# Functional and Healthy Features of Conventional and Non-Conventional Soundoughs
## 7 Sourdough Effectiveness on Rheology, Shelf-Life and Safety  
The impact of sourdough on properties and rheological behavior of dough has been widely investigated. Generally, changes may be attributed to several intrinsically related factors, including variations in the rate or amount of acid produced [100]. For instance, a low proteolytic degradation of wheat proteins affects the physical properties of gluten and, thus, influences the firmness and staling of the final baked product [101]. The specific proteolytic activity of sourdough microorganisms also has a great impact [102]. As proved by [PERSON] et al. [103], the use of sourdough, prepared either from a single strain or a mixed strain starter culture, significantly influenced the rheological properties of wheat flour dough; sourdough prepared with starter cultures increased the softening level of the dough. Regarding gas production in sourdoughs, [PERSON] and [PERSON] [27] proved that the contribution of yeasts and LAB changes according to the type of starter and the dough technology. This aspect is particularly important in the GF products where the lack of the viscoelastic gluten system is responsible for low expansion and gas retention during leavening [104]. The efficiency of the addition of sourdough on GF bread quality was demonstrated in various formulations made of a different kind of flour by [PERSON] \begin{table}
\begin{tabular}{c c c c} \hline
**LAB Strains** & **Compounds with Antifungal Activity** & **Fungal Target Tested** & **Reference** \\ \hline _L. sanfranciensciens_ CB1 & Acetic, caproic, formic, propionic, butyric and n-valeric acids & _Fusarium graminearum_ 623 & [91] \\ \hline _L. plantarum_ 21B & \begin{tabular}{c} Phenymllactic acid and \\ 4-hydroxyphenyllactic acid \\ \end{tabular} & _Apergillus niger_ FTDC3227 & [92] \\ \hline _L. plantarum_ CRL 778 & & & \\ _L. reuteri_ CRL 1100 & & & \\ _L. brevis_ CRL 772 & & & \\ _L. brevis_ CRL 796 & & & \\ _L. buchneri_ FUA 3525 & & & \\ _L. diolovorans_ DSM 14421 & & & \\ _L. rossiae_ LD108, & & & \\ _L. parlamientarius_ PB127 & & & \\ \hline _L. amylocorus_ DSM 19280 & \begin{tabular}{c} Lactic acid, acetic acid, \\ 3-phenylpropanoic acid, p-cumaric, \\ (E)-2-methylcinnamic acid, 3-phenyllactic \\ acid and cyclic dipeptides \\ \end{tabular} & \
\begin{tabular}{c} _Fusarium calumorum_ FST 4.05 \\ _Asppergillus niger_ FST4.21 \\ _Penicillium expansum_ FST 4.22 \\ _Penicillium roqueforti_ FST 4.11 \\ \end{tabular} & [96, 97] \\ \hline _L. paracasei_ subsp. _tolerans_ L17 & Cell-wall binding and enzyme-mediated degradation &
\begin{tabular}{c} _Fusarium proliferation_ FST 5991 \\ _Fusarium proliferation_ FST 5689 \\ _Fusarium graminearum_ R 4053 \\ \end{tabular} & [98, 99] \\ \hline \end{tabular}
\end{table} 
Table 1: Some lactic acid bacteria strains from sourdoughs tested for their antifungal activity. et al. [105], which used a Type I GF-sourdough with a stable association between \(L\). _santrancisensis_ and _C. humilis_. The positive effects of sourdough on rheology and texture, in terms of volume and softness, led to an extended shelf-life of the baked products. This aspect is certainly of great interest for the bakery industry which has recently reevaluated the traditional sourdough fermentation to contrast the short shelf-life of baked products, like bread, mainly caused by spoilage microorganisms. In fact, sourdough can act as a natural preservative able to replace the use of chemical preservatives. Above the antifungal activity described in the previous section, antibacterial activity has been also scientifically proven [106]. Bread quality and safety can be affected by spore-forming bacteria, such as _Bacillus subtilis_, which mainly occur on the outer parts of grains, and consequently can contaminate also the other ingredients and/or bakery environment [107; 108].