Mould can give cured meats a poor appearance, taste, texture and aroma and can reduce safety. Mould can be the cause of production loss through poor quality and increased production costs. Pathogenic yeast fungi and toxic mould fungi can be the cause of health problems among consumers. Producers must take the problem seriously.
These are whole pieces of meat that have been salted, cured and dried and that may be smoked or unsmoked, such as hams or the Norwegian fenelår or cured leg of lamb. Demand for high quality cured meats is increasing steadily.
Italy and Spain are world leaders in such products, but production of high quality cured meat is also increasing in the Nordic countries. The quality of cured meat is defined from its appearance, taste, texture, aroma and food safety. These will be affected by both raw materials and production conditions. A common quality problem among many cured meat producers is the growth of mould.
What is mould?
Mould is a microscopic fungus, usually growing with a thread-like appearance. These threads are caller hyphae. The hyphae create colonies that vary in size from microscopic to easily seen flecks. Mould fungus has a fascinating diversity of shape and colour, both through the microscope and what we can see with the naked eye. Mould is found in air and water throughout our everyday environment, including in places where food is produced.
Moulds are part of nature’s organisms for decomposition. Broadly speaking, mould fungi can be divided into two groups: storage moulds and field moulds.
Storage mould fungi grow on dead material during the storage of food and animal feed, unlike field mould fungi that mainly grow on living plant material out in fields and meadows.
Most mould fungi must have oxygen in order to grow, although there are some that can grow with very little oxygen. Mould can grow over a wide range of temperatures (-7°C to 58°C). The optimum temperature for growth is around 25°C for the most common mould fungi. Depending on species, they grow as white, green or greyish-brown flecks on organic material.
Useful and damaging mould fungi
Mould can be useful in food production and in medicine. Two examples are Penicillium roqueforti, which is used in cheese production, and Penicillium chrysogenum, which makes penicillin. It is more common however for mould to reduce the quality and safety of different foods.
Mould can give food a poor appearance, taste, texture and aroma. Mould can also be the cause of disease in animals, people and plants. Mould can also be toxic, because it can produce mycotoxins.
Mycotoxins are metabolic products that are not necessary for the growth of the fungus, but that are used to compete with other micro-organisms and to communicate with other fungi.
They are toxic to vertebrates in low concentrations when introduced in a natural manner, that is to say eaten, breathed in or absorbed through the skin.
Effect of mycotoxins in food
Mycotoxins are undesirable in food because they can have negative effects on most of the body’s organs, including the nervous system, the immune system, the liver, the kidneys, the digestive system and the respiratory organs.
Mycotoxins can lead to serious acute or chronic illness. Some can cause nausea and diarrhoea, while others lead to less clear cut symptoms, like listlessness and a general feeling of being unwell. Some mycotoxins can be carcinogenic.
Factors that affect the creation of mycotoxins
The creation of mycotoxins in food is dependent on many factors, so that the growth of a mould fungus that could produce mycotoxins will not necessarily lead to the toxins actually being produced. Important factors for the production of mycotoxins are optimum temperature, optimum water activity and access to nutrients and oxygen. Most mycotoxins can tolerate physical and chemical treatment and are odourless and tasteless. Generally speaking, once mycotoxins have appeared in food, they remain in it throughout processing and storage.
Types of mould that contaminate cured meat products
Mould fungi can be found in most production premises for cured meat and can easily infect products during production. Moulds that affect cured meat products are those that thrive on foods with low water activity (aw) (xerofile). Studies from various countries show that most mould fungus species that are connected with cured meat products are members of the Penicillium, Aspergillus and Eurotium families.
Some of the species in these geni are toxic. They can create mycotoxins that can make food products both inedible and hazardous to health. It is therefore important to have control over which species are growing on the products. Some species from the genus Cladosporium have also occasionally been isolated from cured meat products.
Normally only a few fungus species are strongly associated with growth on and spoiling a particular product. We call these the product’s associated flora. Usually a product’s associated flora will consist of fewer than ten species of fungus. In food production it is absolutely essential to identify a product’s associated flora and keep it from accidental contamination.
Mould should be taken seriously
Generally the quality of cured meat products will be reduced by the growth of mould. Cured meat products contaminated with pathogenic yeast fungi and toxic mould fungi can be the cause of health problems among consumers. This could lead to producers losing regular customers and having problems finding new ones. This means that the growth of mould could give cured meat producers serious financial problems and the producers must be careful to treat and follow up on fungus related quality problems.