Fundamental Rheology Research Articles

Combination of empirical and fundamental rheology for the characterization of dough from wheat flours with different extraction rate

Empirical rheological techniques conventionally used for evaluating wheat flour dough can be coupled to fundamental rheology, especially when viscoelastic properties of dough, like those with high bran content, cannot be readily investigated using empirical rheology alone. In this study, the correlations between the two types of rheology were evaluated considering flours with different extraction rate, from refined to whole grain ones. From empirical tests it resulted that flours with higher protein and fibre contents required more water to be optimally hydrated, showing also longer dough developing time. Higher tenacity and lower extensibility were also observed. Fundamental rheology assessed the viscoelastic character of the dough with a predominantly solid-like behavior, and a direct correlation between flour extraction rate and dough consistency was found. Dough made from less refined flours was less deformable and showed a more elastic recovery ability. Starch gelatinization temperature and process rate, increased and decreased, respectively, with the extraction rate. The existing correlations between empirical and fundamental rheology were used to estimate the alveograph parameters of blends of type 00 soft wheat flour enriched with 15% and 20% ground soft wheat bran. Overall, the study has shown that the combination of the two rheological approaches is useful to determine the best use of high-fibre flours that could not be determined by the official empirical methods.

Nutritional Improvement of Fresh Cheese with Microalga Chlorella vulgaris: Impact on Composition, Structure and Sensory Acceptance.

The production of foods fortified with bioactive ingredients has been recognized by food companies as a way to position their products in health food markets. The fortification of cheese represents a major challenge, due to the chemical and structural complexity of the cheese matrix, as well as the complexity of the biochemical reactions occurring during the fermentation and maturation processes. Microalgae are nutritious and sustainable food sources with important bioactive compounds such as proteins, polyunsaturated fatty acids, polysaccharides, chlorophylls, carotenoids, vitamins and minerals. This work aims to study the impact of the 2 and 4 % microalga Chlorella vulgaris addition on the nutritional composition, bioactivity, structure and sensory profile of quark and cream cheese, both probiotic fermented products. Texture profile analysis and fundamental rheology measurements (oscillatory and stationary) were performed to evaluate the impact of C. vulgaris on the mechanical properties of the fresh cheese. The nutritional composition was evaluated using standard methods and bioactivity through the determination of total phenolic compounds and antioxidant capacity.1. C. vulgaris had an impact on the firmness of both cheeses. In general, the cheese with added C. vulgaris had a better nutritional profile, with an increase in protein content, content of Mg, P, S, Cu, Zn, Fe and Mn, and better bioactivity with an increase in the antioxidant activity. Sensory testing results were promising, especially for cream cheese. The enrichment of traditional foods such as fresh cheese with microalgae represents an interesting strategy to develop hybrid products (with protein from animal and vegetable sources), obtain innovative and more sustainable products, and improve their nutritional profile in terms of protein and mineral content and bioactivity.

A FT-NIR Process Analytical Technology Approach for Milk Renneting Control

The study proposes a process analytical technology (PAT) approach for the control of milk coagulation through near infrared spectroscopy (NIRS), computing multivariate statistical process control (MSPC) charts, based on principal component analysis (PCA). Reconstituted skimmed milk and commercial pasteurized skimmed milk were mixed at two different ratios (60:40 and 40:60). Each mix ratio was prepared in six replicates and used for coagulation trials, monitored by fundamental rheology, as a reference method, and NIRS by inserting a probe directly in the coagulation vat and collecting spectra at two different acquisition times, i.e., 60 s or 10 s. Furthermore, three failure coagulation trials were performed, deliberately changing temperature or rennet and CaCl2 concentration. The comparison with fundamental rheology results confirmed the effectiveness of NIRS to monitor milk renneting. The reduced spectral acquisition time (10 s) showed data highly correlated (r > 0.99) to those acquired with longer acquisition time. The developed decision trees, based on PC1 scores and T2 MSPC charts, confirmed the suitability of the proposed approach for the prediction of coagulation times and for the detection of possible failures. In conclusion, the work provides a robust but simple PAT approach to assist cheesemakers in monitoring the coagulation step in real-time.

