Effects of Acidification, Sodium Chloride, and Moisture Levels on Wheat Dough: I. Modeling of Rheological and Microstructural Properties

Effect of sourdough on the quality of whole wheat fresh noodles fermented with exopolysaccharide lactic acid bacteria

In this study, the impact of exopolysaccharides (EPS)-positive strain Weissella cibaria (W. cibaria) fermented sourdough on the quality of whole wheat fresh noodles (WWNs) and its improvement mechanisms were studied. The optimal fermentation conditions were found to be 30% sucrose content, fermented at 25 °C for 12 h, which yielded the highest EPS, 28.06 g/kg, in the W. cibaria fermented sourdough with sucrose (DW+). During storage, the sourdough reduced polyphenol oxidase activities and delayed the browning rate of noodles. The DW+ increased the hardness by 11.98% from 2184.99 to 2446.83 g, and the adhesiveness increased by 19.60%, i.e., from 72.01 to 86.13 g∙s of the noodles. The EPS mitigated acidification of sourdough, prevented the disaggregation of glutenin macropolymers (GMP), and increased sourdough elastic modulus. In addition, scanning electron microscope and confocal laser scanning microscopy of noodles containing EPS sourdough also demonstrated the uniform distribution of gluten proteins. The starch granules were also closely embedded in the gluten network. Thus, the present work indicated that the EPS produced sourdough delayed browning and improved the WWNs texture, indicating its potential to enhance the quality of whole grain noodles.

A dynamic micro-scale dough foaming and baking analysis - Comparison of dough inflation based on different leavening agents

Leavening agents play a pivotal role in the production of baked goods. Through gas production the inner structure of the product gets its typical foam structure and textural appearance. Baking trials are thereby a common way to determine the achievable loaf volume, crumb structure and other product specific properties. The required material input for these classic baking trials is high, as well as specific baking skills are required to obtain comparable and reliable results. To minimize the previously mentioned challenges, an in-line kneading, proofing, and baking process in a conventional rheometer was used and a microscale method was developed to determine both flour-specific baking performance and leavening-dependent volume increase without sample transfer. The results show a direct comparability of standard baking tests and the microscale method with yeast. In a second step the influence of the commercial used acidifying agent in baking powder D-(+)-Glucono-1,5-lactone (GDL) was compared to l-galactono-1,4-lactone (GGL), an alternative that has the potential to be biotechnologically produced from pectin-rich plant biomass residues. The results showed that GGL produced carbon dioxide slower then GDL and could therefore be interesting for frozen or slow rising products especially for protein rich flours.

Sodium chloride replacement by potassium chloride in bread: Determination of sensorial potassium threshold and effect on dough properties and breadmaking quality

High sodium intakes represent an important risk factor for hypertension, cardiovascular diseases and kidney diseases. Even during the current COVID-19 pandemic, hypertension was related to higher mortality rate in patients with coronavirus. Thus, it is necessary to apply strategies to reduce or replace sodium content in food most widely consumed, like bread. This work aimed at determining the sensorial potassium threshold when potassium chloride is used as a sodium chloride replacer in bread formulation, and at analyzing the effects of such replacement on the properties of dough and on the technological and sensorial quality of bread. A decrease was observed in dough rheological properties with NaCl reduction in the formulation. Sensorial potassium threshold was determined and KCl was used in bread formulation as a NaCl replacement up to 0.92% of the regular salt content (2%) undetected by its characteristic taste. NaCl reduction resulted in bread with lower specific volume, higher firmness, faster staling and clearer crust. KCl bread showed similar technological to 2% NaCl bread. Finally, it was possible to replace 50% of NaCl with KCl without reducing quality and consumer acceptability.

Water Absorption Capacity Determines the Functionality of Vital Gluten Related to Specific Bread Volume

Vital gluten is often used in baking to supplement weak wheat flours and improve their baking quality. Even with the same recipe, variable final bread volumes are common, because the functionality differs between vital gluten samples also from the same manufacturer. To understand why, the protein composition of ten vital gluten samples was investigated as well as their performance in a microbaking test depending on the water content in the dough. The gluten content and composition as well the content of free thiols and disulfide bonds of the samples were similar and not related to the specific bread volumes obtained using two dough systems, one based on a baking mixture and one based on a weak wheat flour. Variations of water addition showed that an optimal specific volume of 1.74–2.38 mL/g (baking mixture) and 4.25–5.49 mL/g (weak wheat flour) was reached for each vital gluten sample depending on its specific water absorption capacity.

