listeria - The Future Of Food - safefood Knowledge Network2024-03-28T17:04:46Zhttps://safefoodkn.ning.com/food-safety-thought-leader-articles/feed/tag/listeriasafefood Sectoral Food Safety Review:Fresh Produce Sector (August 2021)https://safefoodkn.ning.com/food-safety-thought-leader-articles/safefood-sectoral-food-safety-review-fresh-produce-sector-august-2021-08-31T14:51:38.000Z2021-08-31T14:51:38.000Zsafefood Knowledge Network https://safefoodkn.ning.com/members/safefoodKnowledgeNetwork<div><p><strong><em>safe</em>food Sectoral Food Safety Review: Fresh Produce Sector</strong></p>
<p>When the risk of illness associated with a food product increases, the cause can often be traced back to an emerging consumer trend. Whether it’s people developing a taste for raw milk or a preference for undercooked burgers, foodie fads often run contrary to evidence-based public health advice.</p>
<p>Fresh produce provides another example. A trend for eating fruits and vegetables – including non-ready-to-eat frozen products – raw in formats such as smoothies and salads has been associated with an increase in outbreaks of foodborne illness. A <strong><em>safe</em>food</strong> conference in 2019 heard how consumer habits regarding consumption of fresh produce are changing. A lot of fresh produce is eaten raw, so no steps to reduce risks such as cooking the product have taken place.</p>
<p>A particular issue is the growth of <em>Listeria</em> on fresh leafy vegetables driven by increasing consumer demand for healthy, freshly prepared, convenient products that require a minimal amount of effort and time for preparation.<img class="align-right" src="{{#staticFileLink}}9507875098,RESIZE_710x{{/staticFileLink}}" alt="9507875098?profile=RESIZE_710x" width="710" /></p>
<p>Ireland’s retail market for fresh produce was valued at €1.2bn in 2019 of which 14.2% consisted of fresh-cut produce. In recent years there have been several examples where <em>Listeria</em> has been detected on such products. In 2019, batches of organic kale were recalled by Dunnes Stores and SuperValu due to the detection of <em>Listeria monocytogenes</em>. In 2018, meanwhile, the detection of <em>Listeria</em> <em>monocytogenes</em> in a batch of spinach leaves caused a range of fresh unwashed spinach products to be recalled from a number of retailers and caterers.</p>
<p><em>Listeria</em> is a relatively uncommon pathogen compared to <em>Salmonella</em>, <em>Escherichia coli</em> and <em>Campylobacter</em> but it is considerably more deadly. Listeriosis commonly requires hospitalisation and has a mortality rate estimated at 25-30%. Infants, the elderly, pregnant women and the immunocompromised are particularly vulnerable and therefore public health authorities view it as critically important that the risk is carefully managed and controlled in the production environment.</p>
<p>One of the most high-profile cases of recent years began in 2015 when an outbreak of <em>Listeria</em> caused by the bacteria <em>Listeria monocytogenes</em> impacted five EU countries – Austria, Denmark, Finland, Sweden and the UK – with 53 recorded cases and 10 deaths. The outbreak was linked by genome sequencing to frozen sweetcorn and possibly other vegetables produced from a single plant in Hungary.</p>
<p>Due to the long shelf life of frozen vegetable products and the long incubation period of listeriosis (on average 1-3 weeks but possibly up to 70 days) the risk to consumers remains for some time. The World Health Organisation (WHO) said the 2015 outbreak served as a reminder to consumers that frozen raw vegetables should be cooked or heat-treated properly before consumption (<em>Listeria</em> is relatively easy to destroy by cooking to temperatures above 70°C for 2 minutes or equivalent).<img class="align-center" src="{{#staticFileLink}}9507876671,RESIZE_710x{{/staticFileLink}}" alt="9507876671?profile=RESIZE_710x" width="710" /></p>
<p><strong>Sampling surge</strong></p>
<p>So how prevalent is <em>Listeria</em> in fresh produce now? Perhaps unsurprisingly, the number of samples of fruit and vegetables tested across the EU has increased significantly in recent years (+189% between 2017 and 2019), likely driven by awareness of that 2015 multi-country outbreak of <em>Listeria monocytogenes.</em> The latest EU Zoonoses report, based on 2019 data submitted by EU member states, provided data from investigations of <em>Listeria monocytogenes</em> on 2,357 units of ready-to-eat (RTE) fruit and vegetables tested. The overall occurrence was 1.7% (compared with 1.8% in 1,257 units tested in 2018). For RTE salads, 3,138 samples were analysed and 109 samples (3.5%) were found to be positive, while for spices and herbs, 291 samples were analysed and two samples (0.7%) were found positive.</p>