Effect of physicochemical factors and use of milk powder on milk rennet-coagulation: Process understanding by near infrared spectroscopy and chemometrics

The effect of physicochemical factors and use of skim milk powder on milk rennet-coagulation was investigated combining near infrared (NIR) spectroscopic monitoring and Multivariate Curve Resolution - Alternating Least Squares (MCR-ALS). Coagulum formation has been studied by reference approaches (Formagraph and fundamental rheology) and with NIR spectroscopy on unaltered reconstituted milk samples, pasteurized samples, samples with calcium chloride addition and samples of reconstituted milk mixed with fresh milk. The MCR-ALS models successfully described the process evolution, explaining more than 99.9% of variance. The MCR-ALS profiles revealed to be significantly directly correlated with Formagraph and rheological data (p < 0.001) and allowed assessing the significant effect (p < 0.05) of the milk powder type on the coagulation occurrence and the non-significance (p > 0.05) of the CaCl2 concentration level added and the heat treatment applied. The MCR-ALS models calculated for the coagulation trials of pasteurized skimmed milk mixed with reconstituted milk samples highlighted shorter coagulation times with the increasing of reconstituted milk amount (from 4.3-6.6 min to 2–5 min). Profiles extracted from MCR-ALS models developed for a wide range of coagulation conditions proved to be suitable non-destructive, non-invasive and on-line tools to evaluate the rennet-induced coagulation of reconstituted milks.

Rheology Methods as a Tool to Study the Impact of Whey Powder on the Dough and Breadmaking Performance of Wheat Flour

Considering the nutritional value, whey is an excellent ingredient for the development of food products, in line with the concept of a circular economy for the reuse of industry by-products. The main objective of this work was to evaluate the impact of the whey addition on the rheology of wheat flour dough and breadmaking performance, using both empirical and fundamental methods. Different levels of commercial whey powder (0%, 12%, 16% and 20% w/w) were tested in a bread formulation previously optimized. Dough mixing tests were performed using Micro-doughLab and Consistograph equipment, to determine the water absorptions of different formulations and evaluate empirical rheology parameters related to mixing tolerances. Biaxial extension was applied by the Alveograph to simulate fermentation during the baking process. Fermented doughs were characterized in a Texturometer using penetration and extensibility tests, and by small amplitude oscillatory shear (SAOS) measurements, a fundamental rheology method, in a Rheometer applying frequency sweeps. Loaf volume and firmness were used to study the breadmaking quality. Despite a negative impact on the empirical rheology parameters of the dough and poorer baking results, the use of this by-product should be considered for nutritional and sustainability reasons. In addition, significant correlations (r2 &gt; 0.60) between the dough rheology parameters obtained from the empirical measurements were established. Changes in the gluten structure were not accurately detected by the SAOS measurements and Texture Profile Analysis of the doughs, and a correlation between fundamental and empirical measurements was not found. Consistograph or Micro-doughLab devices can be used to estimate bread firmness. Extensional tests in the Texturometer, using SMS/Kieffer Dough and Gluten Extensibility Rig, may predict loaf volume.

Effect of chemical oxidizers and enzymatic treatments on the rheology of dough prepared from five different wheat cultivars

The use of enzymes is attractive to the baking industry as an alternative to chemical oxidizers, as dough strengtheners, resulting in cleaner labels products (i.e., fewer ingredients). The quality parameters (proximate analysis, flour yield, gluten properties) and dough strength (i.e., empirical and fundamental rheology) of different wheat cultivars ranging in gluten strengths from weak (Harvest), intermediate (Lillian, CDC Plentiful and Stettler) and strong (Glenn) were analysed with the addition of chemical oxidizers (i.e., ascorbic acid, azodicarbonamide) or commercial enzymes (i.e., glucose oxidase and fungal xylanase). Glenn showed better quality attributes compared to the other cultivars, and responded well to additives, especially glucose oxidase which significantly improved dough strength. Glucose oxidase also improved the dough handling of weaker cultivars. Overall, the addition of enzymes resulted in comparable dough handling perhaps to chemical oxidizers when added at 50 or 100% of the permitted levels, but no differences were seen as a function of concentration.

