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Gluten

Wheat, barley, rye, and derivatives

Malt, malt vinegar, malt extract
Barley contains gluten; all malt-derived ingredients therefore contain gluten unless explicitly labeled gluten-free.
Modified food starch
Could be wheat-derived. US labels must disclose wheat starch, but cross-contamination and processing inconsistencies occur.
"Starch" (without a source qualifier)
Wheat starch is a real ingredient and "starch" doesn't have to disclose it on all jurisdictions.
"Natural flavors" and "natural flavor"
Wheat-derived flavoring components are possible.