length.

Journal Reference:

  1. Weng Yee Chong, Thomas J. Secker, Craig N. Dolder, Charles W. Keevil, Timothy G. Leighton. The Possibilities of Using Ultrasonically Activated Streams to Reduce the Risk of Foodborne Infection from SaladUltrasound in Medicine & Biology, 2021; DOI: 10.1016/j.ultrasmedbio.2021.01.026

Research – Prevalence of Listeria species on food contact surfaces in Washington State apple packinghouses


The 2014 caramel apple listeriosis outbreak was traced back to cross-contamination between food contact surfaces (FCS) of equipment used for packing and fresh apples. For Washington State, the leading apple producer in the U.S with 79% of its total production directed to the fresh market, managing the risk of apple contamination with Listeria monocytogenes within the packing environment is crucial. The objectives of this study were to determine the prevalence of Listeria spp. on FCS in Washington State apple packinghouses over two packing seasons, and to identify those FCS types with the greatest likelihood to harbor Listeria spp. Five commercial apple packinghouses were visited quarterly over two consecutive year-long packing seasons. A range of 27 to 50 FCS were swabbed at each facility to detect Listeria spp. at two timings of sampling, (i) post-sanitation and (ii) in-process (three hours of packinghouse operation), following a modified protocol of the FDA’s Bacteriological Analytical Manual method. Among 2,988 samples tested, 4.6% (n=136) were positive for Listeria spp. Wax coating was the unit operation from which Listeria spp. were most frequently isolated. The FCS that showed the greatest prevalence of Listeria spp. were polishing brushes, stainless steel dividers and brushes under fans/blowers, and dryer rollers. The prevalence of Listeria spp. on FCS increased throughout apple storage time. The results of this study will aid apple packers in controlling for contamination and harborage of L. monocytogenes and improving cleaning and sanitation practices of the most Listeria-prevalent FCS.IMPORTANCE Since 2014, fresh apples have been linked to outbreaks and recalls associated with post-harvest cross-contamination with the foodborne pathogen L. monocytogenes These situations drive both public health burden and economic loss and underscore the need for continued scrutiny of packinghouse management to eliminate potential Listeria spp. niches. This research assesses the prevalence of Listeria spp. on FCS in apple packinghouses and identifies those FCS most likely to harbor Listeria spp. Such findings are essential for the apple packing industry striving to further understand and exhaustively mitigate the risk of contamination with L. monocytogenes to prevent future listeriosis outbreaks and recalls.

Research – Giardiasis Outbreaks — United States, 2012–2017


CDC Giardia2


What is already known about this topic?

Giardiasis is a diarrheal disease caused by the parasite Giardia duodenalis, the most common cause of intestinal parasite infections in the United States.

What is added by this report?

During 2012–2017, public health officials from 26 states reported 111 giardiasis outbreaks involving 760 cases. Leading causes of outbreaks were waterborne and person-to-person exposures. Private residences and child care facilities were the most common settings of giardiasis outbreaks across all transmission modes.

What are the implications for public health practice?

To prevent and control giardiasis outbreaks, CDC recommends prompt diagnosis, maintaining good hand hygiene, cleaning and disinfecting home environments and child care facilities, and monitoring water quality in private well

Giardiasis is a diarrheal disease caused by the parasite Giardia duodenalis, the most common cause of intestinal parasite infections in the United States. Transmission occurs when Giardia cysts spread from feces to water, food, surfaces, or skin and are then ingested. Illness is characterized by gastrointestinal symptoms, including diarrhea, abdominal cramps, greasy stools, bloating or gas, nausea, vomiting, weight loss, and dehydration. Approximately 50% of infections are asymptomatic (1,2). Most symptomatic Giardia infections are self-limited in duration; however, some persons might experience a reoccurrence of symptoms or develop long-term complications (3). During 2012–2017, public health officials from 26 states reported 111 giardiasis outbreaks (760 cases) to the National Outbreak Reporting System (NORS). Three main modes of transmission for these outbreaks were identified: water exposure in 29 (26%) outbreaks, person-to-person contact in 28 (25%) outbreaks, and contaminated food in six (5%) outbreaks. A single transmission mode could not be determined in 48 (43%) of the outbreaks. Private residences and child care facilities were the most common settings of outbreaks for all the transmission modes combined. To prevent and control giardiasis outbreaks, CDC recommends prompt diagnosis, maintaining good hand hygiene, cleaning and disinfecting home environments and child care facilities, and monitoring water quality in private wells.

