Patulin is a mycotoxin produced by numerous moulds, in particular Penicillium, Aspergillus and by Byssochlamys species.
It is a common contaminant of fruit and vegetable fruits, often present in rotting apples and apple products, as a result patulin has frequently been found in commercial apple juice.
Tannous, Joanna & Keller, Nancy & Atoui, Ali & el Khoury, Andre & Lteif, Roger & Oswald, Isabelle & Puel, Olivier. (2017). Secondary Metabolism in Penicillium expansum: Emphasis on Recent Advances in Patulin Research. Critical Reviews in Food Science and Nutrition. 58. 10.1080/10408398.2017.1305945.
The abundant nature of patulin producers, which comprise at least 60 different species of fungi, is reflected its presence in many different foods.