Ingrid De Leyn

Rheological properties of wheat flour dough and the relationship with bread volume. I: Creep-recovery measurements

ABSTRACT The rheological properties of 17 pure European wheat cultivars were analyzed and evaluated in relation to the bread volume. Rheological testing included two empirical rheological methods, farinograph and alveograph, and more fundamental creep-recovery experiments at shear stresses of 100 and 250 Pa. Principal component analysis on the farinograph and alveograph results showed that a wide range of rheological properties was present among the wheat cultivars. Correlation analysis pointed out that creep-recovery parameters showed significant correlations with protein content, Zeleny sedimentation value, farinograph water absorption, alveograph extensibility, and bread volume. Among the rheological parameters, maximum recovery strain at a shear stress of 250 Pa showed the highest significant correlation with the bread volume (r = 0.790**). Variables were combined to predict the bread volume by multiple linear regression. A combination of protein content, farinograph water absorption, and alveograph P...

Rheological Properties of Wheat Flour Dough and Their Relationship with Bread Volume. II. Dynamic Oscillation Measurements

ABSTRACT The rheological properties of 17 pure European wheat cultivars were analyzed and evaluated in relation to the bread volume. Rheological testing included two empirical rheological methods, farinograph and alveograph, in addition to more fundamental rheological methods, specifically the creep-recovery and dynamic oscillation measurements. The four rheological methods revealed large differences in dough rheological properties among the 17 wheat cultivars. Phase angle δ and the moduli were strongly correlated. The dynamic oscillation parameters also correlated significantly with protein content, Zeleny sedimentation value, damaged starch content, and farinograph water absorption. A nonlinear relationship (power) between the maximum creep or recovery strain and the dynamic moduli was found for both shear stresses (100 and 250 Pa). Phase angle δ showed a positive relationship with the maximum creep or recovery strain. The dynamic oscillation parameters could be related to the bread volume. Phase angle ...

Composition, Granular Structure, and Pasting Properties of Native Starch Extracted from Plectranthus edulis (Oromo dinich) Tubers

Chemical composition, granular morphology and pasting properties of native starch extracted from tubers of Plectranthus edulis were analyzed. Starch was extracted from tubers of 6 accessions collected from 4 different areas in Ethiopia. Particle size analysis (PSA) and cryo-scanning electron microscope (cryo-SEM) imaging were used to examine the granular morphology and visualize the starch paste, respectively. Pasting properties, water absorption, and gelation capacity were compared. A wide range was found for the amylose (14.2% to 23.9%), calcium (216 to 599), potassium (131 to 878), and phosphorus (1337 to 2090) contents (parts per million per dry matter). PSA showed a bimodal distribution containing small spherical (14.6 μm) and large ellipse-shaped (190.4 μm) granules. Major differences were found for the pasting with peak viscosities differing from 3184 to 7312 mPa⋅s. Starch from accessions Chencha and Inuka showed a difference in packing density as clearly seen through cryo-SEM image at 75% of the peak viscosity (PV), and the granular integrity was mainly responsible for the significant difference in their PV and breakdown. Principal component analysis revealed 2 distinct groups: native starch extracted from accessions at the Wolayta zone (Inuka, Lofua, and Chenqoua) and other accessions (Jarmet, Arjo white, and Chencha). The study revealed the potential of P. edulis starch for its application in food industries. However, the inherent variation due to environmental conditions on physicochemical properties of the starch needs further investigation. PRACTICAL APPLICATION Plectranthus edulis is cultivated in considerable amounts throughout Ethiopia, which makes it a valuable starch source. Due to its low tendency to retrograde, it could be applied in food industry as an equivalent for the current starch sources. Moreover, the low amylose content makes it preferable for an application in refrigerated foods as this unique quality trait prevents syneresis in end products during storage. Based on the significantly higher pasting temperature of the studied P. edulis starch extracts, it can form an alternative for potato starch, which is less suitable for its use in pasteurized foods.