Large-Deformation Properties of Wheat Flour and Gluten Dough

Keywords: Wheat, gluten protein, bread, puff pastry, flour dough, gluten dough,rheology,uniaxialextension, biaxial extension, fracture.Rheologicaland fracture properties of flour and glutendoughsfrom eight wheat cultivars were studied and related to gluten protein composition and baking performance in bread and puff pastry. For bothuniaxialand biaxial extension flour dough showed a more than proportional increase of stress with increasing strain, a phenomenon called strain hardening. Inuniaxialextension (i) stresses at a certain strain were higher and (ii) stress was less dependent on strain rate than in biaxial extension. Stress at a certain strain and strain hardening depended much stronger on the type of deformation for gluten than for flour dough. These findings are consistent with published data on birefringence of gluten and show that orientation of structure elements inelongationalflow plays an important role in flour and gluten dough.For flour dough fracture stress and strain increased with increasing strain rate. At higher strain rates and lower temperatures fracture strains hardly differed between different flourdoughsno matter the protein content or composition. At lower strain rates and higher temperatures the smallest fracture strains were found for flourdoughswith the lowestglutenincontents and/or the lowest protein contents. We concluded that the strain rate and temperature-dependency of the fracture strain is a very important factor to relate to protein composition. Fracture stresses were much higher for gluten than for flour dough, while fracture strains were in the same range or higher. Contrary to flour dough, the smallest fracture strains were found for glutens with the largestglutenincontents.Puff pastry volume was positively correlated with strain hardening and negatively with thestrainrate-dependency of the stress and the strain rate and temperature-dependency of the fracture stress and strain. For bread it were thedoughswith intermediate dough strength that gave the highest loaf volume, while loaf volumes of flours with high dough strength (i.e. high stress-level and high strain hardening coefficient) gave intermediate loaf volumes. We concluded that a high internal stress limits the deformability of dough films between gas cells and with that of the loaf volume that can be obtained

A fast and simple method for quantitative determination of fat-derived medium and low-volatile compounds in cheese

Cheese flavour is a mixture of many (volatile) compounds, mostly formed during ripening. The current method was developed to qualify and quantify fat-derived compounds in cheese. Cheese samples were extracted with acetonitrile, which led to a concentrated solution of potential favour compounds, mainly derived from milk fat. The solution was virtually free from triglycerides, protein and salt from the cheese matrix. Therefore, such an extract could be analysed directly by gas chromatography/mass spectroscopy (GC/MS). In the samples of the three cheese varieties analysed, 61 different compounds were identified, including 23 fatty acids, 14 lactones, 9 esters, 5 ketones, 10 alcohols, and several miscellaneous compounds. Furthermore, most compounds could be quantified by determining their distribution coefficients and thus correcting for their loss during extraction. This method was shown to be suitable for both qualitative and quantitative analysis of medium and low-volatile compounds. (C) 2003 Elsevier Science Ltd. All rights reserved

Production of fat-derived (flavour) compounds during the ripening of Gouda cheese

Fat-derived flavour compounds in four different batches of Gouda cheese were monitored over 2 years of ripening. The total free fatty acid (FFA) concentrations increased from 200–400 to 700–1200 mg kg–1 dry matter, in a fairly linear manner. Long-chain FFAs were predominant in the curds, but relatively more short and intermediate chain fatty acids were released during ripening. The production of d-lactones was rapid initially, but reached a plateau at 55 mg kg–1 dry matter in about 20 weeks. The production of ¿-lactones was slower and also decreased, but was noticeable over a longer time, giving 5.5 mg kg–1 dry matter in 90 weeks. Ethyl ester formation varied substantially. Ketone levels increased only very slightly during ripening; long chain alcohols and aldehydes were not found. Some individual FFAs and lactones exceeded reported flavour thresholds, and are expected to influence the flavour of Gouda cheese

On the relationship between large-deformation properties of wheat flour dough and baking quality

Baking performance for bread and puff pastry was tested for Six European and two Canadian wheat cultivars and related to the rheological and fracture properties in uniaxial extension of optimally mixed flour-water doughs and doughs to which a mix of bakery additives was added. Extensive baking tests were performed as a function of water addition for puff pastry and as a function of water addition and mixing time for bread. For optimum baking performance, puff pastry doughs required lower water additions than bread doughs. Baking performance of the flours differed for the two products. For puff pastry, higher volumes were obtained per gram of flour than for bread. Puff pastry volume was positively correlated with optimum bread dough mixing time, while bread volume was not. Instead, bread volume was positively correlated with gluten protein content

