Sulphur Dioxide (SO2) Ratios and Limits in Dried Apricot

The sulphuring (Sulphur Dioxide - SO2) process, traditionally applied to extend the shelf life of dried apricot, preserve its natural colour (orange/yellow) and prevent microbial spoilage, is the most important parameter of food safety and export standards. Especially in international B2B trade, full compliance with the buyer country’s legal limits carries critical importance at customs crossings.

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Legal SO2 (Sulphur Dioxide) Limits by Country

The maximum sulphur amount (ppm - milligrams per million parts) that countries permit in dried apricot imports varies from country to country, and the buyer country’s food regulations can be updated over time. For this reason, instead of working from a fixed figure, it is essential for export safety to confirm the applicable SO2 limit before each shipment according to that country’s current regulations.

No Limit Applies to Natural Sun-Dried Products: unsulphured natural dried apricots (sun-dried apricot) are dried by darkening in the sun and no sulphuring process is applied; for this reason, no SO2 residue limit is relevant for this product group.

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Factors Affecting the Sulphur Ratio and Its Control

1. Fumigation Time: the duration (typically 10-18 hours, varying by lot and season) that the apricot, once harvested fresh, is exposed to pure sulphur smoke burned in the fumigation chamber (sulphur room) directly determines the final ppm level.
2. Degree of Drying: as the sun-drying period lengthens, the moisture content in the fruit drops while the sulphur gas also escapes into the air and decreases.
3. Storage Temperature: hot storage conditions cause the sulphur to dissipate faster and the fruit to darken. For this reason, ideal storage should be carried out in cold storage facilities.

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Reliable Analysis Processes Before Export

In export shipments, requested analyses are carried out at independent laboratories and confirmed on a lot basis. The following standard methods are used in the analyses performed:

• Monier-Williams Method: the acid-base titration method officially recognised in food codexes and most widely used for determining sulphur dioxide.
• Moisture Determination: export standards require the moisture content to be kept at a controlled and balanced level; this balance also directly supports sulphur stability.