The fundamental importance of maturation
The long maturation of a dough allows the LAB (lactobacilli of the sourdough), together with the proteases of the flour, to activate the enzymatic, chemical-physical processes responsible for the organoleptic qualities of the final product as well as its shelf life. The duration of the maturation process is essential, so the processes that it activates can fully carry out their activity.
The long maturations allow the LAB (lactobacilli of the sourdough), together with the proteases of the flour, to activate the process of hydrolysis of the gluten proteins and, therefore, also of the immunogenic fraction. This technique has already been used in the research to obtain the complete destruction of the toxic fraction (and, obviously, the total destruction of gluten network) and has been used to obtain a deglutinated flour. In current use, on the other hand, the sourdough contains an extremely variable pool of lactobacilli. The new method allows, therefore, for a specific flour with sourdough made with the same flour (or with the monococcus wheat flour as specified in the description of the new method), to obtain a dough with the longest possible maturation, with a gluten network suitable to be then used to have a valid final product according to the usual criteria (the so-called quality requirements or quality descriptors).
1. “The different micro-organisms used during fermentation have a complex metabolism that does not limit itself to making the mixture only macroscopic modifications linked to the use of sugars for the production of carbon dioxide (primary agent of leavening). In fact, these micro-organisms are endowed with enzymes capable of also substantially modifying the composition of the dough. In general, this action of the fermenting microbial flora is all the more evident the longer the leavening time is long and the more varied the type of microorganisms used. Therefore, rapid leavening obtained by means of brewer’s yeast has a mild action on the transformation of the various constituents of the dough and that, on the contrary, long fermentations obtained with acid pastes, containing various types of lactic bacteria and yeasts, cause very more pronounced in the different constituents of the dough. Recently several studies have been published to try to describe and summarize how the action of slow leavening obtained through acid pastes (therefore with methods closer to the traditional bread-making techniques) influence the organoleptic, nutritional and technological qualities of bread.” (Katina et al 2005, Corsetti and Settanini 2007).
2. “We have seen that long fermentations, obtained through the use of acid dough, improve the aroma and taste of the final product, thanks to the different organic acids produced by the activity of lactic bacteria on sugars. The long natural fermentations involve the release of a greater quantity of free amino acids in the mixture. This is due to the proteolytic activity of lactic bacteria and in part to the activation of proteases in the flour. It was found that the presence in the mixture of amino acids, allows the formation of compounds that contribute to the formation of the aroma of bread, thus improving its organoleptic qualities. The general increase in the aroma and palatability of the products obtained through natural fermentation makes the wholemeal breads more palatable which, as previously seen, often do not meet the favor of the consumers. The production of naturally leavened wholemeal bread could thus increase its consumption and encourage the intake of all the nutrients that this type of bread contains. Fermentation with sourdough compared to leavening with brewer’s yeast has different influences on the content of many of the bioactive compounds present in the bread. In general, the decrease in pH due to the use of acid paste causes an increase in the phenolic compounds and a decrease in compounds such as thiamine (vitamin B1), the dimers of ferulic acid (antioxidant) and phytic acid. The reduction of the phytic acid content is important because this molecule, binding to the minerals contained in the flour, makes them unavailable to the human body. A 62% phytic acid reduction with acid pastes has been described compared to a 38% reduction by leavening with brewer’s yeast (Lopez et al., 2001).
3. “NEW BREAD FROM ANTIQUE GRAINS Evolution of wheat varieties, milling and bread making techniques” (Research carried out with the scientific support of the Department of Agricultural and Food Production Sciences and the University of Florence and the technical collaboration of the Tuscan Coordination of Organic Producers).
3.1 “The most studied process for gluten degradation during bread making is sourdough fermentation. Sourdough is a mixture of flour and water that is fermented with LAB and yeasts (commonly Saccharomyces cerevisiae). The proteolytic activity of LAB enzymes to degrade gluten during dough mixing and fermentation may be attributed to the proteolytic activity of LAB and endogenous proteases of flour under acidic conditions”. This results in a weaker dough and a decrease in the loaf specific volume; these effects are accentuated when long fermentation times are used . In contrast to traditional sourdough processes, it has been reported that for total gluten degradation, long fermentation times are needed (approximately 24–72 h). The use of sourdough fermentation for bread making plays a crucial role in the development of sensory properties such as taste, aroma, texture, and overall quality of baked goods. This is due to the acidification, proteolysis, and activation of a number of enzymes [7,8].
3.2 “Different attempts have been made for reduction of immunogenic gluten sequences of wheat while keeping its baking technological properties. In the last decade, several studies have shown the capacity of proteolytic enzymes, mainly peptidases, to degrade gluten during food processing.”
