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Sourdough lactic acid bacteria and products for Celiac Susceptible People

by luciano

The lactic acid bacteria present in the sourdough have been shown to have significant abilities to hydrolyze gluten proteins; some strains of lactic bacteria used with specific temperatures, times and concentrations can also hydrolyse the peptides most resistant to gastro-intestinal digestion. Baked products made with sourdough can therefore be considered an excellent opportunity and a valid choice for people genetically predisposed to celiac disease.

Extract from the study “ Gluten-Free Products for Celiac Susceptible People”:
A – “ omissis…… The 33-mer peptide from α2-gliadin (amino acid sequence positions 56–88, LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF) contains three overlapping T-cell epitopes (3 × PQPQLPYPQ, 2 × PYPQPQLPY and PFPQPQLPY) for CD sensitive individuals. The human gastrointestinal enzymes pepsin, trypsin, and chymotrypsin were unable to hydrolyze the 33-mer peptide due to their inability to cleave before or after proline or glutamine, leaving the epitopes intact. Comparatively, large CD immunogenic peptides (≥9 amino acid residues) reach the small intestine (11) after crossing through the epithelial barrier and initiate immunogenic cascade in the lamina propria.

B – “omissis …Wheat flours modified to eliminate or reduce the immune toxicity of gluten have been used to prepare pasta and baked products. The large peptides of gluten need to be modified/converted into peptides of <9 amino acid residues to minimize the CD-induced immunoreactivity. This has been achieved through numerous approaches, including exogenous enzyme treatment, use of sourdough/lactic acid bacteria, use of genetically modified wheat, etc.”

C – “ omissis…The sourdough was prepared by fermenting flour with naturally occurring lactic acid bacteria (LAB) and yeasts. In the mature sourdoughs, the lactic acid bacteria were higher in number (> 10cfu/g) than the number of yeasts. Type I sourdough has a final pH of 4.0 at room temperature (20–30C) and is manufactured by continuous daily refreshments with the aim to maintain the microorganisms in an active state. It takes 2–5 (>30C) days of fermentation for developing type II sourdough as an acidifier with a pH that is <3.5 after 24 h of fermentation (131). The microorganisms were used in the late stationary phase of growth and exhibited restricted metabolic activity. The type III sourdough, as an acidifier supplement and aroma carrier in bread making, is a dried powder used for fermentation by certain starter cultures. A few reports are available about the use of sourdough for the preparation of gluten-free bread (84, 85). In one study it was reported that food processing by selected sourdough lactobacilli and fungal proteases may be considered an efficient approach for eliminating gluten toxicity, reducing the gluten level below 12 ppm (119). Further, sourdough fermentation, usually with a mixture of lactic acid bacteria (LAB) and yeasts, is traditionally used to produce leavened bread, especially from rye flour. Lactobacillus sp. are predominant among lactic acid bacteria (LAB) and they produce numerous mixed proteolytic enzymes, including metalloendopeptidases, such as PepO and PepF; aminopeptidases, such as PepN and PepC; dipeptidases, such as PepD; and dipeptidyl and tripeptidylpeptidases, such as the proline-specific Xaa-Pro dipeptidyl-peptidase (PepX) (132). The combination of wheat germination and sourdough fermentation with Lactobacillus brevis L62 extensively hydrolyzed wheat prolamin down to <5% of the initial content (133). A cell-free extract of two LABs, L. plantarum and Pediococcus pentosaceus, had a higher gliadin-degrading capacity (83%) in doughs than the corresponding cell suspension (70%), and complete gliadin degradation without using live LAB may be optimized (134). High molecular weight polymers, namely exopolysaccharides, are produced by lactic acid bacteria in presence of sucrose that mimics physiochemical properties of commercial hydrocolloids or gums, such as the ability to form a network and bind water. It counteracts the negative effects of excessive sourdough acidification and enhances loaf volume, shelf-life, the staling rate, and textural properties of products (129).”

Depeening
Gluten-Free Products for Celiac Susceptible People. Sweta Rai, Amarjeet Kaur and C. S. Chopra. Front. Nutriens 17 december 2018.

