Fruit beers, beers with or without a co-fermentation step with fruits.

Belgium is known for its traditional lambic beer productions, obtained through spontaneous fermentation and maturation in wooden barrels. Lambic beer is also used to make fruit lambic beers, such as Kriek beer. Despite fruit beer being an old beer type, dating back to the second half of the seventeenth century, no research has been performed on lambic beer-fruit co-fermentation processes. Further, these beers get competition from market-driven, sweet, (fruit-)flavored ones without the co-fermentation step. This paper will first discuss a new, general fruit beer classification, going from sour fruit beers produced through co-fermentation to sweet ones without a co-fermentation step. Second, a state-of-the-art of the scarce literature on the microbiology and metabolomics of lambic beer-fruit co-fermentation processes will be given.