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Surdough fermentation (IV part)

by luciano

Rheology of the sourdough: Influence of LAB action


“Effects of LAB to dough structure

The structural effects of sourdough in wheat-based system may first be due to the direct influence of low pH on structure-forming dough components, such as gluten, starch, arabinoxylan etc. (Angioloni et. al., 2006). Dough is very sensitive to changes in ionic strength and pH and such changes could have direct impact on the constituents of dough (Clarke et al., 2002). The drop in pH value caused by the produced organic acids influences the viscoelastic behaviour of dough. A correct description of the changes in dough behaviour is necessary to maintain handling and machinability in industrialized production (Wehrle et. al., 1997). A number of earlier studies have examined influence of acids and different pH values on the dough properties. All of these confirmed that changes in the absolute pH value of sourdough significantly influence sourdough components.

The pH profile may affect the time frame during which the acid influences the constituent ingredients of the dough. The changing pH values during sourdough fermentation period may also afford passage through a range of pH values close to the optimum for various enzymes present in the dough system. It is so-called secondary (indirect) effect of sourdough acidification (Clarke et al., 2004). The activity of proteolytic and amylolytic enzyme present may be influenced to a greater degree by the pH profile of the biological acidification fermentation period in contrast to the rather instantaneous nature of the chemically acidified regime. Optimum activity of these enzymes, which play significant role in changes of dough constituents, achieve optimum activity at pH 4-5 for the proteolytic and pH 3.6 – 6.2 for the amylolytic enzymes (Belitz & Grosh, 1992). Other enzymes that might affect the structural components of the dough the activity of which is pH dependent include peroxidases, catalases, lipoxigenases and polyphenol oxydases (Belitz & Grosh, 1992; Clarke et. al., 2002). Results obtained by the the fundamental rheological tests, baking tests, and farinograms show that activity of some enzymes in the biologically acidified dough led to structural changes in the dough (Corsetti et. al., 2000; Clarke et. al., 2002; Clarke et. al., 2004). Corsetti et. al. (2000) also reported that even limited photolytic degradation of wheat proteins affects the physical properties of gluten, which in turn can have a major effect on bread firmness and staling.

Surdough fermentation (III part)

by luciano

Carbohydrate metabolism
“The ratio between lactic and acetic acid is an important factor that might affect the aroma profile and structure of final product. Acetic acid, produced by heterofermentative LAB, is responsible for a shorter and harder gluten, while lactic acid can gradually account for a more elastic gluten structure (Lorenz, 1983; Corsetti & Settani, 2007).
Influence of Acidification on Dough Rheological Properties Daliborka Koceva Komleni, Vedran Slaanac and Marko Jukić Faculty of Food Technology, Josip Juraj Strossmayer University of Osijek, Croatia 2012- www.intchopen. )”

Metabolism of proteins
“According to the results of studies performed by Gerez et. al. (2006) 13 nine lactobacilli and four pediococci were able to use gluten as a nitrogen source. Gerez et. al. (2006) also reported an increase in essential amino acids (treonine, valine, lysine and phenylalanine) in a gluten based medium fermented by LAB strains.
Subsantial hydrolysis of gliadinin and glutenin proteins occurs during sourdough fermentation. Proteolityc activity in sourdough originates not only from LAB enzymes, than derives also from the cereal materials present in sourdough (Thiele, 2002; Thiele, 2004). Except activity of own enzymes, LAB contribute to overall proteolysis during sourdough fermentation by creating optimum (acidic) conditions for activity of cereal proteinases (Vermeulen et al. 2006). The partial hydrolysis of glutenins during sourdough fermentation results in depolymerisation and solubilisation of the gluten macro peptide (GMP). After 24 hours of fermentation with defined lactobacill strains, all gluten proteins were SDS-soluble (Thiele et. al., 2003). Glutathione (GSH) is the most relevant reducing agent in wheat doughs (Grosh & Wieser, 1999). Heterofermentative lactobacilli express glutathione reductase during growth in dough and reduce extracellular oxidized glutathione (GSSG) (Jänsch et. al., 2007). The continuous transformation of GSSG to GSH by LAB metabolism maintains high SH levels in wheat doughs, and increase the amount of SH-groups in gluten proteins (Vermeulen et. al., 2006)
The level of individual amino acids in wheat dough depends on the pH level of dough, fermentation time and the consumption of amino acids by the fermentative microflora (Thiele et. al., 2002). In wheat sourdoughs, Lb. brevis linderi, Lb safransciensis, Lb. brevis and Lb. plantarum have been reported to increase the levels of aliphatic, dicarboxylic and hydroxyl amino acids (Gobbetti et. al., 1994a, Gobbetti et. al., 1994b). The yeasts, S. cerevisiae and S. exiguous decrease the total level of amino acids. Influence of Acidification on Dough Rheological Properties Daliborka Koceva Komleni, Vedran Slaanac and Marko Jukić Faculty of Food Technology, Josip Juraj Strossmayer University of Osijek, Croatia 2012- www.intchopen.)”

