In the 30 August 2020 episode of YSN-ASM Science Café KL, Shawn Keng introduced us to Associate Professor Dr John Tang Yew Huat. Dr John completed his Masters in Microbiology from Universiti Kebangsaan Malaysia (UKM) and subsequently his Doctoral Degree in Food Safety from Universiti Putra Malaysia. Currently, he is a Senior Lecturer at the School of Food Science, Universiti Sultan Zainal Abidin (UniSZA). Dr John shared the importance of understanding food safety, food poisoning and how it affects our everyday life.
The Food and Drug Administration (FDA) ‘s definition of food poisoning states: foodborne illness (commonly known as food poisoning) is often caused by consuming food contaminated by bacteria and other toxins, parasites, viruses, chemicals, or other agents.
Causes of Food Poisoning
Food poisoning may arise due to the following causes:
- Microorganisms: Bacteria, viruses and other pathogens that enter the body and multiply, causing harm to the body.
- Microbial toxins: compounds secreted by bacteria; may also be heat-stable, rendering cooking useless to eliminate it.
- Chemicals: may be naturally-occurring, or human-made, e.g. food additives, industrial wastes or pesticides. Some common possible poisonous substances are arsenic, lead, and mercury. Mycotoxins are an example of natural chemicals that may cause poisoning, which is produced by fungi.
Next, Dr John elaborated on chemical food poisoning. A common source of chemical-based food poisoning arises from pesticides. Undoubtedly these chemicals help to prevent pests from ravaging crops, but the residues might be harmful to humans. Food additives that are prevalent in today’s processed food may also cause foodborne illnesses. The presence of heavy metals such as lead, arsenic and mercury from industrial waste may also pollute food sources and bring harm to humans. Aside from human-made sources of harmful chemicals, natural chemicals may also cause food poisoning, such as mycotoxins. Mycotoxins are a toxic secondary metabolite produced by organisms of the fungus kingdom and is capable of causing disease and death in both humans and other animals.
Next, Dr John elaborated on biological causes of food poisoning. Three most common biological food poisoning pathogens are norovirus, parasites and bacteria. These pathogens may be transferred from its source to the food via contact with an infected person, or they may already be present in raw food due to improper handling and incomplete cooking. Contamination may also occur when mixing raw and cooked foods. Besides, not keeping foods at the right temperature may also encourage the pathogens to grow. When these contaminated foods are consumed, it causes food poisoning.
Dr John also explained food spoilage, a complex process that involves intrinsic parameters (e.g. type of product) and extrinsic parameters (e.g. how the product is packaged and stored). These parameters are select for the variety of spoilage microorganisms that can grow quickest under those parameters, causing the product to be spoiled. By adjusting these parameters, spoilage can be slowed down, reducing the chances of food poisoning. Dr John taught viewers how to identify spoiled food by using the senses:
- Smell: take a whiff of the food, whether it has an odd smell.
- Sight: look at the food to identify if there are physical signs of spoilage (mould, discolouration, etc.). Note that sometimes, food may look okay, but its smell gives away its spoilage.
- Taste: if it smells okay, looks fine, but maybe its taste will give away the fact that the food is spoiled.
Spotting Contaminated Food
Pathogens such as bacteria are microscopic and cannot be seen with the naked eye; therefore, contaminated food might not be detected easily. These pathogens can duplicate rapidly depending on its species and its surrounding conditions. Malaysia’s warm and humid climate is a conducive environment for pathogens such as bacteria to grow; coupled with improper storage, these are excellent conditions for bacteria to grow and cause spillage.
Continuing the session, Dr John highlighted the worst foodborne outbreaks throughout history. One example is the salmonella outbreak in the United States that has occurred several times: 2009 (peanut butter), 2011 (ground turkey), 2013 (chicken) and 2015 (cucumbers). Salmonella is a common bacterial disease that affects the intestinal tract. Salmonella bacteria typically live in animal and human intestines and are shed through faeces. Humans become infected most frequently through contaminated water or food.
E. coli outbreaks are also common in the US, having occurred in 1993, 2006, and 2015. Escherichia coli (E. coli) bacteria typically live in the intestines of healthy people and animals. Most varieties of E. coli are harmless or cause relatively brief diarrhoea, but a few nasty strains can cause severe abdominal cramps, bloody diarrhoea and vomiting. You may be exposed to E. coli from contaminated water or food, especially raw vegetables and undercooked ground beef. Healthy adults usually recover from infection with E. coli within a week. Still, young children and older adults have a greater risk of developing a life-threatening form of kidney failure called a hemolytic uremic syndrome.
The US also experienced several listeria outbreaks throughout the years, in 1985, 1998-1999, 2002 and 2011. Listeria infection is a foodborne bacterial illness that can be very serious for pregnant women, people older than 65 and people with weakened immune systems. It is most commonly caused by eating improperly processed deli meats and unpasteurized milk products.
Malaysia is also no stranger to several foodborne outbreaks. There was a 23.69% increase in food poisoning cases, from 401 cases in 2018 to 496 cases in 2019. In 2018, there was a foodborne outbreak of salmonella in Kuala Lumpur via laksa noodles; a case of food poisoning via fried noodles at a school in Johor also occurred earlier this year. More recently, the case of spoiled “pudding buih” in Terengganu happened in May 2020.
Aside from E. coli, Listeria, and Salmonella mentioned above, other pathogens that can cause food poisoning, such as:
Symptoms of foodborne illnesses include:
- Nausea and vomiting
- Upset stomach
The above are common symptoms; in severe cases, foodborne illnesses might cause organ failure and blood infections.
