Production And Conservation Of Starter Cultures: From "Backslopping" To Controlled Fermentations

As human society has evolved from small, nomadic groups of hunter-gatherers to large, stationary civilizations, there has been an increased reliance on the preservation of foods to sustain populations through periods of reduced agricultural productivity. Microbial fermentations have been used for millennia to preserve high water activity foods such as fruits, vegetables, and meats. Originally, a process called "backslopping", in which a small portion of a previously successful fermentation is used to inoculate fresh substrate was used to generate starter cultures for future fermentations. However, these processes fell from favor in the nineteenth century concurrently with the rise in public interest and governmental regulations concerning food safety. Starter cultures for mass-produced fermented foods were subsequently required to be produced from defined GRAS microorganisms, triggering a systematic reduction of microbial diversity seeding the digestive tract. Recently, several landmark studies have highlighted the importance of a healthy gut microbiome leading to a renewed interest in more traditional (artisanal) methods of food fermentations. New methods of mixed-strain starter culture production, particularly immobilized cell reactors, present attractive alternatives to the more traditional batch reactors due to their ability to produce a more robust and diverse starter all in one step. Additionally, advances in culture preservation technology, like freeze- and spray-drying, have increased the long-term viability and reduced the cost of starter cultures.