Food Safety Focus (222nd Issue, January 2025) – Article 1
Moulds on Food – Potential Health Risks?
Reported by Dr. John LUM, Scientific Officer,
Risk Assessment Section, Centre for Food Safety
In nature, moulds can be found everywhere and are known to cause food spoilage. When bread is left at home for several days, grey patches of moulds will be readily visible on the surface, especially under the warm and humid climate of in Hong Kong. We will examine mould and its potential health risks in further detail in this article.
Potential health risk of moulds on food - Mycotoxins
Although moulds on food have an unpleasant appearance, acute toxicity resulting from the consumption of mouldy food is not common. Yet, certain moulds (e.g., Aspergillus fumigatus) can cause infections in humans, especially in patients with weakened immunity. Moreover, certain moulds can naturally produce toxic substances, known as mycotoxins, which can be harmful to humans. People can be exposed to mycotoxins directly from the consumption of contaminated foods, or indirectly from consumption of food products (e.g., milk) produced from animals fed with contaminated feed.
Figure : Various sources of human exposure to mycotoxins
Mycotoxins in food
A wide variety of mould species have been identified to produce several hundred different mycotoxins. The most well-known of these mycotoxins are aflatoxins, patulin and deoxynivalenol, which will be further discussed in the following paragraphs.
Aflatoxins
Aflatoxins are amongst the most toxic mycotoxins, most commonly found in cereals, oilseeds, spices and tree nuts. Ingesting large doses of aflatoxins can result in acute poisoning, i.e., aflatoxicosis, which could be deadly, usually through damage to the liver. Long-term consumption of food contaminated with aflatoxins can cause liver cancer, and the risk of liver cancer in individuals exposed to both aflatoxins and hepatitis B virus (HBV) infection is much higher than that in non-HBV infected individuals.
Patulin
Patulin is most commonly found in rotten apples and apple products, including apple juice. Excessive exposure to patulin has been found to cause nausea, gastrointestinal disturbances and vomiting in humans.
Deoxynivalenol
Deoxynivalenol (DON), also known as vomitoxin, is most commonly found to contaminate cereals, particularly wheat and maize. The primary health concern of DON in humans is its potential to induce acute illness, including nausea, vomiting, diarrhoea, abdominal pain and fever, within a short time after ingestion.
Regulation of mycotoxins in food in Hong Kong
In Hong Kong, regulatory limits for mycotoxins in food are stipulated in The Harmful Substances in Food Regulations (Cap. 132AF). The regulatory control of mycotoxins was further updated and strengthened in the amendment exercise of this regulation in 2021. For example, the maximum limits of aflatoxins in certain tree nuts, peanuts and dried fruit which are more susceptible to aflatoxin contamination were tightened up (from 15-20 µg/kg to 10-15 µg/kg) considering the food safety risks posed by aflatoxins to the local population. Moreover, since DON is more common in cereal food, and infants and young children are more vulnerable to the toxic effects of DON, a maximum limit (200 µg/kg) was established for food containing cereal intended to be consumed by infants and young children under the age of 36 months. For patulin, a maximum limit (50 µg/kg) was established for patulin in apple juice and other beverages to which apple juice has been added.
How to minimise the risk of mycotoxins?
Most mycotoxins are heat stable, and therefore cannot be removed by various home cooking methods, including roasting, baking and frying. As mycotoxins cannot be completely destroyed by cooking, prevention is the key to minimising our exposure to mycotoxins. Nevertheless, mould usually does not grow in properly dried and stored foods, so proper storage is an effective measure against mould growth and the production of mycotoxins. The Codex Alimentarius Commission has also issued different codes of practice for the prevention and reduction of mycotoxins in various food commodities. The Centre for Food Safety (CFS) has issued related guidelines to provide guidance for food trade producing and handling peanuts in pursuit of preventing and reducing aflatoxin contamination.
Key Points to Note
- Moulds that produce mycotoxins can grow in a variety of foods, including cereals, oilseeds, spices and tree nuts.
- Most mycotoxins are heat stable, and therefore cannot be removed by various home cooking methods, including roasting, baking and frying.
- Moulds usually do not grow in properly dried and stored foods, so proper storage is an effective measure against mould growth and the production of mycotoxins.
Advice to Consumers and Trade
- Purchase food from reliable sources and store them properly (e.g., follow the manufacturer's instructions to keep them in a cool and dry place).
- Food that looks mouldy or damaged should be discarded.
- Buy small amounts of food and use them as soon as possible to prevent food from turning mouldy.
- Follow the corresponding Guidelines issued by the CFS and international authorities.
- Maintain a balanced and varied diet to avoid excessive exposure to contaminants, including mycotoxins, from a small range of food items.