The age-old practice of food fermentation is enjoying a well-earned renaissance. As knowledge around the importance of our gut microbiota has grown, so too has the evidence that fermented foods can help support a healthy gastrointestinal tract, boost the immune system and even improve mood. This is due to both the probiotic microbes they contain, and the enhanced nutritional value of fermented foods themselves. In this comprehensive guide, fermentation specialist Caroline Gilmartin delves into the processes and mechanisms involved in both wild and cultured fermentation, examining the microbes involved, parameters for optimal fermentation and what happens if you alter them. Topics covered include the importance of the microbiota; gut health; milk and water kefir; yoghurt; kombucha; vegetable fermentations; appetising recipes; suggested flavour combinations and finally, safety measures and troubleshooting. AUTHOR: Dr Caroline Gilmartin is a fermentation specialist with a background in microbial genetics. Her Bristol-based company, Every Good Thing, makes kefir and kimchi for local shops, as well as running workshops that teach the basics of maintaining gut health and sustainable techniques for fermentation. 186 colour photographs