A giardiasis outbreak is defined as the occurrence of two or more cases of illness epidemiologically linked to a common exposure (1). Health department officials from across the United States (state, local, and District of Columbia), U.S. territories,* and freely associated states voluntarily report outbreaks to NORS. This study included giardiasis outbreak reports submitted to NORS by December 30, 2019 and data reported during 2012–2017 (the year of the earliest case illness onset date through the most recent year for which data were available). NORS data summarized in this study include primary case counts, hospitalizations, and deaths; transmission mode; exposures and settings; and earliest onset date. Negative binomial regression analysis was conducted to assess for annual trends in outbreak counts using SAS (version 9.4; SAS Institute). This activity was reviewed by CDC and conducted consistent with applicable federal law and CDC policy.§

During 2012–2017, public health officials from 26 states reported 111 giardiasis outbreaks with 760 primary cases, 28 hospitalizations, 48 emergency department visits, and no deaths. Among the 703 cases with available data, 370 (53%) persons were male and 333 (47%) persons were female. Pennsylvania reported the largest number of outbreaks with 44 (40%), followed by Minnesota with 11 (10%); no other state reported >10 outbreaks (Figure 1). There was no significant trend in giardiasis outbreaks by year (χ2 = 0.67, p = 0.98) (Figure 2).

Among 29 (26%) waterborne outbreaks (370 cases), exposure sources included tap water systems (e.g., municipal systems or private wells) in nine outbreaks, outdoor freshwater consumption in seven outbreaks, treated recreational water in five outbreaks, untreated recreational water in four outbreaks, and “other” in four outbreaks (Table). Reported settings for waterborne outbreaks included 12 (41%) outdoor areas (e.g., parks and forests) five (17%) private residences, four (14%) camps or cabins, three (10%) community/municipality settings, three (10%) unknown, and two (7%) other settings. Person-to-person transmission was the primary mode identified in 28 (25%) outbreaks, resulting in 129 cases. The primary exposure settings for these outbreaks were 14 (50%) private residences and 12 (43%) child care facilities (Table). Among the 14 settings in private homes, nine (64%) were in households with children aged ≤5 years; two (14%) were in homes with only adults. Among the six (5%) foodborne outbreaks, all foods associated with the five known food exposures were eaten raw or with minimal or no processing. No outbreaks were attributed to animal contact or environmental contamination other than food and water (i.e., contact with objects or surfaces with Giardia). Among all 111 outbreaks, 48 (43%) had an indeterminate or unknown transmission mode, meaning that there was insufficient evidence to implicate one specific primary mode of transmission; 33 (69%) of these outbreaks occurred in private residences (Table).

Research – Growth of Listeria monocytogenes in Partially Cooked Battered Chicken Nuggets as a Function of Storage Temperature