Mutually stimulating interactions between lactic acid bacteria and Saccharomyces cerevisiae in sourdough fermentation

by luciano

“Interactions between microorganisms are key to their performance in food habitats. Improved understanding of these interactions supports rational improvement of food fermentations. This study aimed at identifying inter- actions between lactic acid bacteria and yeast during sourdough fermentation. Therefore, the lactic acid bacteria Lactobacillus plantarum and Lactobacillus sanfranciscensis were co-cultured with the yeast Saccharomyces cerevisiae in a newly developed medium, as well as in situ in a sourdough-like environment. L. sanfranciscensis was found to be stimulated by a secreted factor of S. cerevisiae in any tested in vitro situation, whereas L. plantarum and S. cerevisiae stimulated each other only in the presence of glucose, fructose and lactose as carbon source, but not with galactose, maltose, sucrose and starch. Moreover, it was demonstrated that L. sanfranciscensis is stimulated by CO2 and another yet to be identified factor produced by yeast in a sourdough-like environment. In conclusion, S. cerevisiae produces growth factors stimulatory to lactic bacteria. The nature and the efficacy of these growth factors depend on the target species and on the supplied carbon source. “Abstract della ricerca riportata negli Approfondimenti.

Depeening:

Mutually stimulating interactions between lactic acid bacteria and Saccharomyces cerevisiae in sourdough fermentation. Sander Sieuwerts, Peter A. Bron, Eddy J. Smid, Kluyver The Netherlands
 Wageningen University, Laboratory of Food Microbiology, P.O. Box 17, 6700 AA Wageningen, The Netherlands . LWT – Food Science and Technology 90 (2018) 201–206

Surdough fermentation (II part)

by luciano

Surdough and phytates
“Increasing fiber content in flour may result in a lower assimilation of minerals complexed by phytates. An optimisation of the fermentation step with surdough allowed to improve both the bioavailability of minerals as well as the sensory attributes of the resulted bread. (16mo. IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008 Archived at ttp://orgprints.org/view/projects/conference.html)”.

Note: Phytic acid is traditionally considered an anti-nutritional factor, ie a substance that can limit the absorption or use of nutrients. In the specific case, by binding to them to form insoluble salts (phytates and phytin), phytic acid hinders the absorption of some minerals (calcium, iron, magnesium and zinc).

Sourdough fermentation and basic baking properties
“Unfortunately, there is often a trade- off between degradation of reactive gluten and retention of gluten for basic baking properties. Large amounts of time and heat may be needed for microbial enzymes to break down problematic pep- tides. To fully degrade the 33-mer α-gliadin peptide in wheat required 24 h at 30 °C (Gallo and others 2005), while durum required 72 h of fermentation at 37 °C to meet gluten-free la- beling standards (De Angelis and others, 2010). HMW glutenins, which are important for baking and pasta integrity, are degraded prior to and more extensively than reactive prolamins during sour- dough fermentation (Ga ̈nzle and others 2008; Wieser and others 2008). Extensively fermented dough has a high ratio of gliadins to glutenins, which is very undesirable for bakers. The disulfide bonds holding together the gluten macropolymer (GMP), an in- tegral component of baking quality, begin to degrade long before glutens. Only 5 h of fermentation with Lactobacilli or acidic chem- icals degraded GMP by up to 46% (Wieser and others 2008). Pentosans, an important component for baking rye bread, were also hydrolyzed in germinated sourdough (Loponen and others 2009). Consequently, the long and hot sourdough fermentation to hydrolyze prolamins compromises functional baking properties of the dough. (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. Sorrells. Comprehensive Reviews in Food Science and Food Safety Vol. 14, 2015.)”.

Microbiology of sourdough
“It is well known that the type of bacterial flora developed in each fermented food depends on water activity, pH (acidity), minerals concentration, gas concentration, incubation temperature and composition of food matrix (Font de Valdez et. al. 2010). The microflora of raw cereals is composed of bacteria, yeast and fungi (104 – 107 CFU/g), while flour usually contains 2 x 104 – 6 x 106 CFU/g (Stolz, 1999). In sourdough fermentation major role play heterofermentative species of LAB (Salovaara, 1998; Corsetti & Settani, 2007), especially when sourdoughs are prepared in a traditional manner (Corsetti et. al., 2003). Lactobacillus sanfranciscensis, Lactobacillus brevis and Lactobacillus plantarum are the most frequently lactobacilli isolated from sourdough (Gobbetti, 1998; Corsetti et. al. 2001; Valmorri et. al., 2006; Corsetti & Settanni, 2007). The following yeasts have been detected in cereals (9 x 104 CFU/g) and flour (2 x 103 CFU/g): Candida, Cryptococcus, Pichia, Rodothorula, Torulaspora, Trychoporon, Saccharomyces and Sporobolomyces. Saccharomyces cerevisiae is not found in the raw materials. Its occurance in sourdough has been explained by the application of baker’s yeast in most daily bakery practice (Corsetti et. al., 2001). The importance of antagonistic and synergistic interactions between lactobacilli and yeasts are based on the metabolism of carbon hydrates and amino acids and the production of carbon dioxide (Gobetti & Corsetti 1997). Lactic and acetic acid are predominant products of sourdough fermentation). 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)”.