# Functional and Healthy Features of Conventional and Non-Conventional Soundoughs
## 3 Nutritional and Functional Features of Sourdough  
Sourdough fermentation is certainly the most conventional and efficient tool for guaranteeing rheology, sensory, hygiene and shelf-life features [14]. Additionally, it has the potentiality to enhance the nutritional and functional features of wheat flours [35; 36; 37; 38]. The positive effects provided by sourdough technology can be summarized as:  
* preservation of food through acetic acid, lactic acid, alcoholic, and alkaline fermentations;
* food enrichment with compounds that originate either from biochemical reactions (e.g., essential amino acids, proteins and essential fatty acids), or biosynthesis (e.g., vitamins);
* development of aromas, flavors and textures in food substrates;
* detoxification during food fermentation processing. Moreover, it has been reported that sourdough fermentation can lower glycemic index, increase mineral bioavailability, reduce gluten content and reduce starch digestibility, mainly through the organic acids production and other complementary mechanisms [12; 39]. The main outcomes of sourdough fermentation are shown in Figure 2.  
In recent years the development of high-quality gluten-free (GF) products has become an important socio-economic issue and a new approach in this framework is represented by the application of sourdough fermentation [40]. Common products for celiacs available on the market are often characterized by poor palatability and lack of minerals and fibers [41]. Moreover, they usually have a low amount of health promoting nutrients, such as B vitamins groups, which are essential in the human diet; for instance, folate (B11) is involved in fundamental metabolic reaction, biosynthesis of nucleotides, building blocks of DNA and RNA and prevent neural tube defects in newborns [40]. Consequently, fermentation with LAB and yeasts can be considered an effective methodology in food production suitable for the development of new kinds of GF products with nutraceutical and health-promoting features [42]. Applying microbial selected cultures to suitable raw materials, the fermentation process can be modulated, also  
Figure 1: Schematic description of the three main types of sourdough. enhancing the content of bioactive metabolites and other compounds, such as glutathione, which exert an antioxidant activity [22; 43; 44; 45]. Moreover, the sourdough fermentation can be useful in preserving some good sensory characteristics, such as products' structure and/or softness maintenance during storage, which are usually compromised by the lack of gluten [46; 47]. Therefore, the selection of specific sourdough cultures has been considered as a new tool for GF food processing [14; 48; 49]. Various ecological studies have provided useful information on the presence of competitive LAB and yeasts strains, which can be used as candidates for starter development [50]. In rice, maize, teff, and amaranth sourdough, for instance, is frequently used to isolate microorganisms such as: _L. fermentum, L. plantarum_, and _L. paralimentarius_[51]. Above them, strains of _L. helveticus, L. pontis_, and _S. cerevisiae_ are most competitive in different kind of cereals, pseudo-cereals, and cassava sourdoughs [10; 52]. Positive cooking performance, obtained with the use of sourdough in GF products, in terms of definite volume, flavor, texture and mouthfeel encourages further studies and the development of an industrial production [40]. In particular, the flavor profile of the product can be greatly affected by the use of sourdough, depending on type of starter cultures, fermentation conditions, baking conditions and raw material. Recently, researchers have proposed the use of sourdough-fermented ingredients to reach new sensorial profile and enhance nutritional value in pasta [13]. The use of sourdough for pasta fortification has been explored under several aspects and has also been applied with success to mixed flour composed by pseudo-cereals and legumes, allowing an increasing of \(\gamma\)-aminobutyric acid (GABA) levels [53].