Dr John continued his session with an introduction to E. coli. According to Dr John, most strains of E. coli are harmless; the strain that causes food poisoning is categorized as enterohemorrhagic bacteria E. coli (EHEC for short). Contracting EHEC may be life-threatening in severe cases, where the infection causes blood infection and organ failure. This strain is usually due to uncooked/undercooked meat and raw milk. Fruits and vegetables that have come into contact with faeces may also contain EHEC.
Almost any food and beverages can carry salmonella, but it is commonly found in meat and eggs. When the bacteria enters the body, it will begin its life cycle once it reaches the intestines. Salmonella could prove to be fatal when the bacteria break through the intestinal wall to enter the bloodstream.
Staphylococcus aureus (S. aureus for short) is a bacteria that lives on our skin and nasal cavity. Usually, S. aureus is not pathogenic. The bacteria is only problematic when it is transferred to high-risk food (e.g. meats with mayonnaise, cooked ham/sausages, non-meat food such as milk, cream, and pudding) via open wounds or from nasal and oral cavities. The bacteria contaminates the food, releasing toxins that cause food poisoning. This toxin is heat stable and will still cause food poisoning even though the food is reheated.
Next, Dr John explains how Bacillus cereus (B. cereus) causes foo poisoning. The bacteria are spore-forming. When conditions are suitable, this pathogen will start to germinate and multiply. Bacillus cereus is a foodborne pathogen that can produce toxins, causing two types of gastrointestinal illness: the emetic (vomiting) syndrome and the diarrhoeal syndrome. When the emetic toxin (usually from cooked rice or other starchy food left for a prolonged time at room temperature) is produced in the food, vomiting occurs after ingestion of the contaminated food. The diarrhoeal syndrome occurs when enterotoxins are made in the intestine, following ingestion of food contaminated with B. cereus (usually meat and ready-prepared meals that were improperly stored).
One of the more well-known vibrios is Vibrio cholerae (V. cholerae), some strains of which cause the disease cholera, which can be derived from the consumption of undercooked or raw marine life species or untreated water. Severe diarrhoea is a symptom of cholera, to the extent that there will be no stools present and the body will be lethally dehydrated due to loss of electrolytes.
Campylobacter is the bacteria that causes gastroenteritis, an infection of the intestines. It is commonly found in farm animals, especially poultry. Animals that carry the bacteria do not typically show signs of infection; when uncooked/undercooked meat from infected animals are consumed, gastroenteritis could result.
Apart from the common symptoms of food poisoning, other serious complications may result. The bacteria Listeria monocytogenes might cause miscarriages in pregnant women; a severe bout of Campylobacter pylori can sometimes cause paralysis due to nerve damage. The previously stated Listeria can also cause septicaemia, leading to septic shock. Also, autoimmune diseases such as Guillain-Barré syndrome can be caused by Campylobacter pylori. Guillain-Barré syndrome is a rare disorder in which your body’s immune system attacks your nerves.
How to Reduce the Risk of Food Poisoning?
It may be easy to detect spoiled food based on the previously stated ways of identification; however, contaminated food may not be as easily identified. Dr John advocates the practice of food safety, the conditions and practices that preserve the quality of food to prevent contamination and foodborne illnesses.
Conditions that support the growth of microbial pathogens can be condensed into the acronym FATTOM:
- Food: pathogens need a source of food – usually proteins or carbohydrates, which are readily available in the food you serve.
- Acidity: pathogens grow best in foods with low acidity; ingredients such as lemons and tomatoes can make food too acidic for the rapid growth of pathogens.
- Time: Pathogens need time to grow. A single bacterium can multiply into 1 billion bacteria in 10 hours.
- Temperature: Pathogens grow best between 5˚C and 57˚C.
- Oxygen: Some pathogens require oxygen to grow.
- Moisture: Pathogens need water to grow.
Using Food Labels to Ensure Quality
Dr John informs viewers to pay attention to several local and international food labels that show that food and beverages are produced up to high standards of hygiene and safety. Labels such as the Ministry of Health’s MESTI (Makanan Selamat Tanggungjawab Industri) and GMP (Good Manufacturing Practices) are examples of Malaysian standards that are given to products manufactured by Malaysian SMEs that have been produced according to the required hygiene and safety criteria. Through MeSTI certification, food manufacturing premises will be guided in developing and implementing Food Safety Assurance Program before recognition is granted.
On the other hand, GMP was established to give official recognition to industries that have achieved GMP elements and meet the requirements of food safety and consumer needs. The GMP Certification Code was launched to provide official recognition to successful food premises and to maintain the system GMP in food premises.
Another label is the HACCP (Hazard Analysis Critical Control Points). HACCP is a risk management tool primarily used to manage food safety risks. The HACCP scheme meets the requirements of the Codex Alimentarius Commission (CAC) that was established by the World Health Organization and the Food and Agriculture Organization of the United Nations to bring together international food standards, guidelines and codes of practice to ensure fair trade.
Staying Safe When Eating Out
When eating out, Dr John advises viewers to observe whether the food premise was graded with the local authority’s cleanliness grading system. According to the grading system, restaurants have to comply with specific rules to earn the proper certifications needed to operate. To ensure that these restaurants keep up with the set standards, local health inspectors will carry out checks before assigning them a cleanliness grade.
In his closing remarks, Dr John stated that while most food poisoning cases are mild and self-limiting. However, in some cases, it could become severe and lead to serious health complications or even death. Contaminated food might not show any signs of spoilage, so it is wise to inspect it using your senses before consuming. Besides that, he also stated that a small amount of food pathogens is all it takes to make you fall sick. Good food handling is necessary to prevent cross-contamination of food that leads to foodborne illnesses. Last but not least, always choose certified clean premises while eating out.