Patulin in apple juice
The processing market (juice, cider, purees, confectionary etc) represents a significant part of the overall market for apples in the UK, providing an outlet for both culinary and dessert fruit, it complements the market for fresh fruit.
In order to ensure that the processing industry continues to use UK product growers need to understand the requirements of processors and, where ever possible, provide fruit that meets their requirements.
Over recent years there has been much attention paid to patulin contamination of apple products with the UK government, in common with other countries, regularly surveying levels in processed products:
- In some UK samples relatively high patulin levels were recorded in 1992 in a small sample of juices in a limited surveillance operation, 26% of the samples had over 50µg/kg but one had 434µg/kg triggering some concern by regulators.
- Subsequent surveys showed a rapid improvement with levels of patulin, in both clear and cloudy juices, dropping and the majority of samples complying with the 50µg/kg advisory limit by 1998, however about 2% of samples were still found to exceed 50µg/kg.
- In 2001/2002 of 300 samples of mainly juices but also some baby and other apple products 1% exceeded 50µg/kg whilst over 84% of samples showed patulin at below the limit of determination (<6µg/kg).
Patulin contamination has been the subject of considerable discussion among regulators both internationally and within Europe resulting in the European Commission introducing legislation to set maximum permitted levels of patulin in apple products which became the statutory limit in the UK in 2007:
|
Patulin: EU Limits in Apple Products
|
- It is now crucial for food producers to ensure that patulin levels in their products are as low as possible and do not exceed the statutory limit.
- Exceedances of the statutory limit in apple products would have an adverse impact on the use of UK sourced fruit by processors as well as to generally undermine consumer confidence in both fresh and processed apple.
- Minimising patulin in UK fruit destined for processing will help safe guard the whole apple market.
What is Patulin
Patulin is a mycotoxin metabolite produced naturally by a range of fungal species growing on fruit especially:
- Penicillium
- Aspergillus
- Byssochlamys.
Penicillium expansum appears to be usually responsible for patulin in apples and a wide variety of other fruits including pears, peaches, banana, pineapple, apricot, cherries and grapes.
- Apples can be prone to particularly high levels of patulin.
- Normally patulin only occurs in fruit on which mould has grown although the spoilage may not be obvious.
- It is possible for the fungi to grow within the fruit, entering via insect or other damage (such as bruising) or in varieties with an open calyx to enter the core early during the fruits’ development.
- Often patulin is associated directly with storage diseases and there can be a higher risk in fruit from long term storage.
Patulin in food and drink
- Patulin can be present in juices, puree and other processed forms of apple fruit.
- When sulphur dioxide is used as a food preservative in fruit juices or other foods, patulin is broken down.
- It is not usually found alcoholic beverages or vinegar where patulin interacts with some yeasts during fermentation and is destroyed.
- In some cases ascorbic acid has been reported to cause the disappearance of patulin from apple juice.
- A major risk is patulin in direct pressed apple juices where patulin levels can be a significant problem.
Detection
The testing for the presence of patulin in fruit products requires a laboratory test, high performance liquid chromatography (HPLC) with ultra violet (UV) detection, with some other confirmatory analyses needed.
A number of attempts have been made to develop a more rapid test for use by producers but none have yet successfully reached the market.
- In theory at least it should be possible to raise suitable antibodies to patulin and incorporate these into a monitoring device and produce a “dip-stick” test or something similar. This has been achieved for other mycotoxins.
- The small size of the patulin molecule has hindered the production of suitable antibodies to date and a rapid test based on immunological principles is still awaited.
- The difficulties and cost of the test mean that only the largest processors can have testing facilities on site, smaller processors rely on others to provide this service with a consequent delay in receiving results.
Penicillium expansum in the orchard
Penicillium expansum is common, easily recognisable but not responsible for large fruit losses commercially.
- It invades fruit through wounds, bruises or cracks anywhere on the fruit surface often as a secondary invader of other rots.
- All apple varieties are susceptible, but Bramley is especially susceptible with some infection in the core later in storage life.
- Other varieties with an open calyx are likely to be similarly affected. Penicillium expansum can grow slowly within fruit tissues without necessarily causing fruit to rot but still producing patulin as it does so.
In studies funded by the Food Standards Agency between 1998 and 2001 Penicillium expansum was detected widely within orchards, in soils, debris on the orchard floor on various parts of the apple tree including leaves, bark and fruit) and within the mature fruit core.
- This study could not establish any relationship between patulin levels in juice from processed fruit from the orchards studied and fungicide use.
- However in one case there may have been a possible connection between the use of dithianon during the blossom period in the spray programme compared with captan used in the orchard in the same period,.
- The dithianon use appeared to have some link to higher patulin levels.
- Since this work was carried out a number of new fungicides have become available to apple growers.
- One with particular activity against Penicillium is Bellis (boscalid + pyraclostrobin). Results from research in Belgium show a useful effect against Penicillium spp.
