Moulds in Food


Moulds widely occur in the nature and are found in the air, water and soil. As a coastal city like Macao, characterised by high temperature, high humidity and abundant rainfall, it provides the favourable conditions for mould growth.


Moulds are one of the diverse categories of fungi which also include yeast, mushrooms and rust fungi. Moulds can grow at refrigeration temperature continuously. When its presence is spotted on food, it is a sign of food spoilage.


Moulds produce tiny spores to reproduce, which are invisible to the naked eye and spreading by air, water, food handling or other means. Once a spore lands on a suitable place like food, it germinates. When it grows to form a large mould colony, it becomes noticeable to human eyes. Yet, at times we may not notice that the food is already mouldy, especially when the colour of the moulds is similar to the food. For instance, greyish spots are readily visible on a white bread but would be hardly noticeable on a dark chocolate cake. It is possible that we may have eaten food contaminated with moulds without realized!


Is mouldy food dangerous?

In reality, some mould species are harmless. For instance, the unique flavours of many blue cheeses, like Roquefort, come from a specific penicillium added during the manufacturing process. The famous ‘Hairy Tofu’ of Huizhou in China is in fact the mildewed bean curd, which has a layer of mycelia on its surface. It is believed that the hairy moulds have given the bean curd distinctive flavour.


However, some other mould species can cause infections, particularly in people with weak immunity, like those suffering from chronic diseases. Some moulds are capable of producing mycotoxins which can cause acute and/or long-term health impacts on humans. For an example, aflatoxins may cause acute liver damage, and it is well-known for potentially inducing liver cancer.


Aflatoxins are a kind of mycotoxins that are mostly produced by Aspergillus flavus. It is green to the naked eye, but the aflatoxins it produces are colourless, tasteless and odourless.


Aspergillus flavus can grow in soil and produce aflatoxins under aerobic and humid conditions at higher temperature (at 28-33 in general). Aflatoxins are commonly found in a variety of crops, such as peanuts, maize, cereals and their products. The toxins may also be present in dairy and meat products; since, it can accumulate in the animals’ body through their consumption of contaminated feed. These are heat-stable and unable to be destroyed by cooking.


Health Effects

Consumption of aflatoxins contaminated food is a main hazard to human health, which can cause acute and chronic health impacts.

  1.  Acute Impact: Ingestion of high doses of aflatoxins within a short period of time may result in acute food poisoning, but this rarely happens in developed countries. The symptoms include fever, vomiting and jaundice. More severe cases may lead to liver damage or even death.
  2. Chronic Impact: Trace amounts of aflatoxins may be present in food and intake for long time may cause liver cancer.

How to reduce the food safety risk of mycotoxins?

It is impossible to totally eliminate mould growth on food; so, it is necessary to take control measures in order to reduce mycotoxins in food and feed to a reasonably low level as much as practicable. In addition to the government’s role as a gatekeeper, ensuring food safety is also required the cooperation and efforts among the food traders and public. In this respect, consumers should buy food products from reliable and reputable shops, and store food ingredients in dry and cool environment to reduce the chance of mycotoxins production in food. If any food ingredient shows a sign of mould growth, we must discard the food and not just cut away the mouldy parts.


What is the regulation of mycotoxins in Macao?

Besides of aflatoxins, ochratoxins and patulin are also significantly harmful to the human body. Therefore, the government has established the ‘List of Maximum Limits of Mycotoxins in Food’ (Chinese & Portuguese Versions only) in May 2016. It includes the maximum limits of aflatoxin B1, aflatoxin M1, ochratoxin A and patulin allowable found in different types of food to ensure public health and food safety.