<p>As well as there being an onus on consumers to reduce the risk of contamination by preparing fresh produce properly before eating it, growers too have a responsibility. Anything which comes into contact with fresh produce has the potential to cause contamination. <em>Listeria</em> is widely present in the environment: soil is the primary transmission vector, but water too is a significant source of contamination of raw material along the farm to fork supply chain either directly via water used as an ingredient or indirectly via aerosols or condensation. And because it can survive and grow in chilled conditions, <em>Listeria</em> will also continue to grow in numbers in the food factory environment, such as in drains and free-standing water, unless good manufacturing and hygiene practices are applied. Moreover, the use of contaminated production lines for several food products may represent an additional risk for potential cross-contamination of the various final products produced at the plant.</p>
<p>Beyond the factory gate, there is also a risk of variance in labelling standards with some frozen vegetable products clearly stating that they are raw and require cooking, others implying the need to cook and others with next to no clarity. This puts the onus on consumers to apply their own understanding of safe usage.</p>
<p><strong>Risk management</strong></p>
<p>At the growing stage, businesses can take a number of steps to minimise the risk of contamination. FSAI advice is for growers to select a suitable site, for example by avoiding soils which are shallow, highly permeable or prone to flooding or run-off, and avoiding soils which naturally have high levels of contaminants which can accumulate in certain root and leafy crops.</p>
<p>Growers should also reduce the risk of contamination from animals by reducing access of livestock, wild animals, pests and pets, including to the source of water used to irrigate fresh produce.</p>
<p>Good harvesting practices should be followed at all times; training and suitable facilities should be provided for staff; and all growers must establish a traceability system that can effectively identify and remove unsafe food from the market in the event of a food safety incident occurring.</p>
<p>Down the supply chain in the processing environment, guidance produced by the British Frozen Food Federation (BFFF) into the management of risk of listeriosis from frozen vegetables states that the primary controls are based on the application of the HACCP principles and the controls applied will determine the microbiological quality of the product. Often these include criteria that can be measured on line such as temperature, time, pH and water activity as well as the application of good manufacturing and hygiene practices. Sampling and testing plans should also be used to verify that these controls are satisfactory to provide confidence that standards are being met for the finished product.</p>
<p>Current surveillance systems are not guaranteed to pick up <em>Listeria</em> contamination. Dr. Achim Schmalenberger, Senior Lecturer at the Department of Biological Sciences, School of Natural Sciences at the University of Limerick, says his group’s research shows that growth is not always detected by all testers, adding that more research is needed in order to find out why some studies find growth on a certain leafy vegetable, while others do not.</p>
<p>Dr. Schmalenberger and his colleague Paul Culliney published a recent paper on the growth potential of <em>Listeria monocytogenes</em> on spinach and rocket in which they found that many studies did not find growth of the same pathogen on spinach. In conclusion, Dr. Schmalenberger says there may be more unknown factors at play that determine when a pathogen like <em>Listeria</em> is going to grow on a leafy RTE vegetable.</p>
<p>From the point of view of producers trying to minimise the risks of contamination, Dr. Schmalenberger says there is not a single solution in place so the most prudent approach is a multiple hurdle approach starting with the producer and ending with the consumer.<img class="align-right" src="{{#staticFileLink}}9507877274,RESIZE_710x{{/staticFileLink}}" alt="9507877274?profile=RESIZE_710x" width="600" /></p>
<p><strong>Beyond <em>Listeria</em></strong></p>
