The power of sour - A review: Old traditions, new opportunities

Currently, there is a strong interest in sour beers, with more breweries producing sour styles and sales continuing to increase. There are many different ways for producing sour beer, offering breweries a variety of opportunities to pursue new beverages and diversify their portfolio. These methods range from modern kettle souring and short term mixed fermentation to traditional long term mixed fermentation and maturation in wooden barrels. While the first methods enable quick souring, these beers generally lack the flavour complexity that can be obtained through more traditional methods. Here, we discuss the microbiology of sour beers and review the most common production methods as well as the most important beer styles that are produced using these methods. Further, we report a number of novel methods that have the potential to produce the next generation of flavour-rich sour beers. Increased knowledge on the microbiology and flavour development in traditional sours will help developing such next generation of sour beers.