Transgenic sorghum with suppressed synthesis of kafirin subclasses: Effects on flour and dough rheological characteristics

Abstract

Arising from work showing that conventionally bred high protein digestibility sorghum types have improved flour and dough functionality, the flour and dough properties of transgenic biofortified sorghum lines with increased protein digestibility and high lysine content (TG-HD) resulting from suppressed synthesis of several kafirin subclasses, especially the cysteine-rich γkafirin, were studied. TG-HD sorghums had higher flour water solubility at 30 o C (p <0.05) and much higher paste viscosity (41% higher) than their null controls (NC). TG-HD doughs were twice as strong as their NC and dynamic rheological analysis indicated that the TG doughs were somewhat more elastic up to 90 o C. CLSM of doughs and pastes indicated that TG-HD had a less compact endosperm protein matrix surround the starch compared to their NC. The improved flour and dough functional properties of the TG-HD sorghums seem to be caused by reduced endosperm compactness resulting from suppression of synthesis of several kafirin subclasses which modifies protein body and protein matrix structure, and to improved protein-starch interaction through hydrogen bonding specifically caused by reduction in the level of the hydrophobic γ-kafirin. The improved flour functionality of these transgenic biofortified sorghums can increase their commercial utility by complementing their improved nutritional quality.

Effect of Short Fermentation Times with Lactobacillus paracasei in Rheological, Physical and Chemical Composition Parameters in Cassava Dough and Biscuits

“…The decline of τ indicates that dough opposes less resistance as the fermentation time increases, meaning that doughs start exhibiting a decreased elastic behavior compared to control. This has been discussed in another study where it was found that sourdoughs have lower shear stress values compared to regular doughs [27].…”

Methods for the Modification and Evaluation of Cereal Proteins for the Substitution of Wheat Gluten in Dough Systems

“…Several studies have opted to use Confocal Laser Scanning Microscopy (CLSM) as an alternative to SEM; this technique uses the emitted fluorophores of a sample after a laser scan to generate the image [ 112 ]. Taylor et al used this technique to show the fibril formation of zein and kafirin resins, while Elhassan et al used it to investigate the internal structure of kafirin doughs, an unavailable application for SEM [ 63 , 71 ]. Since both microscopies techniques can study the microstructure of a sample, the election of equipment would depend on the information needed.…”

“…The rheometer is used to comprehend the dough rheological effects of a modification on final products [ 67 ]. This equipment works by applying a rotational or sinusoidal (oscillatory) shear deformation on a sample and measuring the resulting stress response, which can be used to study the viscoelastic moduli (G’ and G”) of gluten-free bread [ 67 , 69 , 71 , 115 ]. Since both techniques obtain the same information, the election would depend on the type of material studied.…”

“…The former predicts how much a material will deform when stress is applied, and the latter, how fast the material will flow [ 117 ]. In breadmaking, softer doughs have less elastic behavior (lower G’), since higher G” would indicate a more viscous behavior, and hence a less ordered dough structure [ 71 ].…”

“…To the knowledge of the authors, in recent years, the only work done where the modification fits this criterion is Elhassan et al’s research with transgenic sorghum, where γ-kafirin expression was suppressed. These genetically modified seeds formed stronger doughs than null controls, as evidenced by the higher maximum force showed during compression tests (up to a 95.9% increase) [ 71 ]. The study found that the suppression of kafirin subclasses resulted in a less dense endosperm with modified protein bodies and improved protein-starch interactions through hydrogen bonding.…”