<p>Outside of <em>Listeria</em>, other disease outbreaks concerning fruits and vegetables continue to require vigilance from producers, regulators and from consumers. In the US, a number of <em>E. coli</em> outbreaks since 2019 have been linked to produce including romaine lettuces, ready to eat salads and clover sprouts.</p>
<p>Within the EU, by far the most high-profile, and deadly, recent incidence occurred in Germany in 2011 when an outbreak of enterohemorrhagic <em>E. coli</em> (EHEC) sickened more than 4,000 people and killed 49. Initially, cucumbers originating in Spain were suspected to be the cause of the outbreak leading to import bans and destruction of products. However, it ultimately emerged that fenugreek seeds imported from Egypt were the most likely culprit.</p>
<p>An outbreak of <em>Salmonella</em> presumed to be linked to imported melons has more recently been the subject of an investigation by EFSA. Between 15 March and 6 July 2021, 348 confirmed S. Braenderup sequence type 22 (ST22) cases were reported in 12 European Union/European Economic Area countries and the United Kingdom. The cases were spread throughout the countries with a total of 68 cases requiring hospitalisation and no deaths reported. In its assessment, EFSA concluded that Galia melons from a batch imported from a Honduran producer were the probable vehicles of infection.</p>
<p>Specific to Ireland, a foodborne outbreak of cryptosporidiosis in 2020 has been linked to salad leaves. Forty cases were linked to the outbreak of which several cases shared a common restaurant history. Cross-referencing of food exposures identified a common salad box served in the implicated restaurants, sourced from a single farm, which lead to a precautionary product recall.</p>
<p><strong><em>Cyclospora</em> risk</strong></p>
<p> </p>
<p><em>Cryptosporidium</em> is notifiable in both the UK and Ireland, albeit a recently published article in the <em>Irish Medical Journal</em> on the 2020 salad leaves incident concluded that routine laboratory surveillance is not robust at Irish or European level and to accurately measure the incidence of <em>Cryptosporidium</em> infection in Europe, a comprehensive, uniform surveillance system is needed.</p>
<p>On the other hand <em>Cyclospora</em>, another protozoan parasite which can cause watery diarrhoea, anorexia, nausea, flatulence, fatigue, abdominal cramping, low-grade fever, and weight loss lasting for many weeks, is not notifiable. Presenting at the 2019 <strong><em>safe</em>food</strong> conference, Prof. Rachel Chalmers, director of the national <em>Cryptosporidium</em> Reference Unit for England and Wales in Swansea, explained that this means reporting is voluntary, surveillance may be incomplete, and cases might not be followed up.</p>
<p>Prof. Chalmers explained that cases of cyclosporiasis have most commonly been linked to overseas travel, in particular in South and Central America, South and South East Asia, the Middle East and Africa. Most recently, outbreaks were identified among holiday makers returning from Mexico. </p>
<p>Incidents tend to be linked to consumption of uncooked soft fruit especially berries, salad or vegetables, and fresh herbs (fresh mint in drinks is one specific example).</p>
<p>Although readily treatable with trimethoprim sulfamethoxazole, challenges for <em>Cyclospora</em> case investigations include an under-ascertainment of cases and under-reporting where case follow-ups may not be done routinely. Prof. Chalmers also noted that the time for sporulation before the <em>Cyclospora</em> oocysts become infective, and long incubation period (the time between ingestion and symptoms occurring) contributes to poor recall in identifying exposure risks.</p>
<p>International collaboration is needed for outbreak investigation and prevention which can often be challenging, while a lack of priority for analytical epidemiology particularly about potential vehicles of infection and traceability is another barrier to effective management of <em>Cyclospora</em>.</p>
<p>From a consumer perspective, Prof. Chalmers explains that the context for <em>Cyclospora</em> is mainly travel-related and so travellers should follow good food and water hygiene advice at all times on holiday, particularly in tropical and subtropical areas, even if staying in high-end, all-inclusive resorts.</p>
<p>Public health advice also includes to avoid food that cannot be washed in treated water or cooked; to only use bottled or treated water for drinking and cleaning teeth; and to avoid ice in drinks unless from a treated water source. Where possible, travellers should avoid buffets and choose freshly prepared, thoroughly cooked food that is served piping hot.</p>