Battered poultry products may be wrongly regarded and treated by consumers as ready-to-eat and, as such, be implicated in foodborne disease outbreaks. This study aimed at the quantitative description of the growth behavior of Listeria monocytogenes in fresh, partially cooked (non-ready-to-eat) battered chicken nuggets as function of temperature. Commercially prepared chicken breast nuggets were inoculated with L. monocytogenes and stored at different isothermal conditions (4, 8, 12, and 16 °C). The pathogen’s growth behavior was characterized via a two-step predictive modelling approach: estimation of growth kinetic parameters using a primary model, and description of the effect of temperature on the estimated maximum specific growth rate (μmax) using a secondary model. Model evaluation was undertaken using independent growth data under both constant and dynamic temperature conditions. According to the findings of this study, L. monocytogenes may proliferate in battered chicken nuggets in the course of their shelf life to levels potentially hazardous for susceptible population groups, even under well-controlled refrigerated storage conditions. Model evaluation demonstrated a satisfactory performance, where the estimated bias factor (Bf) was 0.92 and 1.08 under constant and dynamic temperature conditions, respectively, while the accuracy factor (Af) value was 1.08, in both cases. The collected data should be useful in model development and quantitative microbiological risk assessment in battered poultry products. View Full-Text

Germany – Safe Food: Protecting against foodborne infections in communal facilities


In its updated leaflet, the German Federal Institute for Risk Assessment (BfR) provides recommendations for the preparation of meals in communal facilities that regularly cater for particularly vulnerable groups of people.

Foodborne infections particularly endanger young children, pregnant women and very old or sick people. “Errors in the selection and preparation of food can have serious consequences for particularly vulnerable people and even lead to death,” says Professor Dr. Dr. Andreas Hensel, President of the German Federal Institute for Risk Assessment (BfR). “With the BfR leaflet “Safe Food”, we would like to support community facilities in serving safe food to these particularly sensitive groups of people as well.”

Link to the leaflet:

Foodborne illness can occur when pathogens enter commercial kitchens via raw ingredients or infected staff, are spread by hygiene failures in kitchens, and enter prepared foods. Temperature errors contribute to the survival and multiplication of pathogens in food.

Avoiding pathogens such as salmonella or listeria is particularly important when catering for sensitive individuals. Good hygiene and the right choice of ingredients and recipes reduce foodborne infections. Adequate food quality, proper storage and preparation of food, and staff training are also essential.

Fruit and vegetables should be washed thoroughly and peeled if possible. Low-acid fruit, vegetables and leafy salads must be eaten immediately after cutting or should be kept in the refrigerator until consumption. To protect against listeriosis, it may be advisable to reheat raw, but also already heated, ready-to-eat food before serving.

Most pathogens are killed when the food is heated to 72 degrees for at least two minutes in all parts during cooking. This requirement should be followed to prepare safe food.

While bacteria are killed when heated, bacterial spores can survive high temperatures. Such spores are able to germinate and the vegetative bacteria can multiply and form toxins. Keeping food hot until it is served at a minimum of 60 degrees on all parts of the heated food can prevent spores from germinating and bacteria from multiplying.

Establishments that regularly cater for particularly vulnerable persons have a special responsibility when selecting their staff. They should be competent, experienced and regularly trained.

USA – El Abuelito Listeria Pregnancy Related Illnesses Added to Outbreak Total

Food Poisoning Bulletin

Two El Abuelito Listeria pregnancy related illnesses were added to the listeriosis soft cheese outbreak total last week by the Centers for Disease Control and Prevention (CDC). That company’s queso fresco cheese was recalled earlier this month because lab tests conducted by the Connecticut Department of Health found the outbreak strain of Listeria monocytogenes in one sample of the product. Also last week, two more types of El Abuelito cheese were recalled: Quesillo (Oaxaca and string cheese) and Requeson (ricotta).

Ireland – Recall of Additional Batches of SFC Chicken Poppets Due to Presence of Salmonella


Category 1: For Action
Alert Notification: 2021.20 update 1
Product: The Original SFC Chicken Poppets, pack size:190g
Batch Code: Best before dates: 24.09.2021 and 31.10.2021
Country Of Origin: United Kingdom


Further to the FSAI’s food alert 2021.20SFC is recalling the above additional batches of its Chicken Poppets due to the detection of Salmonella. Batches with a best before date of 28.02.2022 were recalled previously. Point-of-sale recall notices will be displayed in Tesco stores.