Fundamental Rheology of Disperse Systems Based on Single-Particle Mechanics

A comprehensive review of the fundamental rheology of dilute disperse systems is presented. The exact rheological constitutive equations based on rigorous single-particle mechanics are discussed for a variety of disperse systems. The different types of inclusions (disperse phase) considered are: rigid-solid spherical particles with and without electric charge, rigid-porous spherical particles, non-rigid (soft) solid particles, liquid droplets with and without surfactant, bubbles with and without surfactant, capsules, core-shell particles, non-spherical solid particles, and ferromagnetic spherical and non-spherical particles. In general, the state of the art is good in terms of the theoretical development. However, more experimental work is needed to verify the theoretical models and to determine their range of validity. This is especially true for dispersions of porous particles, capsules, core-shell particles, and magnetic particles. The main limitation of the existing theoretical developments on the rheology of disperse systems is that the matrix fluid is generally assumed to be Newtonian in nature. Rigorous theoretical models for the rheology of disperse systems consisting of non-Newtonian fluid as the matrix phase are generally lacking, especially at arbitrary flow strengths.

Influence of a cationic polysaccharide on starch functionality

Fundamental rheology, differential scanning calorimetry and infrared spectroscopy have been used to evaluate the effect of a cationic polysaccharide, chitosan, on the gelatinization, gel formation and retrogradation of maize starch samples, under acidic aqueous conditions. Moderate acidic conditions (0.1molL−1 acetic acid) have shown a (slight) positive effect on starch gelatinization process and structure development. The presence of chitosan increased the DSC onset gelatinization temperature and also shifted the onset of the storage modulus increase to higher temperatures.Formation of the starch gel, mainly gelation of the leached-out amylose, is somehow hindered by the presence of the cationic polysaccharide and, therefore, the retrogradation of starch at very early stage can be delayed by addition of chitosan. However, long-term retrogradation was slightly increased. FTIR pectroscopy did not reveal any significant interaction between both polysaccharides what is in accordance with the observed rheological behavior. Small additions of chitosan to starch-rich systems may be a useful strategy to obtain new textures with novel phase transition behaviors.

Rheological and Thermo-mechanical Characterization of Starch – Protein Mixtures

Abstract The knowledge of the properties of model food systems is essential for designing new products with desired functionality. In order to address this issue, the present study was focused on mixtures consisting of 85% potato starch and 15% powdered eggs, gluten or soy protein concentrates. The nature of the proteins used in admixture with starch had a decisive role on the rheological properties of the batters and thermo-mechanical behavior of the doughs. The fundamental rheology tests indicated a solid like behavior with a strong cross-linked network for admixtures of starch with either gluten or soy, while starch - powdered egg batter showed a weak liquid like behavior. Observations made on gelling process highlighted the narrowed gelling temperatures domains for starch when mixed with proteins. Also protein addition determined the occurrence of a second inflection region in G‘curves associated with protein denaturation. The profile of the Mixolab curves varied with the type of protein, indicating low stability of the doughs and rather poor water holding capacity at kneading, especially in case of the powdered egg containing sample. The soy proteins exhibited the highest ability to retain water while heating the doughs. The interference of the protein products with starch granules swelling and gelatinization at thermal treatment depended on their composition, structural properties and thermal stability. The highest stability at 90°C was registered for the sample with soy protein, whereas the gluten containing mixture exhibited the lowest tendency of starch retrogradation.

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 360min 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.

Influence of jambolan (Syzygium cumini) and xanthan gum incorporation on the physicochemical, antioxidant and sensory properties of gluten‐free eggless rice muffins

SummaryThis study was undertaken to prepare antioxidant‐rich gluten‐free eggless muffins from rice flour blended with varying amounts of jambolan fruit pulp (JFP) and xanthan gum (XG). The batters were evaluated for fundamental rheology, while muffins were analysed for physicochemical (colour, volume, water activity, total phenolic and flavonoid content), texture and sensory properties. The incorporation of JFP and XG increased batter viscoelasticity (increased G′ and G″ while decreased tan δ). JFP incorporation increased greenness (lower a* value), cohesiveness, resilience, water activity (aw), total phenolic content, total flavonoid content, DPPH and ABTS inhibition of the muffins. Further, XG improved muffin quality characteristics (appearance, specific volume and resilience). Sensory analyses revealed that JFP incorporation improved the consumer acceptability of the muffins.