<p>Prof. Chalmers also highlights how drinks may contain uncooked herbs, vegetables or fruit and encourages people to get medical advice for any symptoms, either during the holiday or after their return, and remember to tell their GP about their travel history.</p>
<p>Despite the risks, fresh produce remains the cornerstone of a healthy, sustainable diet. For most people, and especially those not in at-risk groups, the health benefits of consuming regular servings of fruit and vegetables are likely to outweigh any risks. But along the supply chain, there are actions to be taken by all parties that can help keep that risk as small as possible. </p>
<p> </p>
<p>By Journalist Nick Hughes</p></div>Contamination issues: Which foods are prone to which pathogens? And why? (June 2021)https://safefoodkn.ning.com/food-safety-thought-leader-articles/contamination-issues-which-foods-are-prone-to-which-pathogens-and2021-06-03T11:40:14.000Z2021-06-03T11:40:14.000Zsafefood Knowledge Network https://safefoodkn.ning.com/members/safefoodKnowledgeNetwork<div><p><strong>By Roy Betts, Fellow at Campden BRI, UK</strong></p>
<p><img class="align-center" src="{{#staticFileLink}}9029324662,RESIZE_400x{{/staticFileLink}}" width="200" alt="9029324662?profile=RESIZE_400x" /><br /> When microbiologists are asked to do microbiological testing, they often begin by asking themselves one simple question: “What should I test for?”</p>
<p>Why this question? <br /> Specific microorganisms can be associated with specific food categories and origins, so understanding which organisms are present can provide an indication of what’s leading to a contamination issue.</p>
<p>With over 35 years’ experience as a food microbiologist at Campden BRI, here I’ll detail how identifying the microorganism present in specific food categories, through testing, can help you understand the potential root cause of contamination. Of course, we know that testing does not and will never assure safety. Safety is managed through correct risk assessment and implementation of HACCP, but testing can provide a useful adjunct to this, helping to verify that these systems are operating well.</p>
<p><br /> <strong>Identifying microbiological issues with testing: A microbiologist’s thought process</strong><br /> Let’s return to the question of, “What to test for?” <br /> Although basic, this general question requires a huge amount of knowledge, expertise and wisdom to answer. We must also consider why a series of microbiological tests are being done. Is it for routine monitoring, hygiene determination in production, HACCP verification, or as a search for an ongoing incident with a spoilage organism or pathogen?<br /> This helps us to determine what to test for and where to test. Next, we must consider the item(s) being tested. What type of food or ingredient are we looking at, where did it come from, how was it produced and how is it going to be used? This will play a major part in allowing the microbiologist to determine the risk of certain pathogens (disease-causing microorganisms) being present and the correct tests to set up. When we are considering pathogen tests, it is also critical to understand the legislation in the country of production and the country of sale of any food item. Are any pathogen tests mandatory in the country of production or sale?</p>
<p><strong>Homing in on the organism</strong> <br /> When it comes to defining pathogen testing, we must ask more questions:<br /> • What organisms are we likely to find in particular foods and ingredients?<br /> • Which of these will constitute a risk to consumers? <br /> • Which may survive in particular conditions or retain the ability to grow?<br /> • Which have caused problems in the past?<br /> If we start by looking at various groups of foods, we begin to see the information required in the decision-making process. This depends on good microbiological knowledge, an understanding of foods, their properties and their methods of production and a good share of historical understanding of what has caused issues here before.<br /> We should also remember that the food is just an ecological environment to the bacteria contained on and within it. So, changes we make to the food will probably impact its microflora - changing those that survive, those that can grow and potentially changing the risk to the consumer.</p>
