Which ingredient found in baking powders is often non-kosher?

The ingredient often found in baking powders that can be non-kosher is cream of tartar. Cream of tartar is a byproduct of wine production and can sometimes be processed or mixed with other substances that do not meet kosher standards. The source of the cream of tartar is particularly important in determining its kosher status, as it can be derived from grapes, and the kosher status of the grapes and the winemaking process can affect the final product.

While baking soda, flour, and sugar are generally derived from plant sources that are typically considered kosher, cream of tartar is unique in that its production process is closely tied to the wine industry, where kosher adherence is crucial. Thus, cream of tartar is the ingredient within baking powder that warrants special attention regarding its kosher status.