Jussi Loponen

Degradation of HMW Glutenins During Wheat Sourdough Fermentations

ABSTRACT Bakeries use sourdoughs to improve bread properties such as flavor and shelf life. The degradation of gluten proteins during fermentation may, however, crucially alter the gluten network formation. We observed changes that occurred in the HMW glutenins during wheat sourdough fermentations. As fermentation starters, we used either rye sourdough or pure cultures of lactobacilli and yeast. In addition, we incubated wheat flour (WF) in the presence of antibiotics under different pH conditions. The proteolytic activities of cereal and sourdough-derived proteinases were studied with edestin and casein. During sourdough fermentations, most of the highly polymerized HMW glutenins degraded. A new area of alcohol-soluble proteins (≈30.000 MW) appeared as a result of the proteolytic breakdown of gluten proteins. Very similar changes were observable as WF was incubated in the presence of antibiotics at pH 3.7. Cereal and sourdough-derived proteinases hydrolyzed edestin at pH 3.5 but showed no activity at pH ...

LC-MS/MS quantification of bioactive angiotensin I-converting enzyme inhibitory peptides in rye malt sourdoughs.

This study quantified antiotensin I-converting enzyme (ACE) inhibitory peptides in rye malt sourdoughs supplemented with gluten proteins and fermented with six strains of Lactobacillus spp. Bioinformatic analysis of prolamins from barley, rye, and wheat demonstrated that the ACE inhibitory peptides LQP, LLP, VPP, and IPP are frequently encrypted in their primary sequence. These tripeptides were quantified by liquid chromatography-tandem mass spectrometry. Tripeptide levels in sourdoughs were generally higher as compared to the chemically acidified controls. Sourdoughs fermented with different strains showed different concentrations of LQP and LLP. These differences corresponded to strain-specific differences in PepO and PepN activities. The highest levels of peptides VPP, IPP, LQP, and LLP, 0.23, 0.71, 1.09, and 0.09 mmol (kg DM)(-1), respectively, were observed in rye malt: gluten sourdoughs fermented with Lactobacillus reuteri TMW 1.106 and added protease. These concentrations were 6-7 times higher as compared to sourdough without fungal protease and exceed the IC(50) by 100-1000-fold.

Prolamin hydrolysis and pentosan solubilization in germinated-rye sourdoughs determined by chromatographic and immunological methods.

The assortment and quality of bakery products designed for celiac patients may be improved by designing whole grain ingredients with low residual prolamin contents. The main objective of this study was to evaluate the extent of prolamin hydrolysis and pentosan solubilization in germinated-rye sourdoughs (GRSDs). Size-exclusion chromatography analyses, the fate of fluorescent prolamin, and immunological analyses determined the extent of prolamin hydrolysis and pentosan solubilization. Hydrolysis of rye prolamins was extensive in GRSDs, and according to enzyme-linked immunosorbent assay analyses, more than 99.5% of the prolamins were hydrolyzed. Pentosan solubilization occurred in native-rye sourdoughs, whereas in GRSDs, pentosans were partially hydrolyzed to monosaccharides. Test baking showed that the use of GRSD improved the overall quality of oat bread and that an estimated daily gluten intake from 100 g of bread would be less than 10 mg. However, the clinical safety must be assured before making any recommendations for celiac patients to use such products.

Angiotensin converting enzyme inhibitory peptides in Finnish cereals: a database survey

Angiotensin converting enzyme (ACE) regulates blood pressure (BP) by hydrolytic actions. ACEinhibitors are widely used in the pharmacological treatment of hypertension. Certain food-derived peptides can also inhibit the activity of ACE. This study shows the occurrences of known ACE-inhibitory peptides in cereal storage protein structures. A literature search yielded thirty-nine candidate peptides. Of these, twenty-two peptides were found to occur in the cereal storage proteins. For instance, of the tripeptides (isoleucine-proline-proline or valine-proline-proline) that lower BP in fermented milk products either one appears in cereal prolamins. In addition, oat globulins possess seven of the candidate peptides in their structures, whereas tripeptides leucine-glutamine-proline (LQP) and valine-serine-proline (VSP) occur repeatedly in C-hordeins and u-secalins (LQP), and D-hordeins (VSP). Cereal storage proteins, thus, appeared as potential sources of ACE-inhibitory peptides. Novel cereal products with BP-lowering effects may be developed by liberation of the target peptides.;

Randomised clinical trial: low‐FODMAP rye bread vs. regular rye bread to relieve the symptoms of irritable bowel syndrome

Grains are high in FODMAPs (Fermentable Oligo‐, Di‐, Monosaccharides And Polyols) and often considered as triggers of IBS symptoms.

Degradation of Secalins During Rye Sourdough Fermentation

ABSTRACT Rye sourdough (RSD) gives rye bread mildly acidic taste and desired flavor. Flavor precursors (amino acids and small peptides) are generated in the proteolytic breakdown of rye proteins. Our aim was to study the protein degradation during RSD fermentations. Two sourdoughs were prepared of flours derived from two rye cultivars (Amilo and Akusti). RSD samples were collected during fermentations. Three protein fractions were obtained by sequential protein extraction and these were analyzed by SDS-PAGE. Free amino nitrogen (FAN) was measured with a ninhydrin method. In addition, two rye incubations without starter microorganisms (with antibiotics) were made at pH 3.6 and 6.1, and proteinase profiles of the rye cultivars were analyzed at pH 4.3. SDS-PAGE analysis showed that during RSD fermentations, rye proteins, especially the alcohol-soluble secalins, were degraded. Secalins also evidently degraded during the incubation without starter microorganisms at pH 3.6. Aspartic proteinases were in the majo...

