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

CRISPR-knockout of β-kafirin in sorghum does not recapitulate the grain quality of natural mutants

When gene editing was applied to knockout beta-kafirin, there was a compensatory increase of gamma-kafirin which does not occur in domesticated null varieties, so enhanced grain quality was not achieved. Sorghum bicolor is an important animal feedstock cereal crop throughout Australia and the southern United States, where its use as a food product is limited by issues with low calorific and nutritive value. Qualities such as reduced digestibility and low essential amino acid content are directly attributed to the kafirin grain storage proteins, the major components of protein bodies within the endosperm. Specifically, the β- and γ-kafirins have few protease cleavage sites and high levels of cysteine residues which lead to a highly cross-linked shell of intra- and inter-molecular disulphide linkages that encapsulate the more digestible α- and δ-kafirins in the core of the protein bodies. Naturally occurring β-kafirin mutants exist and are known to have improved grain quality, with enhanced protein contents and digestibility, traits which are often attributed to the lack of this cysteine-rich kafirin in the mature grain. However, when CRISPR/Cas9 editing was used to create β-kafirin knockout lines, there was no improvement to grain quality in the Tx430 background, although they did have unique protein composition and changes to protein body morphology in the vitreous endosperm. One explanation of the divergence in quality traits found the lines lacking β-kafirin are due to a drastic increase of γ-kafirin which was only found in the gene edited lines. This study highlights that in some germplasm, there is a level of redundancy between the peripheral kafirins, and that improvement of grain protein digestibility cannot be achieved by simply removing the β-kafirin protein in all genetic backgrounds.

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

The substitution of wheat gluten in the food industry is a relevant research area because the only known treatment for celiac disease is abstinence from this protein complex. The use of gluten-free cereals in dough systems has demonstrated that the viscoelastic properties of gluten cannot be achieved without the modification of the protein fraction. The quality of the final product is determined by the ability of the modification to form a matrix similar to that of gluten and to reach this, different methods have been proposed and tested. These procedures can be classified into four main types: chemical, enzymatic, physical, and genetic. This article provides a comprehensive review of the most recent research done in protein modification of cereal and pseudocereals for gluten substitution. The reported effects and methodologies for studying the changes made with each type of modification are described; also, some opportunity areas for future works regarding the study of the effect of protein modifications on gluten-free products are presented.

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

Dough fermentation with lactic acid bacteria has been extensively studied due to the associated health benefits and its effects on physical and rheology parameters in dough and bread. However, most of the studies rely on long fermentation times. The aim of this study is to evaluate the effect of short fermentation times (0 to 8 h) with Lactobacillus paracasei in rheology, physical and chemical properties on cassava dough and biscuits. Both storage modulus and loss modulus decreased as the fermentation times increased, down to 54,206.67 ± 13,348 and 17,453.89 ± 3691 Pa, respectively. Fermentation with L. paracasei influenced biscuit’s hardness and chemical properties, and gas cell sizes were increased notably. These results suggest that short fermentation times could be used to improve dough’s rheological characteristics.