Nature Of Danger:

People infected with Salmonella typically develop symptoms between 12 and 36 hours after infection, but this can range between 6 and 72 hours.  The most common symptom is diarrhoea, which can sometimes be bloody.  Other symptoms may include fever, headache and abdominal cramps.  The illness usually lasts 4 to 7 days. Diarrhoea can occasionally be severe enough to require hospital admission. The elderly, infants, and those with impaired immune systems are more likely to have a severe illness.

Action Required:


Consumers are advised not to eat the implicated batches.

SFC Chicken Poppets

Belgium – Basmati rice sachet (1kg) – Ochratoxin A – Basmati Rice


Recall of Carrefour
Product: Basmati rice sachet (1kg).
Problem: too high Ochratoxin A content in Basmati Rice.

Brussels, 04-03-2021 – Following a control and in order to guarantee the safety of the consumer, the SOUFFLET company asks to withdraw from the trade the “basmati rice” of the Carrefour brand (1kg) sold in the GROCERY department of certain Carrefour stores in Belgium. This product is also being recalled from consumers.

BASMATI RICE of the Carrefour brand
“Naturally flavored”
Conditioned by EMB 59606B
Product: Basmati rice sachet (1kg)
EAN: 3560070837984
Expiration date (DDM): 21/11/2022

Ochratoxin A is a mycotoxin produced by several microscopic fungi
(genera Penicillium and Aspergillus) and is naturally present in many
plant products around the world, such as cereals, coffee beans, cocoa and
dried fruits.

Only a large quantity of contaminated products can lead to health

All products have been withdrawn from sale. Some of these products were however marketed on the Belgian market before the withdrawal measure. It is therefore recommended that people who hold the products described above do not consume them and destroy them or return them to the point of sale where they will be reimbursed.

For any further information, you can contact the Carrefour Belgium consumer service by dialing the free number 0800.9.10.11 , from 8:30 am to 8:00 pm, Monday to Saturday.

The SOUFFLET company apologizes to Carrefour customers for the inconvenience caused.

France – Product recall: 200g tip of brie from Les Croisés brand – Listeria monocytogenes


Product recall: 200g tip of brie from Les Croisés brand


Risk of presence of Listeria monocytogenes


Those in possession of this product are asked not to consume it and to return it to the point of sale where it was purchased.

People who have consumed this product and who present with fever, isolated or accompanied by headaches, are invited to consult their attending physician, notifying him of this consumption.
Pregnant women should pay special attention to these symptoms, as well as immunocompromised people and the elderly. These symptoms may suggest listeriosis, a disease that can be serious and can take up to eight weeks to incubate.


▸ Barcode

▸ Packaging


▸ Health
stamp FR 88.115.001 CE

▸ Consumer service contact
0 800 86 52 86 Free service and call

▸ Source

Iceland – Salmonella in chicken pieces


Matvælastofnun warns against consuming SFC Boneless Bucket chicken bites due to salmonella contamination. Inputs that import the chicken pieces have recalled the product in consultation with the Reykjavík Health Inspectorate.

The FDA received information from the UK through the Infosan International Food Safety Authority and the Health Inspectorate had also received information from Resources.

The recall only applies to the following best for dates:

  • Product Name: SFC Boneless Bucket, Crunchy golden pieces of tasty, succulent Chicken Crispy Strips, Dippers and Poppets coated in a Southern Fried Style coating
  • Net amount: 650g
  • Barcode: 5031532020629
  • Storage conditions: Freezer, -18 ° C
  • Lot number: L19720
  • Best before date: 28-11-2021
  • Country of origin: Poland
  • Country of manufacture: United Kingdom
  • Importer: Aðföng, Skútuvogur 7-9, 104 Reykjavík
  • Distribution: Bargain shops all over the country

SFC chicken

Customers who have purchased the above product are asked not to consume it and discard it, but it can also be returned to the store where it was purchased for a refund. Further information can be obtained from Aðfang’s Quality Manager at tel. 530 5600 or via the email address gaedastjori at