Definition of network types - Prediction of dough mechanical behaviour under shear by gluten microstructure

This study defines network types of wheat gluten to describe spatial arrangements of gluten networks in relation to dough mechanical behaviour. To achieve a high variety in gluten arrangements, ten specific and unspecific gluten-modifying agents in increasing concentrations were added to wheat dough. Gluten microstructure was visualized by confocal laser scanning microscopy and quantified by protein network analysis. Dough rheological behaviour was determined by both oscillatory and creep-recovery tests. Based on correlation matrices and principal component analysis, six different network types were identified and associated to their rheological characteristics: a cleaved (low viscous), rigid (highly viscous), spread (viscoelastic), strengthened (viscoelastic), particulate and dense (highly viscous) or particulate and loose (low viscous) network. Furthermore, rheological dough properties of specifically gluten-modified samples were predicted with five microstructural gluten attributes (lacunarity, branching rate, end-point rate, protein width, average protein length) and assigned properly by the obtained partial least square model with an accuracy up to 90% (e.g., R2Y = 0.84 for G*, 0.85 for tanδ, 0.90 for Jmax). As a result, rheological properties of wheat doughs were predicted from microstructural investigations. This novel, quantitative definition of the relation between structure and mechanical behaviour can be used for developments of new wheat products with targeted properties.

Concentration dependent rate constants of sodium substitute functionalities during wheat dough development

Chloride salts can serve as sodium chloride (NaCl) substitutes in wheat dough for sensory or technological reasons. Therefore, the effect of different substitutes on wheat dough development during mixing (optimum water absorption, dough development time, stability) and fermentation (maximum dough height) with a material-adapted water addition and mixing time were investigated. The substitutes had effects on all measures at a level of 2 g salt 100 g^-1 wheat flour, with the exception of KCl. The intensity of the effect significantly followed the Hofmeister series due to an altered hydration behavior of the structure-determining gluten proteins. The experiments were supported by CLSM micrographs combined with image analysis. Next to an absolute substitution, the main focus of the study were concentration dependent functionalities of the chloride salts. Therefore, concentration dependent rate constants were calculated based on the application of different concentration levels of the chloride salts. These rate constants showed in all cases a similar tendency following the Hofmeister series.

Substitution of sodium chloride by salt microspheres in dough: Effect on dough rheological properties

This research aimed to evaluate the impact of different salts on dough rheology parameters and gas cell development during dough preparation. Three types of salts in four concentrations each were used in dough preparation and following analyses were conducted: sodium content, salt structure analysis, dough hardness, dough stickiness and dough image analysis. The research showed how significantly (p < .05) the measured properties of dough can be influenced by the used type of salt, salt concentrations and fermentation time. The emphasis is put on salt substitutes of hollow microsphere salt (Hs) substitutes due to its special physical characteristics. The uniqueness of Hs physical characteristics was confirmed by electron microscope photomicrographs. The gained results are indicating that even low changes in salt concentration (0.40; 0.30; 0.25; and 0.15) make noticeable changes in dough characteristics. The usage of salt substitutes in food industry has been constantly growing and it makes the research a valuable source of information for further application of this salts.

PRACTICAL APPLICATIONS

The different salt types (table-Ts, sea-Ss and hollow microsphere-Hs) which were studied in our work differ just slightly. However, an important issue in choosing salt should also be the nutritive perspective, in particular low sodium content as a preventive measure against cardio-vascular diseases. Hs and Ss are therefore suitable alternatives to typical Ts.

Physico-chemical and metabolomic characterization of KAMUT® Khorasan and durum wheat fermented dough

Investigations were made in order to evaluate the influence of the flour type, chemical acidification and fermentation on characteristics of doughs obtained with durum wheat and KAMUT® Khorasan flour. Doughs were observed immediately after mixing, 90 and 360 min of leavening at 30 °C. Fundamental rheology, yeasts heat production by isothermal microcalorimetry and the interaction between water and biopolymers by means of time domain nuclear magnetic resonance were evaluated. In addition aromatic metabolite development was followed by means of the combined application of gas-chromatography and electronic nose. KAMUT® Khorasan flour was found to be more suitable than durum wheat for the fermentation processes tested, especially at acidic conditions, as shown by the increase of the volume and the metabolic heat production by yeast. In acidified dough the pattern of volatile metabolites allowed a clear distinction between the types of dough. Moreover the water/starch proton pool was characterized by higher T2 values in the KAMUT® Khorasan samples.

Impact of wheat bran derived arabinoxylanoligosaccharides and associated ferulic acid on dough and bread properties

The impact of arabinoxylanoligosaccharides (AXOS) with varying bound or free ferulic acid (FA) content on dough and bread properties was studied in view of their prebiotic and antioxidant properties. AXOS with an FA content of 0.1-1.7% caused an increase in dough firmness with increasing AXOS concentration. AXOS with a high FA content (7.2%), on the contrary, resulted in an increase in dough extensibility and a decrease in resistance to extension, similar to that for free FA, when added in levels up to 2%. Higher levels resulted in unmanageable dough. A limited impact on dough gluten network formation was observed. These results suggest that for highly feruloylated AXOS, the FA-mediated dough softening supersedes the firming effect displayed by the carbohydrate moiety of AXOS. The impact of the different AXOS on bread volume, however, was minimal. Furthermore, AXOS in bread were not engaged in covalent cross-linking and significantly increased its antioxidant capacity.