Tuula Sontag-Strohm

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 ...

Viscosity of beta-glucan in oat products

Kauran jyva, kauran ydin sisaltaa 3-4 % ns. vaihtuvasidoksellistabeetaglukaania, jossa glukoosiyksikot liittyvat haaroittumattomaksi ketjuksi s(1 4)- ja s(1 3)-sidoksin. Ravitsemuksellisesti kauran beetaglukaani luetaan liukoiseen, suolensisallon viskositeettia lisaavaan ravintokuituun, jolla on kahdenlaisia terveytta edistavia vaikutuksia, nimittain verensokerin glukoosi- ja insuliinitasoja tasaava vaikutus ja kolesterolitasoa alentava vaikutus. Suolensisallon viskositeetin kasvu hidastaa glukoosin imeytymista ja heikentaa kolesterolin ja sen rakennusaineiden, sappihappojen, imeytymista. Vaikka beetaglukaanin viskositeetilla on siten ilmeisen tarkea merkitys sen fysiologisten vaikutusten kannalta, sen mittaamisen analytiikkaan on kiinnitetty suhteellisen vahan huomiota. Vain muutamissa kauratuotteiden kliinisissa kokeissa on kunnolla kuvattu beetaglukaanin viskositeetti. Elintarvikkeessa ja sen ruokasulassa beetaglukaanista johtuva viskositeetti riippuu beetaglukaanin liukenevuudesta, konsentraatiosta ja molekyylipainosta. Kun pyritaan valmistamaan kauran beetaglukaaniin perustuvia terveysvaikutuksia omaavia elintarvikkeita, valmistuksessa on kiinnitettava huomiota raaka-aineen beetaglukaanin maaran ja pitoisuuden (annoksen) lisaksi myos prosessointimenetelmaan. Menetelman tulee taata beetaglukaanin riittava liukoisuus ja minimoida sen hajoaminen esimerkiksi entsymaattisesti. Tutkimustemme kohteena ovat olleet eri elintarvikeprosessit ja niissa kaytetyt suuren beetaglukaanipitoisuuden omaavat kaurafraktiot seka toisaalta beetaglukaanin viskositeetin maaritysmenetelman kehittaminen. Tassa katsauksessa pohditaan eri nakokohtia kehitettaessa sellaista beetaglukaanin viskositeetin maaritysmenetelmaa, joka pystyisi kuvaamaan ja ennakoimaan beetaglukaanin kayttaytymista prosesseissa ja fysiologisesti.

Liquefaction of hydrothermally pretreated wheat straw at high-solids content by purified Trichoderma enzymes

Enzymatic liquefaction was studied by measuring continuously the flowability change of high-solids lignocellulose substrates using a real time viscometric method. Hydrolysis experiments of hydrothermally pretreated wheat straw were carried out with purified enzymes from Trichoderma reesei; Cel7A, Cel6A, Cel7B, Cel5A, Cel12A and Xyn11A. Results obtained at 15% (w/w) solids revealed that endoglucanases, in particular Cel5A, are the key enzymes to rapidly reduce the viscosity of lignocellulose substrate. Cellobiohydrolases had only minor and the xylanase practically no effect on the viscosity. Efficient, fast liquefaction was obtained already at a dosage of 1.5 mg of Cel5A/gdrysolids. Partial replacement or supplementation of Cel5A by the other major hydrolytic enzymes did not improve the liquefaction. The reduction of viscosity did not correlate with the saccharification obtained in the same reaction, suggesting that efficient liquefaction is rather dependent on the site than the frequency of enzymatic cleavages.

Oat Bran Fermentation by Rye Sourdough

ABSTRACT Hydration of oat bran including fermentation by rye sourdough was studied. Three types of oat bran suspensions were prepared (a control, one with whole meal rye flour added, and one with rye starter added). The suspensions were incubated for 1, 2, 3 and 4 hr. β-Glucan content and solubilities of protein and β-glucan were analyzed. Viscosity of the supernatants of oat bran suspensions was determined. Neither the rye sourdough nor the rye flour alone had a significant effect on the total β-glucan content of oat bran suspensions. However, the addition of rye, either as whole meal rye flour or as sourdough starter, markedly increased the solubility of β-glucan and proteins and simultaneously decreased the viscosity of the water-soluble fraction of oat bran suspension. This suggests that a hydrolysis of β-glucan had occurred that could change the rheological properties of oat bran in baking and the physiological potential of oat bran in nutrition.

