Patulin is a naturally occurring mycotoxin, a toxic secondary metabolite produced by certain types of mold. Its presence in food products is generally regarded as an indicator of poor quality raw materials and inadequate handling during processing. Because patulin is resistant to common processing methods, its control requires strict management from the farm to the final product stage.
Patulin: A Definition and Classification
Patulin is a mycotoxin produced mainly by species of fungi belonging to the Penicillium and Aspergillus genera. The most common source is Penicillium expansum, which causes blue mold rot in various fruits. The substance itself is a colorless, crystalline, polyketide lactone.
A significant chemical property is its stability under high heat and acidic conditions. This stability means that standard pasteurization used for fruit juices can kill the mold but will not eliminate the patulin already present in the liquid. Patulin is also highly soluble in water, which allows it to easily diffuse from infected fruit tissue into liquid products.
Where Patulin Contamination Occurs
Patulin contamination is overwhelmingly associated with apples and products derived from them, such as apple juice, cider, and apple sauce. The mold responsible for patulin production, primarily P. expansum, requires a breach in the fruit’s skin to gain entry. This damage can result from insect activity, physical bruising during harvesting, or improper handling and storage.
Once the fungal spores enter a wound, the mold proliferates and produces the patulin toxin in the rotting tissue. The toxin then spreads from the visibly damaged area into the surrounding, seemingly healthy flesh of the fruit. Contamination risk is particularly high in apple juice because a single rotten fruit can contaminate an entire batch during the pressing process.
While apples are the major source, patulin has also been detected in other fruits, including pears, peaches, apricots, and certain grains. Cold storage can slow the growth of the mold, but it does not stop the production of patulin entirely, especially if the fruit was damaged before being stored.
The Health Effects of Patulin Exposure
Patulin is classified as a toxic compound that primarily exerts its effects by reacting with sulfhydryl groups in proteins, which interferes with cellular enzymes. Acute exposure to high concentrations of patulin in humans can lead to symptoms of gastrointestinal distress. These effects typically include nausea, vomiting, and irritation of the digestive tract.
Although severe poisoning is rare in humans due to existing food controls, chronic exposure has been linked to concerning effects in animal studies. Patulin is considered genotoxic, meaning it has the potential to damage DNA, although its carcinogenic potential in humans remains inconclusive. High-dose animal studies have also indicated potential for immunotoxicity and neurological effects. The World Health Organization (WHO) has established a provisional maximum tolerable daily intake (PMTDI) to guard against these long-term risks.
How Food Safety Regulations Limit Patulin
Food safety authorities around the world regulate patulin levels to protect consumer health, particularly for susceptible populations like children. The most effective method of control involves diligent quality assurance of the raw fruit used in processing. Good Manufacturing Practices require that all damaged, bruised, or visibly moldy fruit be rigorously sorted and removed before processing begins.
Regulatory bodies establish maximum permissible limits (MPLs) for patulin in finished products. For apple juice and cider, the European Union (EU) and the U.S. Food and Drug Administration (FDA) have both set an action level of 50 micrograms per kilogram (µg/kg). A much stricter limit of 10 µg/kg is enforced in the EU for juices and foods specifically intended for infants and young children.