# Probiotics in the Sourdough Bread Fermentation: Current Status
## 4 Probiotics and Postbiotics in Sourdough and the Impact on Human Health
The reduction of gluten content is important for people with gluten-related disorders. The long fermentation process of sourdough also helps break down gluten proteinsin wheat. Moreover, certain bacteria produce peptidases. Some _Lactobacillus_ strains, including _L. sanfranciscensis, L.rossiae, L. plantarum, L. brevis, L. pentosus, L. alimentarius, L. fermentum, L. paracasei, L. casei subsp. casei, and P. pentosaceus_ degrade gluten. Other gluten-degrading bacteria have been isolated form sourdough, such as _Bacillus_ spp. [140], and _Enterococcus mundtii_ and the yeast _Wickerhamomyces anomaly_ from locally fermented sourdoughs (Khamir) [60]. Gluten has baking properties, but its protein components, gliadin, and glutenins, could trigger undesirable immune responses, causing inflammation and damage [141]. Antioxidant and anti-inflammatory activities of peptides from cooked sourdough breads were described [142], where longer fermentation (72-96 h) increases the production of aromatic compounds with antioxidant activity [143]. LAB and yeast strains were isolated and molecularly identified from traditional Iranian sourdough. Based on total phenol production and antioxidant capacity assessments, all the identified traditional sourdough microorganisms significantly produced phenolic compounds. They showed significant antioxidant capacity improving bread's health benefits and quality [62]. EPS such as \(\beta\)-glucan, dextran, and inulin, are metabolites from LAB identified in sourdough fermentation. The \(\beta\)-glucan, for instance, is a prebiotic homopolysaccharide formed by glucose, presenting substantial health benefits, such as stabilized cholesterol levels, anti-inflammatory effects, and benefits for probiotic microorganisms [96]. The conclusions reached by [PERSON] et al. [117] provide significant insights into the general chemopre and prebiotic effects of LAB-generated sourdoughs and bread. In addition, exopolysaccharide are produced by LAB in sourdough, favoring great water retention. \(\beta\)-glucans also contribute to the viscoelastic properties of dough [96]. In the case of thermal treatment at 60 \({}^{\circ}\)C and 80 \({}^{\circ}\)C for up to 60 min, the molecular mass of the EPS was not significantly affected [144]. The glycemic index (GI) is the speed at which sugar enters our body's bloodstream and this parameter is affected by probiotics from sourdough. It is reported that sourdough bread has a lower GI than yeast bread. Bread with carbohydrates and starches, which are rapidly assimilated, increase the GI. An explanation of the decrease in the glycemic index is the higher level of lactic acid produced under these fermentation conditions. Lactic acid effectively diminishes postprandial glycemic and insulinemic responses, whereas acetic acid brings out a delayed gastric emptying rate. Moreover, the starch availability is reduced under baking heat, thus allowing the breakdown of sucrose to form EPS such as glucans which contribute to the rise in dietary fiber content [145; 146]. [PERSON] et al. [147] discussed that LAB could contribute to lowering the glycemic index by limiting the digestion rate of starch and converting glucose from digested starch into several bioproducts such as organic acids, fatty acids, sugar alcohols, bioactive peptides, and indigestible exopolysaccharides. Similar results were found by [PERSON] et al. [148], where the authors demonstrated results supporting the consumption of wheat and whole wheat bread produced by type 2 fermentation due to higher resistant starch and slowly digestible starch, and lower rapidly digestible starch and glycemic index values showing beneficial effects. However, some controversy exists in the literature. A systematic review selected 18 studies published up to June 2021 in the EMBASE, MEDLINE, Scopus, and Web of Science databases. The authors concluded that the consumption of sourdough bread has a lower influence on blood glucose compared to that of industrial bread or glucose [149].