Effects of sourdough on bread properties (sensory and nutritional qualities and product shelf-life)

Sourdough is a potential option to improve bread quality also in wheat baking due to the natural, additive-free image of products containing sourdough. Furthermore, recent results demonstrate the effectiveness of sourdough fermentation in improving the nutritional value of cereal products. During cereal fermentation, typically up to 24 h at moderate temperatures, the metabolic activity of the microorganisms present is in interaction with the grain constituents. Sourdough fermentation can influence the nutritional quality by decreasing or increasing levels of compounds, and enhancing or retarding the bioavailability of nutrients (Poutanen et al., 2009). Sourdough is a mixture of flour and water fermented with lactic acid bacteria (LAB) and yeasts, which determine its characteristics in terms of acid production, aroma and leavening (Katina et al., 2006). A slack flour dough is inoculated with microbial starter, “mother culture”, which is constantly renewed in a cyclical way, using specified recipes and ripening conditions. As a consequence, sourdough is a unique food ecosystem: it selects for LAB and yeasts which are adapted to the environment, and hosts highly specific microbial communities (De Vuyst and Vancanneyt, 2007). When used in optimised proportions, sourdough can improve volume, texture, flavour, nutritional value of bread and increase the shelf life by retarding the staling process and by protecting bread from mould and bacterial spoilage (De Vuyst and Vancanneyt, 2007).The changes in cereal matrix potentially leading to improved nutritional quality are numerous. They include acid production, suggested to retard starch digestibility, and to adjust pH to a range which support the action of certain endogenous enzymes, thus changing the bioavailability pattern of minerals and potentially protective compounds in the blood circulation (Katina et al. 2005). The action of enzymes during fermentation also causes hydrolysis and solubilisation of grain macromolecules, such as proteins (i.e.: gluten) and cell wall polysaccharides. It has also been suggested that degradation of gluten may render bread better suitable for celiac persons (Poutanen et al., 2009; Di Cagno et al., 2004). Some of the mechanisms to improve and enhance the nutritional effects of fermented cereal systems are dependent on adjustment of the acidity for optimal action of the enzyme system present. Other mechanisms may be directly linked to other metabolites produced by yeast and lactic acid bacteria, and then the control of different metabolic routes in the fermenting organisms becomes a key issue. (Poutanen et al., 2009; Venturi et al., 2013). Among the typical Tuscan products one of the most popular is the famous Tuscan bread, a sour dough bread baked in a wood. With the aim to safeguard ‘real’ Tuscan bread and its heritage, some chemical and sensory parameters and/or indexes starting from the results of the analysis of samples of the artisan bakers belonging to “Consorzio Promozione e Tutela del Pane Toscano” were selected to differentiate sour dough Tuscan bread from industrial fresh products. References De Vuyst L., e Vancanneyt, M. (2007) Biodiversity and identification of sourdough lactic acid bacteria. Food Microbiology 24, pp. 120-127. Di Cagno R., De Angelis M., Auricchio S., Greco L., Clarke C., De Vincenzi M., Giovannini C., D’Archivio M., Landolfo F., ParrilliG., Minervini F., Arendt E. Gobbetti M. (2004) Sourdough bread made from wheat and non toxic floursand started with selected lactobacilli is tollerate in celiac sprue patiens. Applied and environmental microbiology 70, 1088-1096 Katina K., (2005) Sourdough: a tool for the improved flavour, texture and shelf-life of wheat bread. Espoo. VTT Publications 569. 92 p. + 81 p. Katina K., Heinio R. L., Autio K., e Poutanen K. (2006) Optimization of sourdough process for improved sensory profile and texture of wheat bread. LWT - Food Science and Technology 39, pp. 1189-1202. Poutanen K., Flander L., Katina K. (2009) Sourdough and cereal fermentation in a nutritional prespective. Food Microbiology, 26, pp 693-699 Venturi F., Andrich G., Sanmartin C. and Zinnai A. (2013) The Kinetics of Fermentations in Sourdough Bread Stored at Different Temperature and Influence on Bread Quality. Journal of Bioprocessing and Biotechniques, vol. 3(3), 134 http://dx.doi.org/10.4172/2155-9821.1000134