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Traditional Monier-Williams methods, commonly used for sulphite analysis, may produce elevated SO₂ results when applied to dehydrated Allium products. During the analytical procedure, naturally occurring sulphur compounds can be converted into sulphur dioxide, even when no sulphites have been added.

 

To address this challenge, the spice industry developed ASTA Method 30.0, a modified Monier-Williams method specifically designed for dried garlic and dried onion. The method minimises Allium-specific interferences and provides a more reliable determination of added sulphites.

 

This distinction is particularly important for the European market. Under Regulation (EU) No. 1169/2011, sulphur dioxide and sulphites must be declared as allergens when present in the final food at levels exceeding 10 mg/kg (or 10 mg/L), expressed as SO₂. As different analytical methods may produce different results for the same sample, the choice of test method can have a direct impact on product acceptance and labelling decisions.

 

For this reason, the analytical method should always be agreed before shipment and clearly specified in the sales contract or product specification.

 

Van der Does Spice Brokers recommends ASTA Method 30.0 as the contractual reference method for sulphur dioxide determination in dried garlic and dried onion. The method was specifically developed for dehydrated Allium products and is widely used within the international garlic industry, including by major producers in China. Defining the analytical method in advance helps prevent unnecessary disputes, promotes consistent interpretation of laboratory results and supports transparent international trade.