Nutritive quality and protein production from grain legumes in a boreal climate.

BACKGROUND Boreal cropping systems are heavily focused on the production of small-grain cereals; to improve their resilience to climate change and to achieve food and feed security, diversification is needed. This study investigated the potential of faba bean, narrow-leafed lupin and lentil as protein crops in southern Finland, where faba bean is traditional but the other two are novel. RESULTS Early cultivars of narrow-leafed lupin and lentil matured adequately. Protein concentration in faba bean was, at 32%, higher than the world average of 29%, while those of narrow-leafed lupin and lentil were close to their world averages. Protein yields decreased in the order faba bean > narrow-leafed lupin > lentil. Lipid content of faba bean and lentil was about 1.2% and that of narrow-leafed lupin about 5.5%, and fatty acid composition was largely oleic and linoleic in all three species. CONCLUSION Both lentil and narrow-leafed lupin can be added to the range of feed and food crops produced at high latitudes in Europe. While faba bean produces the greatest protein yield and lysine concentration, the higher sulfur amino acid concentration in lupin, its oil content and its adaptation to acid, sandy soils not suitable for faba bean make it an attractive alternative.

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...

In situ enrichment of folate by microorganisms in beta-glucan rich oat and barley matrices.

The objective was to study folate production of yeast strains, bacteria isolated from oat bran, and selected lactic acid bacteria as well as one propionibacterium in oat and barley based models. Simultaneously, we aimed at sustaining the stability of viscosity, representing the physicochemical state of beta-glucan. Total folate contents were determined microbiologically and vitamers for selected samples by UHPLC. Folate in yeast cells comprised mainly 5-methyltetrahydrofolate and tetrahydrofolate. Folate production by microbes in YPD medium was different to that in cereal fermentations where vitamers included 5-methyltetrahydrofolate, 5,10-methenyltetrahydrofolate and formylated derivatives. Microbes producing significant amounts of folate without affecting viscosity were Saccharomyces cerevisiae ALKO743 and Candida milleri ABM4949 among yeasts and Pseudomonas sp. ON8 and Janthinobacterium sp. RB4 among bacteria. Net folate production was up to 120 ng/g after 24 h fermentation and could increase during 2-week storage. Glucose addition increased the proportion of 5-methyltetrahydrofolate. Streptococcus thermophilus ABM5097, Lactobacillus reuteri, and Propionibacterium sp. ABM5378 produced folate but in lower concentrations. Both endogenous and added microbes contribute to folate enhancement. Selection of microbes with folate producing capability and limited hydrolytic activity will enable the development of products rich in folate and beta-glucan.

The oxidative degradation of barley β-glucan in the presence of ascorbic acid or hydrogen peroxide

Cereal β-glucans are polysaccharides with health benefits that have been linked to their ability to increase luminal viscosity. However, the functional properties of cereal β-glucans may be diminished by the susceptibility of this polysaccharide to oxidative degradation. In this study, barley β-glucan was oxidised with hydrogen peroxide or ascorbic acid and the oxidative degradation of β-glucan was investigated using both asymmetrical flow field-flow fractionation (AsFlFFF) with aqueous solvent and high performance size exclusion chromatography (HPSEC) with LiBr in DMSO as the solvent. Oxidation was shown to cause degradation of β-glucan, the reaction being faster when oxidised with hydrogen peroxide compared with ascorbic acid. Both HPSEC and AsFlFFF showed comparable results as long as aggregates (only observed in AsFlFFF) were not included in the integration. The compact aggregates observed in oxidised samples suggest oxidation driven interactions between β-glucan molecules.

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...

Production of folate in oat bran fermentation by yeasts isolated from barley and diverse foods

The focus of the research was to identify yeasts from barley kernels in order to study their folate production capability while maintaining high viscosity caused by soluble fibres in oat bran fermentation.