Residues on nectarines
From the October 2008 edition of Agriculture Today.
Check list
Fruit growers can make the following checks to prevent possible DPA residues on non target crops:
- Triple rinse all dip tanks and packing and grading equipment following pome fruit harvest
- Store wooden packing bins in direct sunlight to help evaporate any absorbed dip solution
- Know the use pattern of borrowed bins
- Use plastic packing bins
- Follow all directions on the label and Material Safety Data Sheets (MSDS) on DPA
- Test fruit for chemical residues as part of a quality assurance program
Effective monitoring by horticulturists has identified the cause of illegal chemical residue on nectarines.
The chemical diphenylamine (DPA), widely used on apples and pears as a postharvest dip to prevent superficial scald on fruit, was found for the first time on nectarines during routine monitoring.
NSW Department of Primary Industries (DPI) horticulturist, Lawrence Ullio, said there was no implication of deliberate wrongdoing and growers were happy to receive help to correct the problem.
“Diphenylamine is not registered for use on stone fruit and the Pesticide Act (1999) makes its presence on stone fruit illegal,” Mr Ullio said.
“We identified causes of contamination after trace back, and interviews with horticulturists, fruit wholesalers, packing houses and fruit growers on the central and southern tablelands and slopes.”
The detection was part of the three year Cleanfresh pesticide residue monitoring project, conducted by NSW DPI.
DPA is only registered for use on apples and pears and helps protect against scald, a physiological disorder that can cause brown irregular patches on the skin of fruit during long-term cold storage.
According to the NSW Food Authority, DPA levels on all samples were well within the dietary intake guidelines, and posed no health risk to consumers.
All residue violations on nectarines came from packing houses handling both pome and stone fruit.
Mr Ullio says contamination can occur when fruit growers and packing houses conduct postharvest operations on different fruit lines using same equipment.
“Residues of DPA may still be present in dip tanks, packing and grading equipment and this could result in cross contamination,” he said.
Softwood bins are another possible site for contamination.
They are widely used for harvesting fruit and can absorb DPA when submersed in dip tanks.
Over a season, DPA absorbed in these bins could be significant.
Wooden bins are also used to store apples or pears dipped in DPA in cool rooms during winter and reused in spring to harvest stone fruit.
This may also contaminate harvested fruit.
Contact Lawrence Ullio, Sydney Markets, (02) 9735 9605, 0412 436 871.