<p><strong>Meats</strong><br /> Let’s start with raw meats. These will generally have a high water activity (a<span style="font-size:8pt;">w</span>) and few controlling factors that will limit microbial growth. Within an intact animal, whole muscle will virtually always be sterile. Raw meats become contaminated during the slaughter and butchering process, potentially from the hide or gut contents. Hides may carry various types of environmental contamination, namely faeces, hence why our major organisms of concern will include enteric pathogens such as <em>Salmonella</em> and pathogenic <em>Escherichia coli (E.coli)</em>. If we’re investigating raw poultry, we may discount pathogenic <em>E.coli</em> due to the little evidence of it causing problems in this food. But we may add in <em>Campylobacter</em> as it’s commonly linked to poultry meat in food poisoning cases. Chilling correctly will slow or stop enteric pathogen growth but will not eliminate these organisms.<img class="align-right" src="{{#staticFileLink}}9029325652,RESIZE_400x{{/staticFileLink}}" width="300" alt="9029325652?profile=RESIZE_400x" /><br /> Of course, most raw meat will be cooked before eating, and this - if performed properly with a validated cook process - will eliminate these organisms. However, we still must consider the risks associated with kitchen cross-contamination from raw meat to ready-to-eat (RTE) products and the small amounts of raw meat that may be deliberately consumed undercooked.</p>
<p><br /> Turning away from raw meats, we face issues even with those that are cured – albeit different issues. Water activity (a<span style="font-size:8pt;">w</span>) measures the amount of water available in a food. A higher value for a<span style="font-size:8pt;">w</span> means that here is plenty of moisture for microbial growth, whereas a lower value indicates that there may not be sufficient water available to support the growth of bacteria. Curing salts will often reduce the aw of cured meat, but as long as this is above 0.88, bacterial growth is possible. Lower aw will, however, reduce the types of species that can grow.</p>
<p><br /> What about the enteric, faeces-originating pathogens, such as <em>Salmonella</em> or Shiga-toxin producing <em>E.coli</em> (STEC)? We may still have concerns about these, but less concern with their growth. However, we may start to consider organisms more capable of growth at low water activities. Classic ‘culprits’ would include enterotoxin-forming<em> Staphylococci</em> and <em>Listeria</em>. While<em> Staphylococci</em> will be prevented from growing at chilled temperatures,<em> Listeria</em> will continue to grow slowly even in chilled conditions. If the temperature is poorly controlled, some <em>Staphylococci</em> will grow and may form a pathogenic toxin that is very heat resistant and not eliminated by cooking, therefore it will remain active long after the organism has been killed.</p>
<p><br /> Ready-to-Eat (RTE) cooked meats offer a different challenge. If well produced in a hygienic environment, these should have been rendered free from enteric pathogens by the validated cooking process used. However, such items will then be subject to handling in a chilled “high-risk” environment. These areas can often home to<em> Listeria</em> that can thrive under cold, damp conditions and can be particularly difficult to eliminate from even the most hygienically operated production plants.</p>
<p><br /> Often, RTE cooked meats will be packed in low oxygen modified atmosphere or vacuum packs. As in any low oxygen environment, the hazard that must be considered is that posed by anaerobic bacteria, particularly <em>Clostridium botulinum</em> (<em>C. botulinum</em>) and its potent toxin. The growth of this organism must be controlled in such foods. The other <em>Clostridium</em> species to note in cooked meats is <em>C. perfringens</em>. Its spores will survive normal cooking processes but can germinate and grow during cooling, producing high numbers of vegetative cells which, if consumed, will cause food poisoning. Rapid cooling of such meats is critical to prevent growth and control the risks associated with this organism.</p>
<p><strong>Fish and seafood products</strong><br /> Microbiological hazards associated with fish will depend on the product type and how it is produced. Raw fish may be caught at sea or farmed, but after harvest, temperature control will be critical in reducing microbial risk. Even if a fish is going to be fully cooked before consumption, some types (the scombroid fish) can allow production of histamine due to <em>Enterobacteriaceae</em> growth. When consumed, this organic compound will cause histamine poisoning. Worst still, histamine will remain after cooking, meaning the only control is prevention of microbial growth after the catch.</p>