Large-deformation properties of wheat dough in uni- and biaxial extension. Part I. Flour dough

Rheological and fracture properties of optimally mixed flour doughs from three wheat cultivars which perform differently in cereal products were studied in uniaxial and biaxial extension. Doughs were also tested in small angle sinusoidal oscillation. In accordance with previously published results the linear region was found to be very small. The rheological properties at small deformations hardly depended on the cultivar. A higher water content of the dough resulted in a lower value for the storage modulus and a slightly higher value for tan ?. For both uniaxial and biaxial extension a more than proportional increase in stress was found with increasing strain, a phenomenon called strain hardening. In uniaxial extension (i) stresses at a certain strain were higher and (ii) the stress was less dependent on the strain rate than in biaxial extension. This indicates that in elongational flow orientational effects are of large importance for the mechanical properties of flour dough. This conclusion is consistent with published data on birefringence of stretched gluten. Fracture stress and strain increased with increasing deformation rate. The observed time-dependency of fracture properties can best be explained by inefficient transport of energy to the crack tip. Presumably, this is caused by energy dissipation due to inhomogeneous deformation because of friction between structural elements, e.g. between dispersed particles and the network. Differences in the rheological properties at large deformations between the cultivars were observed with respect to (i) stress, (ii) strain hardening, (iii) strain rate dependency of the stress, (iv) fracture properties and (v) the stress difference between uniaxial and biaxial extension. keyword(s) Dough rheology, Strain hardening, Uniaxial extension, Biaxial extension, Fracture properties

The formation mechanism of lactones in Gouda cheese

Lactones are fat-derived aroma compounds, but the formation mechanism of these compounds during ripening of Gouda cheese is unknown. Both enzymatic and chemical formation pathways were investigated in this study. Lactone formation from milk triglycerides or free fatty acids by lactic acid bacteria enzymatic activity was not observed. Instead, the mechanism of the lactone formation in cheese was a one-step, non-enzymatic reaction, where a hydroxy fatty acid, esterified in a triglyceride undergoes trans-esterification to release the lactone directly. The lactone reaction potential was determined for all major ¿- and ¿-lactones by controlled heating of the fat. The chemical formation of lactones was temperature-dependent and the Arrhenius parameters of the formation reaction were estimated for each of the lactones. The kinetics of the reaction were first-order, and could be used to explain the formation of lactones in ripening Gouda cheese up to about 40 week

On the relationship between gluten protein composition of wheat flours and large-deformation properties of their doughs

Six European and two Canadian wheat cultivars selected according to their different performance in baked cereal products. The gluten protein composition of the respective flours was studied and related to the rheological and fracture properties of optimally mixed flour doughs tested in uniaxial extension. Water addition required for optimum dough development was positively correlated with gluten protein content, indicating that all glutens required similar amounts of water for proper hydration. Both water addition and gluten protein content were positively correlated with the fracture strain. Mixing time required for optimum dough development was correlated with several stress-related dough properties: positively with the stress at a large strain and strain hardening and negatively with the strain rate-dependency of the stress. These stress-related dough properties were correlated with differences in the amount and the size-distribution of the gluten proteins. A positive correlation was found the stress at large strain and the percentage of polymeric protein of large size (UEP+P1) and a negative correlation between the strain rate-dependency of the stress and the percentage of high molecular weight glutenin subunits on total protein. These findings are consistent with the known strong dependence of rheological properties on molecular weight and molecular weight distribution for polymers in general. The effect of temperature on the large-deformation properties of flour and gluten dough was studied for three cultivars that were considered representative for the whole set. The fracture properties of flour dough strongly depended on strain rate and temperature. At higher strain rates and lower temperatures, fracture strains scarcely differed between the flour doughs no matter the protein content or composition. On the other hand at lower strain rates and higher temperatures the smallest fracture strain was found for dough of flour with the lowest glutenin content and/or the lowest protein content. In contrast to the flour doughs, for gluten–water mixtures (gluten doughs) the fracture strain was largely independent of strain rate and temperature. The smallest fracture strain was found for the gluten dough with the highest glutenin content. Thus, the behaviours of flour and gluten doughs with respect to protein composition, strain rate and temperature effect on fracture strain clearly are different. The differences observed in large deformation and fracture properties are most likely due to the large differences in starch and gluten protein content between flour and gluten doughs