4th Iberian Meeting on Rheology. Fundamental and Applied Rheology (IBERO 2013)

4th Iberian Meeting on Rheology. Fundamental and Applied Rheology (IBERO 2013)

Joint Symposium of the German Rheological Society and the Polymer Processing Society (PPS-29) Fundamental and Applied Rheology

Joint Symposium of the German Rheological Society and the Polymer Processing Society (PPS-29) Fundamental and Applied Rheology

Dough microstructure: Novel analysis by quantification using confocal laser scanning microscopy

The effect and the correlation of water addition to flour on the microstructure and viscoelastic properties of wheat flour dough were investigated using confocal laser scanning microscopy and a spectrum of rheological methods. Dough with water addition in the range of 52.5–70.0 g water 100 g −1 flour was investigated using a stickiness test, uniaxial elongation test, and fundamental rheology like small amplitude oscillatory shear measurement and a creep recovery test. A method for quantifying the microstructure of dough protein gained by CLSM was established with image processing and analysis. The complex shear modulus decreased rapidly with water addition due to the plasticization effect of water molecules and increased mobility in the continuous phases. Elastic behavior, determined as loss factor tan δ and relative elastic part J el decreased. Rheological tests showed high linear correlations with each other (r of |0.66|–|0.98|). Image analysis measurements (average size, area fraction, perimeter, circularity, and fractal dimension) showed high linear correlations (r of |0.66|–|0.85|) with water addition and rheological attributes like the complex shear modulus (r = 0.85) and J el (r = 0.86). CLSM in combination with image processing and analyzing has proven to be an applicable and powerful tool for examining and quantifying dough protein microstructure. Hence, it was possible to prove the dependency of rheology on the microstructure of dough.

Annual Meeting of the German Rheological Society: Recent Trends in Fundamental and Applied Rheology

Annual Meeting of the German Rheological Society: Recent Trends in Fundamental and Applied Rheology

Identification of lactic acid bacteria isolated from oat sourdoughs and investigation into their potential for the improvement of oat bread quality

The use of sourdough in wheat and rye breads has been extensively studied; however, little is known about its potential effect when baking oat bread. Consequently, the impact of sourdough on oat bread quality was investigated. Two different sourdoughs were prepared from wholegrain oat flour without the addition of starter cultures, by continuous propagation at 28 (SD 28) or 37 °C (SD 37) until the composition of the lactic acid bacteria remained stable. The dominant LAB were identified by sequence analysis of the 16S rDNA isolated from pure cultures. LAB from SD 28 belonged to the species Leuconostoc argentinum, Pedicoccus pentosaceus and Weissella cibaria, while Lactobacillus coryniformis dominated SD 37. The isolated LAB were further used as starter cultures for the production of oat sourdoughs. Fundamental rheology revealed softening of the sourdoughs compared to non-acidified and chemically acidified controls, which could not be attributed to proteolytic activity. Incorporation of oat sourdough into an oat bread recipe resulted in significantly increased loaf-specific volume as well as improved texture, independent of addition level or sourdough type. Overall, the results of this study show that sourdoughs containing lactic acid bacteria isolated from oats have the potential to enhance oat bread quality.

Effect of protease treatment on the baking quality of brown rice bread: From textural and rheological properties to biochemistry and microstructure

In this study, protease treatment of brown rice (BR) batters was investigated in order to evaluate its impact on the textural and baking properties of BR bread. The enzymatic treatment improved bread quality by significantly increasing specific volume ( p < 0.05), while decreasing crumb hardness and chewiness ( p < 0.05). Fundamental rheology and viscometry of batters revealed that protein hydrolysis induced lower complex modulus and initial viscosity, while phase angle was unaffected. Flour pasting properties were also affected, with a significant decrease in paste viscosity and breakdown ( p < 0.05). Protein analysis of batters revealed that the enzymatic treatment induced the release of low molecular weight proteins from macromolecular protein complexes. In conclusion, a lower resistance to deformation of batters during proofing and in the early stages of baking as well as the preserved batter elasticity and the increased paste stability positively affected the breadmaking performance.