<p><br /> Fish have also been associated with <em>C. botulinum</em> toxin poisoning. It’s presumed that muds at the base of many bodies of waters may have anaerobic conditions which would explain the origin of this potent pathogen on fish. Storing fish products containing this organism under low oxygen conditions would subsequently allow the growth of C. botulinum and production of its toxin. So, how can it be controlled? In short, good temperature control will minimise the ability of <em>C. botulinum</em> to grow. Temperatures below 10°C will prevent proteolytic<em> C. botulinum</em> from growing, whereas non-proteolytic <em>C. botulinum</em> will have to be subjected to temperatures below 3°C to prevent growth. Overall, this organism must be considered a risk in fish (raw or cooked) that is going to be vacuum or modified atmosphere packed and marketed under chilled conditions.<img class="align-right" src="{{#staticFileLink}}9029325697,RESIZE_400x{{/staticFileLink}}" width="400" alt="9029325697?profile=RESIZE_400x" /></p>
<p><br /> <em>Listeria</em> is another threat that must be considered. Processed fish and fish products may become contaminated by Listeria that originates in the processing area, particularly if the fish is destined to be consumed raw, such as smoked salmon. Finally, another consideration for fish is contamination with Vibrio species; in such cases, testing for this group may be considered.</p>
<p><br /> Shellfish are filter feeders and may contain any pathogen present in the water in which they are found. Enteric bacteria and viruses such as Hepatitis A, E and Human norovirus must be considered. Cooking can eliminate these organisms, but in the case of Hepatitis A, the cook temperature may be recommended to be higher than that we would normally use for other food types.</p>
<p><strong>Dairy products</strong><br /> Raw milk may be contaminated with a variety of human pathogens that will originate from the animal. <em>Salmonella</em>, pathogenic <em>E. coli</em> and <em>Campylobacter</em> have all caused outbreaks linked to raw milk. For products made with raw milk, these key pathogens may still present a threat, but then we also start to think about <em>Listeria</em> which is often associated with chilled dairy products, and again the toxin forming <em>Staphylococci</em> in products with a lower a<span style="font-size:8pt;">w</span>.</p>
<p><br /> The correct pasteurisation of milk and prevention of recontamination from raw milk will eliminate enteric pathogens. Our focus, therefore, shifts to the production area and the environmental contaminants that could get into the pasteurized product due to poor hygiene. Fermented dairy products may have both a low pH and sometimes a reduced a<span style="font-size:8pt;">w</span> helping to control bacterial growth. Yet, Listeria may still be a real issue, surviving well in chilled production areas and able to grow at lower water activities.</p>
<p><strong>Produce</strong><br /> Produce covers a wide array of different foods. Lettuce, tomatoes, beans, potatoes, cabbage, carrots, cucumbers, onions, fruits etc. all fall into this category. Many will be grown in an open, outdoor environment exposed to all the natural animal inhabitants, and some may come in contact with the soil.<br /> Any product that is grown outdoors and may have contact with soil must be considered a risk with respect to enteric pathogens - predominantly <em>Salmonella</em> and pathogenic <em>E. coli.</em> These may arise from the soil, from animals (both ground-dwelling and birds), and irrigation waters. There have been food poisoning outbreaks traced to zoonotic contamination of field crops, either by direct contact or from faecally-contaminated irrigation water that is sprayed onto crops. We should also not discount crop contamination from humans - in the form of those tending or harvesting crops - which may contaminate produce with viral pathogens such as Norovirus and Hepatitis A.</p>