4. “Another important effect of sourdough fermentation is to disrupt the gluten protein network. The highest molecular weight proteins in gluten are glutenins which are polymers stabilised by disulphide bonds. When glutenins are partially hydrolysed, the depolymerisation and solubilisation of the polymers occurs” (Thiele et al., 2004). “In addition, glutathione is an endogenous reducing agent in dough that can cleave disulphide bonds particularly when the pH is slightly acidic as during the first hours of sourdough fermentation” (Grosch and Wieaser, 1999; Wieser et al., 2008). “Furthermore, the activity of glutathione reductase is increased due to the effect of the lactobacilli on the redox potential” (Jänsch et al., 2007). “Finally, proline-rich polypeptides released by disruption of the gluten network, are exposed to the action of proline-specific peptidases from lactobacilli” (Trends in wheat technology and modification of gluten proteins for dietary treatment of coeliac disease patients. F Cabrera-Chávez, AM Calderón de la Barca Coordinación de Nutrición. Centro de Investigación en Alimentación y Desarrollo, A. C. Carretera a la Victoria Km 0.6 P. O. Box 1735. Hermosillo 83000, Mexico).
5. “More recently, it was shown that selected Lactobacillus in combination with fungal and/or malt proteases could decrease the residual concentration of gluten immunogenic sequences during extended fermentation times [2–5]. However, its utilization may affect the technological properties of dough and the quality of baked products” Here the study also shows that with a pool of selected LABs it is possible to arrive not only at the complete degradation of gluten but also at the elimination of toxic residues. (Microbial Proteases in Baked Goods: Modification of Gluten and Effects on Immunogenicity and Product Quality. Nina G. Heredia-Sandoval, Maribel Y. Valencia-Tapia, Ana M. Calderón de la Barca and Alma R. Islas-Rubio. Received: 1 May. 016; Accepted: 27 August 2016; Published: 30 August 2016).
6. “The degradation of gluten proteins influences the rheology of the doughs and, consequently, the structure of the bread (Thiele et al., 2004); moreover, the hydrolysis of the glutinic mesh improves the workability of the dough (Wehrle et al., 1999). Amino acids and small peptides released during fermentation are important for microbial growth as well as for the development of aroma in bakery products. The proteolytic/peptidolytic activity of lactic bacteria can contribute to the hydrolysis of bitter peptides and the release of bioactive peptides (Mugula et al., 2003). Lactic bacteria play a substantial role in proteolysis during fermentation” (Di Cagno et al., 2002; Wehrle et al., 1999).
7. “The most studied process for gluten degradation during bread making is sourdough fermentation. Sourdough is a mixture of flour and water that is fermented with LAB and yeasts (commonly Saccharomyces cerevisiae). The proteolytic activity of LAB enzymes to degrade gluten during dough mixing and fermentation may be attributed to the proteolytic activity of LAB and endogenous proteases of flour under acidic conditions. This results in a weaker dough and a decrease in the loaf specific volume; these effects are accentuated when long fermentation times are used. pag. 7.” (Microbial Proteases in Baked Goods: Modification of Gluten and Effects on Immunogenicity and Product Quality. Nina G. Heredia-Sandoval, Maribel Y. Valencia-Tapia, Ana M. Calderón de la Barca and Alma R. Islas-Rubio. Received: 1 May 2016; Accepted: 27 August 2016; Published: 30 August 2016).
8. For those with a less severe reaction, with what Pollan calls “gluten intolerance”, which is more commonly known as non-celiac gluten sensitivity, the sourdough process may increase tolerance for consuming the bread, says Alessio Fasano, director of the Center for Celiac Research at Massachusetts General Hospital. The long fermentation process to make sourdough bread the old fashioned way does reduce some of the toxic parts of gluten for those that react to it, says Peter Green, director of the Celiac Disease Center at Columbia University. (Https://www.theguardian.com/lifeandstyle/2016/mar/23/sourdough-bread-gluten-intolerance-food-health-celiac-disease).
9. Sourdough and degradation of protein: A grounded guide to gluten: How modern genotypes and processing impact wheat sensitivity – Chapter fermentation and microbial enzymes – (Lisa Kissing Kucek – Lynn D. Veenstra, Plaimein Amnuaycheewa and Mark E. Sorrels – Comprehensive reviews in food schience and food safety Vol 14 – 2015).
10. An important contribution of sourdough fermentation is wheat endoprotease activity that require a low pH level (Hartmann et al. 2006 – Ganzle et al. 2008 – Loponen et al. 2009).