California dominates global walnut production, yet the US also imports walnuts — particularly in-shell and shelled dried forms — subject to FDA oversight for aflatoxin and other mycotoxin contamination at entry. Classification hinges on whether the product is in-shell or shelled and fresh versus dried, distinctions that affect both duty treatment and storage and labeling requirements. Importers should note that walnut shipments may be detained for sampling if prior lots from the same shipper have triggered FDA alerts. Moisture content and grade specifications are critical commercial variables when sourcing for retail, ingredient, or food-service channels.

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