Foaming of Differently Processed Oats: Role of Nonpolar Lipids and Tryptophanin Proteins

ABSTRACT The baking properties of oats are poor, mainly due to the lack of gluten matrix and hence the surface properties of the aqueous phase are crucial for the gas retention in oat dough. Our aim was to study the composition and foaming properties of the water-soluble fraction from differently processed oats. A water extract from kilned oats contained nonpolar triglycerides and had poor foaming properties, whereas removing lipids with hexane extraction improved the foaming capacity and foam stability. A water extract from supercritical carbon dioxide extracted oats (CO2-oats) was free from nonpolar lipids and had good foam stability and excellent foaming capacity. Moreover, oat lipid-binding proteins, tryptophanins, were highly concentrated in the CO2-oats-derived foam and apparently played an important role in the foam structure. Supplementing CO2-oats extract with small quantities (<0.05%) of nonpolar lipids of oats destructed its foaming properties. In a preliminary baking trial, the addition of the...

Influence of Thiol Metabolism of Lactobacilli on Egg White Proteins in Wheat Sourdoughs

In wheat sourdoughs, the degradation of gluten proteins is favored by acidification and reducing conditions. This study aimed to determine the proteolytic degradation of egg white proteins in wheat sourdoughs acidified with lactobacilli differing in their thiol metabolism. Ovotransferrin was the only major egg white protein that degraded during sourdough fermentations. An extensive degradation of ovotransferrin required a heterofermentative lactobacilli starter, Lactobacillus sanfranciscensis, with glutathione reductase activity. Ovotransferrin was more resistant to breakdown when sourdoughs were acidified with homofermentative lactobacilli or a mutant strain of L. sanfranciscensis lacking the glutathione reductase. Its susceptibility to proteolysis in L. sanfranciscensis sourdoughs is thus attributable to thiol accumulation by L. sanfranciscensis, which apparently altered the structure of ovotransferrin through a reduction of disulfide bonds. Proteolytic degradation of ovotransferrin was attributable to wheat aspartic proteinases. In addition to the susceptibility to proteolysis, other functional properties of egg proteins may be influenced by thiol-exchange reactions.

Oxidative modification of a proline-rich gliadin peptide

Prolamins are proline-rich proteins occurring in cereal grains. Prolamins of wheat, barley and rye, or gluten protein, can cause coeliac disease in individuals not tolerating gluten. Degrading harmful prolamins can reduce their toxicity. A model peptide sequenced in α-gliadin, 33-mer (LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF), was chosen for our study. The metal-catalysed oxidation of 33-mer was studied, instead of enzymatic hydrolysis. Peptide 33-mer was treated in several oxidative systems. Iron-catalysed hydrogen peroxide-induced oxidation showed the greatest modification of 33-mer. Carbonyl groups and dityrosine cross-links were readily formed. At best, the immunological activity of 33-mer was reduced to 18% of its initial level after 24h of oxidation. Oxidative treatment can be further applied for the modification of cereal prolamin proteins, since it appears to be a potential alternative for reduction of coeliac immunological activities in gluten proteins.

Testing safety of germinated rye sourdough in a celiac disease model based on the adoptive transfer of prolamin-primed memory T cells into lymphopenic mice

UNLABELLED The current treatment for celiac disease is strict gluten-free diet. Technical processing may render gluten-containing foods safe for consumption by celiac patients, but so far in vivo safety testing can only be performed on patients. We modified a celiac disease mouse model to test antigenicity and inflammatory effects of germinated rye sourdough, a food product characterized by extensive prolamin hydrolysis. Lymphopenic Rag1-/- or nude mice were injected with splenic CD4+CD62L-CD44high-memory T cells from gliadin- or secalin-immunized wild-type donor mice. We found that: 1) Rag1-/- recipients challenged with wheat or rye gluten lost more body weight and developed more severe histological duodenitis than mice on gluten-free diet. This correlated with increased secretion of IFNγ, IL-2, and IL-17 by secalin-restimulated splenocytes. 2) In vitro gluten testing using competitive R5 ELISA demonstrated extensive degradation of the gluten R5 epitope in germinated rye sourdough. 3) However, in nude recipients challenged with germinated rye sourdough (vs. native rye sourdough), serum anti-secalin IgG/CD4+ T helper 1-associated IgG2c titers were only reduced, but not eliminated. In addition, there were no reductions in body weight loss, histological duodenitis, or T cell cytokine secretion in Rag1-/- recipients challenged accordingly. IN CONCLUSION 1) prolamin-primed CD4+CD62L-CD44high-memory T cells induce gluten-sensitive enteropathy in Rag1-/- mice. 2) Hydrolysis of secalins in germinated rye sourdough remains incomplete. Secalin peptides retain B and T cell stimulatory capacity and remain harmful to the intestinal mucosa in this celiac disease model. 3) Current antibody-based prolamin detection methods may fail to detect antigenic gluten fragments in processed cereal food products.