C03005: Reducing patulin in apple juice through manipulation of orchard practices

Study Duration: June 1998 to May 2001

Contractor: ADAS, RSSL, CABI Biosciences, Imperial College

Patulin is a mycotoxin produced by the fungus Penicillium expansum, which has been shown to have mutagenic properties. Patulin can be present in pressed apple juice and there is an advised maximum level of 50 parts per billion (ppb). In some cases batches of apple juice may exceed this threshold and have to be discarded.

This research project was undertaken to find out if there is a relationship between farm practices in orchards, and patulin levels occurring in fruit from those orchards when it is processed. If a connection is found between fungicide usage and patulin occurrence then advice can be given on reducing the risk.

Initially, orchards where processed fruit contains patulin will be identified. The practices in these orchards will then be compared with those in orchards where patulin problems are not found. This work will involve the development of artificial media to aid the isolation and identification of penicillium species from the orchards and fruit stores. The direct effect of fungicides on penicillium in culture will be examined to see which ones control the growth of the fungus, and to establish whether they have any direct effect on the level of patulin production. This will be measured by a laboratory assay developed as part of the project.

Several strains of the fungus Penicillium expansum are known to produce the neurotoxin, immunotoxin, and potential carcinogen, patulin.

This project aimed to determine the location of P. expansum in an orchard environment; to determine if commercial orchard practices affect the levels of patulin in juice processed from apples originating in the orchard; to develop a molecular method of detecting the presence of the gene for patulin production in fungi; and to see if any of the fungicides used in commercial orchards might affect the production of patulin in penicillium isolates.

The findings were as follows:

• P. expansum was detected in orchard soils, debris on the orchard floor, on various parts of the apple tree (bark, leaves and fruit) and in the mature fruit core. It was also detected in the atmosphere of apple stores and in the flotation water used in a packhouse grading system.
• P. expansum was more readily isolated from leaves, bark and fruit from trees in an orchard where fungicides had not been used for many years.
• However, in general, no relationship could be established between fungicide usage in the ten orchards examined in detail and patulin levels in juice from the processed fruit. The single exception was a possible connection between the use of dithianon during the blossom period in the spray programme which, as compared to captan use during this period, appeared to be linked to higher patulin levels. This finding needs further investigation.
• The development of the polymerase chain reaction (PCR) probe allowed detailed work to be carried out on detecting the presence of the gene for patulin production in Penicillium brevicompactum, Penicillium paxilli and Penicillium roquefortii, as well as P. expansum. In the three former species the gene was non-functioning in the isolates examined.
• With some P. expansum isolates, the presence of some fungicides in the agar medium affected the level of patulin production in vitro. In most cases where the fungicide influenced patulin production there was a suppression of production, but in the case of vinclozolin production appeared to be stimulated. Further studies in this area would be worthwhile.
• When fruit is removed from storage and processed quickly, patulin was rarely detected. When fruit was deliberately left at ambient temperatures for 7 or 14 days before processing, patulin levels increased. This result confirms existing reports regarding the need for rapid processing of fruit once it comes out of controlled storage conditions.

The final report is available from the Agency's Information Centre. To obtain a copy, please contact the Enquiry Desk, Information Services, Food Standards Agency (tel: 020 7276 8181/8182 or email: infocentre@foodstandards.gsi.gov.uk)

Contact: For any enquiries concerning this research project, please contact the relevant programme contact or email: science@foodstandards.gsi.gov.uk