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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 Komlenić, Vedran Slačanac 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 Komlenić, Vedran Slačanac and Marko Jukić Faculty of Food Technology, Josip Juraj Strossmayer University of Osijek, Croatia 2012- www.intchopen.)”

Quantitation of the immunodominant 33-mer peptide from α-gliadin in wheat flours

by luciano

In wheat there are multiple fractions able to activate the adverse response of the human immune system. Among these fractions the most active is that called 33-mer because it is the most resistant to human digestion and because it contains six copies of the three toxic epitopes and its intermolecular bonds are very strong. It is therefore important to know the quantity of this fraction in the grains. The study of which some parts are reported, examined 57 different types of wheat, ancient and modern, noting that the difference, in all soft wheat and spelt flour, of 33-mer is wide: from 90.9 to 602.6 μg / g made with flour. On the other hand, its presence in monococcum wheat and durum wheat was not detected. These results take on great importance because they allow grains to be chosen with limited or no presence of this important toxic fraction for products that are more suitable for non-celiac gluten sensitive people or those suffering from gluten disorders.

“All gluten protein fractions, namely the alcohol-soluble prolamins and the insoluble glutelins, contain CD-active epitopes3. The prolamin fraction is particularly rich in proline and glutamine and the numerous proline residues lead to a high resistance to complete proteolytic digestion by human gastric, pancreatic, and brushborder enzymes. Studies by Shan et al. (2002) showed that a large 33-mer peptide (LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF) from α2-gliadin (position in the amino acid sequence of α2-gliadin: 56–88) is resistant to cleavage by intestinal peptidases4,5. The 33-mer is widely called the most immunodominant gluten peptide4,6,7, because it contains three overlapping T-cell epitopes, namely PFPQPQLPY (DQ2.5-glia-α1a, one copy), PYPQPQLPY (DQ2.5-glia-α1b, two copies) and PQPQLPYPQ (DQ2.5-glia-α2, three copies)3, which result in the initiation of a strong immune response.

Potential Health Benefits of Einkorn-Based Breads

by luciano

The research we present can be considered the first integrated assessment of the potential benefits, linked to the excellent nutritional properties, of the use for bread and derivatives of Einkorn. The research emphasizes the use of whole wheat flour and sourdough is essential to obtain the best results in terms of exploiting the potential of this grain. The choice of this grain is well summarized in a passage of research: “Einkorn (Triticum monococcum L. ssp. monococcum) is an ancient crop. Compared to polyploid wheats it has a higher content of proteins, polyunsaturated fatty acids, fructans, and phytochemicals as tocols, carotenoids, alkylresorcinols, phytosterols, and a lower α-, β-amylase and lipoxygenase activities [15]. In addition, einkorn expresses very few T-cell stimulatory gluten peptides [16]. Einkorn could represent a valid alternative for producing functional baked products.

“Abstract: Nowadays the high nutritional value of whole grains is recognized, and there is an increasing interest in the ancient varieties for producing wholegrain food products with enhanced nutritional characteristics. Among ancient crops, einkorn could represent a valid alternative. In this work, einkorn flours were analyzed for their content in carotenoids and in free and bound phenolic acids, and compared to wheat flours. The most promising flours were used to produce conventional and sourdough fermented breads. Breads were in vitro digested, and characterized before and after digestion. The four breads having the best characteristics were selected, and the product of their digestion was used to evaluate their anti-inflammatory effect using Caco-2 cells. Our results confirm the higher carotenoid levels in einkorn than in modern wheats, and the effectiveness of sourdough fermentation in maintaining these levels, despite the longer exposure to atmospheric oxygen. Moreover, in cultured cells einkorn bread evidenced an anti-inflammatory effect, although masked by the effect of digestive fluid. This study represents the first integrated evaluation of the potential health benefit of einkorn-based bakery products compared to wheat-based ones, and contributes to our knowledge of ancient grains.