Which alcohols may have restrictions due to kosher concerns?

Blended bourbons and scotch may have restrictions due to kosher concerns primarily because the kosher dietary laws are very stringent regarding the ingredients and production processes of alcoholic beverages. Bourbon, particularly when blended, may use flavorings or agents that are not certified kosher, which can create issues regarding its consumption by those adhering to kosher standards.

For scotch, the maturation process often involves barrels that may have previously held non-kosher products, including certain wines or spirits, which could potentially impart non-kosher elements to the scotch. Furthermore, both blended bourbons and scotch are sometimes produced using a mixture of grains or additives that are not certified kosher.

In contrast, while other spirits like whiskey, rum, tequila, or gin can also have kosher considerations, they tend to be more straightforward in their ingredients and production methods, making it less common for these alcohols to have widespread restrictions as seen specifically with blended bourbons and scotch.