Orange peel is added to beers for flavor and its aromatic qualities, generally in the last few minutes of wort boiling and should be strained out before bottling. Some brewers add coriander and some other flavoring to the primary fermentation vessel to get a stronger flavor.
Bitter Orange peel is thick, rough, and generally is green, yellow, or gray colors. The flesh of the orange is dry and very bitter. The peel, which is used in brewing beer is less bitter, has a mild orange flavor. Bitter orange gives beers a citrusy and herbal flavor and aroma. Is used to flavor Belgian white ales to give them a citrus & herbal notes
Sweet orange peel has a brighter orange color and has a relatively thin peel compared to bitter orange and when added in similar quantities to bitter orange peel, it gives a beers a strong orange flavor. Sweet orange peel is combined with coriander in some Belgium beers, used in holiday ales, and as an aromatic ingredient in some wines.