Flavoring
Added flavor whose solvent is often alcohol, and whose base can be animal-derived.
Why this is a critical point
Flavorings — natural or synthetic — are often dissolved in ethanol for stability, and some meat, cheese, or butter flavors use an animal-derived extract base. "Natural flavor" on a label does not automatically mean halal, since it may contain pork derivatives or a significant amount of alcohol.
Halal alternative
Halal-certified flavoring with a non-ethanol, plant- or microbial-based solvent and base.