Fundamental studies on the reduction of salt on dough and bread characteristics

The impact of salt reduction on a wide range of dough and bread characteristics is addressed in this study. The effect of an incremental reduction of salt, from current usage levels (1.2%) to 0.6%, 0.3% and 0% addition, was considered from a fundamental and practical perspective. Empirical and fundamental rheology, bread-making performance and descriptive sensory evaluation were employed to gain practical insight into the viability of salt reduction in wheat dough and bread. Decreasing salt addition reduced the dough resistance to extension, extensibility and complex modulus without affecting the ratio of liquid to solid behaviour, thereby indicating that no major structural changes take place as a result of salt reduction. Changes in gas holding capabilities of doughs with reduced salt were observed, however not affecting the final bread quality, e.g. specific volume, bake-loss or moisture-loss. Omission of salt resulted in uneven crumb structure and high crumb hardness on day 5 post-baking, however these effects were not present when salt was included in the formulation, even at low levels of addition, i.e. 0.6% or 0.3%. Breads were more strongly affected by age than by level of salt addition in the sensorial evaluation. Overall, breads produced with 0.3% and 0.6% salt were found to be comparable to the control (1.2% salt) in terms of dough rheology, baking quality characteristics and sensory attributes.

Microstructure, fundamental rheology and baking characteristics of batters and breads from different gluten-free flours treated with a microbial transglutaminase

Gluten is a fundamental component for the overall quality and structure of breads. The replacement of the gluten network in the development of gluten-free cereal products is a challenging task for the cereal technologist. The functionality of proteins from gluten-free flours could be modified in order to improve their baking characteristics by promoting protein networks. Transglutaminase (TGase) has been successfully used in food systems to promote protein cross-linking. In this study, TGase was investigated for network forming potential on flours from six different gluten-free cereals (brown rice, buckwheat, corn, oat, sorghum and teff) used in breadmaking. TGase was added at 0, 1 or 10 U/g of proteins present in the recipe. The effect of TGase on batters and breads was evaluated by fundamental rheological tests, Texture Profile Analysis and standard baking tests. Three-dimensional elaborations of Confocal Laser Scanning Microscopy (CLSM) images were performed on both batters and breads to evaluate the influence of TGase on microstructure. Fundamental rheological tests showed a significant increase in the pseudoplastic behaviour of buckwheat and brown rice batters when 10 U of TGase were used. The resulting buckwheat and brown rice breads showed improved baking characteristics as well as overall macroscopic appearance. Three-dimensional CLSM image elaborations confirmed the formation of protein complexes by TGase action. On the other side, TGase showed negative effects on corn flour as its application was detrimental for the elastic properties of the batters. Nevertheless, the resulting breads showed significant improvements in terms of increased specific volume and decreased crumb hardness and chewiness. Under the conditions of this study, no effects of TGase could be observed on breads from oat, sorghum or teff. Overall, the results of this study show that TGase can be successfully applied to gluten-free flours to improve their breadmaking potentials by promoting network formation. However, the protein source is a key element determining the impact of the enzyme.

Impact of Industrial Dough Processing on Structure: A Rheology, Nuclear Magnetic Resonance, and Electron Microscopy Study

ABSTRACTDough processing is an important factor determining the quality of bread. The most important mechanical steps in industrial dough processing are kneading, extrusion, and molding. In all of these processing steps, considerable changes in the structure and properties of the dough can occur. On a laboratory‐scale level, these (structural) effects are well characterized but, so far, no systematic study has been performed at the level of a large‐scale industrial dough processing line. The molecular and microstructural changes that can take place during industrial dough processing were studied with the help of nuclear magnetic resonance (NMR), fundamental rheology, and scanning electron microscopy (SEM). After the kneading step, the dough shows a well‐developed gluten network with a homogeneous dispersion of starch particles (at optimum kneading time). After the extrusion step (a sheeting procedure), the structure of the dough becomes coarser and the dough gluten network is oriented and partially disrupted. This is accompanied with an increase in both rheological stress and water mobility. After molding, the network structure is restored and both the rheological stress and the mobility of water decrease. These findings provide a novel microstructurally‐lead approach to make recommendations for optimization of industrial dough processing lines.