Fermented Beverages Revisited: From Terroir to Customized Functional Products

The production of fermented beverages dates back to antiquity. The substrates most frequently employed are milk, fruits and cereals, resulting in a wide range of products, some of which are currently recognized as characteristic of certain geographical areas. The early studies on fermented beverages aimed to document the production procedures and characterize the driving microbiota. As data accumulated and the need for standardization became more evident, assessment of the metabolic activities associated with the quality characteristics of each product towards the selection of the most suitable starter cultures dominated research. At the same time, the beneficial attributes for human health were also recorded, highlighting the importance of the thorough characterization of the factors that determine these activities. Nowadays, a wealth of knowledge has accumulated, which, combined with the conceptual, methodological and technological advances of recent years, enable us to study the factors that affect the development of these microbial communities, elucidate the mechanisms by which their metabolic activities direct the fate of bioactive compounds and unravel how the latter modulate human health.

In recent years, research in the field of fermented beverages has been concentrated mainly in the following four areas: 1. physicochemical and microbiological characterization, 2. the effect of climate change and mitigation strategies, 3. quality improvement and 4. the development of new products.

Our knowledge regarding the microbial communities that drive spontaneous fermentations, their dynamics during fermentation and the storage of the final products, as well as their metabolic activities and how their metabolites shape the physicochemical properties and the nutritional value of fermented beverages, has been significantly improved over the recent years. This improvement has been facilitated by the technological advances that enabled the rapid characterization of microbial communities to the species level, along with their functional metabolic pathways. Thus, a series of studies have improved our understanding of already established fermented beverages, such as kombucha [1,2], and they have introduced traditional products, such as the Peruvian “Chicha de siete semillas” [3], and ethnic practices, such as the epop of India [4].

The effects of climate change on fermented beverages, along with possible mitigation strategies, have drawn scientific attention, particularly in viticulture. Global warming accelerates the ripening of grapes but alters their composition; they contain more sugars and fewer organic acids. From a cultivation point of view, several agricultural practices have been proposed to address this issue [5]. From a winemaking perspective, the greater carbohydrate content could lead to higher ethanol production, which is not always perceived positively by consumers, and the lower acidity would be detrimental to the stability of the product. Collectively, these changes would result in a significant deviation from the typical characteristics of wine. Among the possible mitigation strategies, biological acidification by suitable non-Saccharomyces yeast strains that would utilize carbohydrates to produce lactic acid instead of ethanol seems to be a realistic solution. Their application in a wide range of grape varieties, along with the effect on the physicochemical characteristics and the sensorial profile of wine, has been extensively assessed, highlighting the feasibility of this approach.

The term “quality” may refer to a wide range of properties that may be affected by a series of biotic and abiotic factors, such as the type and characteristics of the raw materials employed, the metabolic capacity of the microorganisms driving the fermentation, the conditions of fermentation etc. Not all fermented beverages have the factors affecting their quality features fully elucidated. Therefore, the recent advances in the field of metagenomic analyses, coupled with analytical tools that enable the integration of metagenomic with metabolomic approaches, have improved our understanding of the factors that affect the fermentation process; the role of the different members of the microcommunity and how they direct the quality of the final product, such as in the case of green kombucha [6] and Huangjiu fermentation [7]. The fate of bioactive compounds has also been the epicenter of intensive study. Thus, the factors that affect the concentration of compounds, such as phenolics, amino acids, peptides and fatty acids, during fermentation, as well as their biological activities, have been extensively assessed. Especially regarding the latter, a wealth of data has been generated through in vitro experiments, indicating significant biological activity that leads to specific health claims [8]; in many cases, these are accompanied by adequately described modes of action. As a result, there is a constant effort to enhance the nutritional value and the functional activities of fermented beverages, mostly through the use of carefully selected starter cultures [9] or the direct addition of specific nutrients [10].

Finally, the development of new products with customized functional potential has also been a field of intensive effort. Research has mostly focused on the customization of kefir and kombucha beverages, either by using alternative raw materials or by using microbial strains with specific metabolic activities. These have led to the development of a wide range of kefir and kombucha analogs [8], many of which hold very promising capacities. In addition, many fermented beverages with interesting properties have also been developed by using non-conventional materials or underexploited strategies [11,12].

The aim of this Special Issue was to contribute to the aforementioned research areas with studies of high quality. This has been achieved, as very interesting manuscripts, addressing research gaps and providing new insights, have been published. These manuscripts improve our understanding of fermented beverages and form a basis for future research.