Spelt and emmer flours

by luciano

Premise: the research highlighted the importance of sourdough made with selected LABs and with autochthonous ones of emmer and spelt flour to fully exploit the potential of these “ancient grains”. The optimum will be, therefore, starting from a sourdough with a selection of lactobacilli (LAB) and refreshing it with the flours in question, thus making the contribution of the Lab present in the same flours.

“Lactobacillus brevis 20S, Weissella confusa 24S and Lact. plantarum 31S were used as pool 1 to start spelt flour. Lactobacillus plantarum 6E, Lact. plantarum 10E and W. confusa 12E were used as pool 2 to start emmer flour. ‘Ancient grains’ could serve as an abundant source of protein and soluble fibre, oleic acid and macro- and micro-elements (Bonafaccia et al. 2000; Ruibal-Mendieta et al. 2005). In spite of this increasing interest, few results are available on the microbiota of spelt and emmer and on their suitability for bread making. Selection of starters within endogenous strains was considered the most important pre-requisite. Some recent studies (Di Cagno et al. 2008a,b,c) on fermented vegetable foods, which also included strains of Lact. plantarum, have clearly shown that endogenous strains are preferred to those of the same species isolated from different matrices to promote a rapid and intense process of acidification with a positive influence on nutritional and technological properties. To use, mixed starters was considered functional to completely exploit the potential of spelt and emmer flours. Mixture of strains with dif- ferent carbohydrate metabolism is frequently used because it may guarantee optimal acidification and sensory properties (Gobbetti 1998). Mixed obligate and facultative heterofermentative lactic acid bacteria starters, as selected in pool 1 and 2, ensured rapid growth and acidification, the capacity to liberate FAA and exploited the rheology, sensory and nutritional properties of the raw flours. This was according to a two-step fermentation process. The use of sourdough comprising selected and autochthonous strains of lactic acid bacteria was considered the most suitable biotechnology to exploit the potential of spelt and emmer flour in bread making. Fermentation of spelt, emmer or wheat flours by pool 1 and 2 was allowed according to a two-step fermentation process (Fig. 1). As the general rule, it was possible to keep it lower than 4Æ0 in spelt and emmer sourdoughs, which implied a considerable synthesis of acetic acid (Gobbetti et al. 2005). Acidity of spelt and emmer breads was perceived through sensory analysis and positively influenced the volume and crumb grain of breads. Flavour of bread is known to be influenced by the combination of raw materials, fermentation and baking process (Gobbetti et al. 2005). Spelt and emmer sourdough breads received the highest score for acid taste, and a clear preference for the global taste was assigned to spelt sourdough bread. First, this study showed the suitability of spelt and emmer flours to be used for bread making according to a two-step fermentation process. Sourdough biotechnology based on selected starters was indispensable to completely exploit the potential of these ‘ancient grains’. Spelt and emmer flours were purchased from a local market. The characteristics of emmer flour were water content, 15,0%; protein (N · 5,70), 15,1% of dry matter (d.m.); fat, 2,5% of d.m.; ash, 1,9% of d.m.; and total soluble carbohydrates, 2,6% of d.m. The characteristics of spelt flour were water content, 15,0%; protein (N · 5,70), 19,1% of d.m.; fat, 2,2% of d.m.; ash, 2,0% of d.m.; and total soluble carbohydrates, 2,7% of d.m. Spelt and emmer flours: characterization of the lactic acid bacteria microbiota and selection of mixed starters for bread making. (
R. Coda, L. Nionelli, C.G. Rizzello, M. De Angelis, P. Tossut and M. Gobbetti. 1 Department of Plant Protection and Applied Microbiology, University of Bari, Bari, Italy 2 Puratos N. V., Industrialaan, 25 B-1702z, Groot-Bijgaarden, Belgium. 2009).”

The fundamental importance of maturation

by luciano

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 [38]. 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).

Maturation and fermentation of a mixture of water, flour and yeasts and / or lactic bacteria

by luciano

Maturation and fermentation are just two of the many processes that take place within a dough: they are not the same thing and they must not be confused with each other. The general concept of “fermentation” is known and is quite well known and is understood as the complex of biological reactions involving the transformation of sugars as the lactic fermentation and the alcohol. During such metabolisms part of the sugars present in the dough are transformed by the yeast and by bacteria into acids, carbon dioxide, water, ethyl alcohol, energy etc.. and macroscopically result in a lowering of the pH value, in the production of aromatic substances and / or volatile, in gas production and in the increase of the dough mass. The term “maturation” on the other hand, refer to the complex of countless biochemical reactions that is the basis of cleavage or enzymatic breakdown of complex molecules into simpler molecules; macromolecules from complex to simple amino acids in the case of proteins, in the case of polysaccharides to monosaccharides. These reactions take long time, while the fermentation is much faster; the fermentation, however, can be slowed down very much if the dough is placed at rest in a low temperature (from 1 ° C to 4 ° C max). In this way we give the opportunity to the dough to mature; only to maturation occurred will choose to operate the gradual raising of the temperature in order to increase, to balance and optimize the fermentation process. Prolonghed fermentation and maturation also have an influence, not secondary, both on the shelf life both on the organoleptic characteristics of the finished product conferring, between the other, perfumes and flavors emphasized.


The fundamental importance of maturation