Control
Detailed guidance on control of storage diseases is provided elsewhere in this Best Practice Guide.
- Fungicides have been ineffective against P. expansum and most isolates are resistant to carbendazim so control or prevention has been entirely dependent on good hygiene, particularly of bins used for picking and storage – including those used for back storage after grading.
- These measures are still essential.
- Many of the approaches to general control of storage diseases will also help control both direct infection of apple by P. expansum and also limit secondary infection via damage caused by other storage diseases and physical damage to fruit from inappropriate handling and thereby minimize patulin in fruit.
- An application of captan at 2kg/ha plus boscalid + pyraclostrobin (Bellis) at 0.8kg/ha at petal fall has been shown to significantly reduce the incidence of storage rots.
- This is likely to be particularly useful with varieties that have an open calyx.
- The use of dithianon over the blossom period should be avoided if possible.
- Later season sprays for storage diseases may be required in some seasons depending upon rainfall.
- The use the of the storage rot risk assessment protocol will help guide planning harvest, storage and marketing.
- Monitor fruit by mineral analysis to determine storage potential.
- Do not use fruit that is at a high risk of storage rots or with poor mineral analysis for long term storage.
Harvesting
The harvesting period is a crucial part of the production process. Anything that can be done to minimise damage to fruit or reduce the incidence of other storage diseases will improve storability and marketable out turns as well as help to minimise patulin risk in any fruit sold for processing.
- Start the harvest as clean as possible by cleaning bulk bins before harvest to minimise carry-over of diseases to the new crops going into store.
- Careful supervision of picking will help to minimise bruising damage. It is important that all fruit with skin damaged or flesh exposed, as well as diseased fruit is rejected at the time of picking and left in the orchard.
- All soil contaminated fruit should also be rejected because it will have increased risk of rotting.
- Avoid getting leaves and pieces of branch in with fruit in bins.
- Avoid exposure of bins to rain as splash can be an important cause of disease spread.
- Significant bruising can occur to fruit in transport from orchard to store or packhouse.
- Make sure that tractor drivers are as aware as pickers of the critical points where fruit bruising can occur.
- When periods of rainfall occur during harvest it is essential to minimise mud contamination of fruit and equipment.
- Do not leave harvested fruit out in the orchard overnight, move it to a hard standing area to await loading into store.
- Fruit should be placed in cold store as soon as possible after harvest and ideally within 18 hours.
Post-harvest handling of apples
After harvest fruit should be handled in accordance with the guidance provided in the storage, packing and marketing section of this Best Practice Guide for UK Apple Production.
- Particular attention should be paid to temperature management of fruit with field heat being removed as quickly as possible.
- When fruit is removed from storage conditions and processed quickly patulin was rarely detected in the FSA project.
- However when fruit was deliberately left at ambient temperatures for 7 to 10 days out of store before processing, patulin levels increased.
- This finding confirmed previous reports about the need for rapid processing of fruit once it comes out of controlled storage conditions.
- Patulin levels can be more of a problem in fruit stored for longer periods and especially after three months in store.
- The FSA study also detected Penicillium expansum in the atmosphere of apple stores and packhouses and in the flotation water used in packhouse grading systems.
To reduce the risk of Penicillium .expansum and patulin it is important to clean down stores before the start of the apple season as well as cleaning the packhouse and grader regularly.
- In particular follow a programme of monitoring and changing flotation water regularly to avoid build up of problems.
- All rotten fruit, even those with only small rot lesions should be eliminated from consignments in the packhouse, even if the fruit is intended for processing.
- Supervision on the grading line is essential to keep damage to the fruit to a minimum.
- Routinely withdraw samples from the line to assess any damage that may be occurring from machinery or staff handling.
- Bruised fruit can quickly develop high patulin levels even if no mould growth can be seen.
- Regularly remove waste fruit from the packhouse and dispose of it well away from the packhouse and stores area.
- Wholesome fruit for juicing or other processing outlets should be kept in clean bulk bins and returned to store from the grader until despatch.
- The length of time fruit is in ambient temperatures should always be kept to a minimum (less than 12 hours).
- Fruit sent for processing should be pressed or processed as soon as possible and at the latest within 7 days of leaving the store.
- It is important to remember that fruit held at ambient temperature after withdrawal from cold store can develop high patulin levels very quickly.
It is the processors responsibility to ensure that their products comply with food regulations and do not exceed the statutory permitted levels of patulin.
- As suppliers to the processors, growers should need to make relatively few changes to their growing and handling operations to reduce the risk of patulin reaching high levels.
- This will help to ensure a successful processing outlet but any changes will also help the maintain the quality of fruit going to other outlets as well.
The Code of Practice for the Production of Apple Juice (June 2002) is available from:
British Soft Drinks Association
20-22 Stukeley Street,
London WC2B5LR
Tel: 020 74300356
Email: bsda@britishsoftdrinks.com