<p><br /> As well as produce that is directly harvested and sold, there is also produce that receives further treatment before sale as an RTE product to the final consumer. The production of RTE salad packs involves harvest, then usually some form of washing to remove soils and will also have a microbial reduction effect. Produce may then be cut/shredded before packing. These activities introduce factory-style activities in a chilled wet environment and start to increase concerns about Listeria contamination. <br /> Sprouted seeds are another type of fresh produce that may be considered. Seeds such as alfalfa or mung bean, are steeped in warm water for periods<a href="{{#staticFileLink}}9029326468,RESIZE_710x{{/staticFileLink}}"><img class="align-right" src="{{#staticFileLink}}9029326468,RESIZE_400x{{/staticFileLink}}" width="400" alt="9029326468?profile=RESIZE_400x" /></a> of many hours to allow germination. Of course, these are ideal conditions for microbial growth and, if the seeds harbour pathogens such as <em>Salmonella</em> or pathogenic <em>E. coli</em>, then high levels of pathogenic growth could occur. Some very large outbreaks have been traced to contaminated sprouted seeds that are consumed raw.</p>
<p><strong>Dry (Low a<span style="font-size:8pt;">w</span>) materials</strong><br /> This covers a wide range of materials ranging from dairy powders, chocolate, snack products, cereals and nut butters to herbs and spices. The key thing about organisms in dry environments is that they cannot grow. However, it also means they’ll be extremely resistant to various antimicrobial activities, such as heating, and will survive for very long time periods. The organisms that may be found in such materials will depend on how they have been produced and processed but are likely to be varied. A full risk assessment of their production method will help determine the potential hazards.<br /> If untreated, herbs and spices will contain a microflora similar to that of fresh produce (potentially including enteric pathogens). This may be considered acceptable if they are added to products before a validated cooking process is used, but completely unacceptable if added as a garnish to ready-cooked products. Chocolate and nut butters have been associated with <em>Salmonella</em> outbreaks presumably occurring through cross-contamination during production. Dairy powders likewise have been associated with <em>Salmonella</em>, and - in the special case of powdered infant formula - <em>Cronobacter</em> must also be considered an issue. <br /> Spores are often present in high numbers in dry materials; they can form a resistant state that survives drying and will remain able to germinate even after a long period. Spores are not a particular issue within the dry material unless they have grown to high numbers before the drying process has occurred. In such cases, spore formers such as <em>Bacillus cereus</em> may have produced emetic toxin which:<br /> • is very heat resistant, <br /> • will survive heating processes, and<br /> • can cause food poisoning when consumed.<br /> Likewise, the end-use of dried materials needs to be considered with respect to spore loading. Whilst stable in their dry state, as soon as a dry material is wetted the spores will germinate and grow and may cause problems in foods that use these as ingredients.</p>
<p><strong>Ready meals</strong><br /> Chilled ready meals are a large and varied market. The microbiological hazards depend on the ingredients and methods of manufacture – and these hazards can be defined by a risk assessment for each product. Generally, due to the chilled nature of these product’s production, <em>Listeria</em> must be considered a potential problem. Often <em>Salmonella</em> will also be considered; however, cooking processes and hygienic production that prevents cross-contamination will usually have eliminated this organism, and testing will be used as a HACCP verification activity.</p>
<p><strong>Final thoughts</strong><br /> Attempting to define which organisms may present a clear risk in foods is a challenging pastime. It will depend on how the food is grown, harvested, handled, processed, and packaged. It will change as different ingredients are added and if it is presented to consumers as an RTE or a ready to cook product. This article is not exhaustive and is certainly not a guide to what to test for or consider as a risk in all food products. Instead, it simply provides a food microbiologist’s view on how such an issue may be approached, some of the thought processes that can be used (based on a good knowledge of the biology of the organism), and of the type of processes used in producing foods. Each food is different, each factory is different, and each assessment of hazards and risks is different. <br /> If there is ever doubt that the correct hazards have been identified, then producers should contact an experienced food microbiologist that can help them in their ongoing quest to produce the safest foods with the lowest risk.</p></div>