Nutritionist > Dairy

Patulin
Patulin is a polyketide lactone, produced by certain fungal species of Penicillium, Aspergillus and Byssochlamys growing on fruit, including apples, pears and grapes. Patulin was first isolated in the 1940's but is now known to occur world-wide in apple and apple products.

In whole fruits, a visual inspection will usually identify poor-quality items. Patulin is particularly associated with apples exhibiting "brown rot" or other rotting characteristics. Any fruit with visible signs of rotting, decay or mould growth could be suspect and could contain patulin.

The principal risk arises when unsound fruit is used for the production of juices and other processed products. Contamination with patulin has also been reported in vegetables, cereal grains and silage. Patulin is not considered a particularly potent mycotoxin.

Fruits stored under conditions that promote bruising and rotting increase the probability of patulin formation. Penicillium expansum appears to be the mould usually responsible for patulin in apple juice.

Patulin can be isolated as colourless to white crystals. It is soluble in water, methanol, ethanol, acetone, and ethyl or amyl acetate and is less soluble in diethyl ether and benzene. It is stable in acid solutions but can be decomposed by boiling in 2N H₂SO₄ for six hours. It is susceptible to alkaline hydrolysis, reduced by SO₂ and by fermentation (storage).

Patulin possesses broad-spectrum antibiotic properties and has been tested to evaluate its ability to treat common colds. However, its effectiveness has never been proven and, in the light of its toxicity, use for treatment of medical conditions has not been pursued because of it being an irritant to the stomach and causing nausea and vomiting.

Symptoms of patulin toxicity include haemorrhaging in the digestive tract in cattle. In 1954 patulin was implicated in the deaths of 100 cows in Japan that ate contaminated feed.

For patulin, the LD₅₀ in rats has been reported as 15 mg kg¹ body and 25 mg kg¹after sub-cutaneous injection. Death was usually caused by pulmonary oedema. In long-term studies at lower dosage levels, these effects were not observed. It has also been shown to be immunotoxic, and neurotoxic. Several studies have found that patulin is genotoxic, i.e. that it causes damage to DNA or chromosomes, in short-term studies. However, these studies were performed in bacterial or mammalian cell cultures and with doses of the toxin that are not relevant to human exposure levels.

Based on reproduction, and long-term carcinogenicity studies in rats and mice, the JECFA allocated a Provisional Tolerable Weekly Intake of 7 µg/kg b.w.

Co-contamination and further mycotoxins
Contaminated feeds or ingredients typically contain more than one known and probably several unknown mycotoxins. The toxic responses and clinical signs observed in ruminants when more than one mycotoxin is present in feed are complex and diverse.

Co-contamination of mycotoxins appears to exert greater negative effects on health and productivity than single mycotoxins. For this reason, symptoms typical of mycotoxicosis are often seen in ruminants despite analyses of the feed indicating only very low concentrations of individual mycotoxins. Toxicity may be due to interactions between different mycotoxins that exaggerate the toxicity symptoms.

With mycotoxins the risk directly depends on the level of the major mycotoxins in the feed, the co-occurrence and level of other mycotoxins, the age of the animal and the health status. Therefore strictly speaking it is not possible to define safe levels of mycotoxins. This complex situation makes it necessary to take all relevant precautions.

Sampling and testing for mycotoxins
Due to the uncertainties associated with any mycotoxin testing procedure, it is very difficult to determine the true mycotoxin concentration of a bulk lot. Mycotoxins are difficult to measure for a number of reasons:

• Many different mycotoxins can be present simultaneously, making analysis difficult and expensive. Under commercial conditions an analysis is normally limited to a couple of indicator mycotoxins.
• Sampling of bulk feeds is difficult. Mycotoxins are present in 'hot' spots and are not evenly distributed throughout the feed. Therefore strict sampling procedures should be followed with many samples taken from a particular batch to get a realistic reading.
• Latest research has identified complex mycotoxins which do escape routine analyses.