Modification of zein dough functionality using kafirin as a coprotein

Authors: NCUBE, MPHOKUHLE - UNIVERSITY OF PRETORIA; TAYLOR, JANET - UNIVERSITY OF PRETORIA; Bean, Scott; IOERGER, BRIAN; TAYLOR, JOHN - UNIVERSITY OF PRETORIA

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2021
Publication Date: 12/7/2021
Citation: Ncube, M.B., Taylor, J., Bean, S.R., Ioerger, B.P., Taylor, J.R. 2021. Modification of zein dough functionality using kafirin as a coprotein. Food Chemistry. 373. Article 131547. https://doi.org/10.1016/j.foodchem.2021.131547.
DOI: https://doi.org/10.1016/j.foodchem.2021.131547

Interpretive Summary: There is increasing interest in use of sorghum flour in food products. However, sorghum proteins do not have the ability to form a dough which limits the use of sorghum flour in baked food products. This research investigated the use of isolated sorghum proteins added to commercially available corn proteins to improve the ability of the two proteins to form wheat-like dough. Addition of isolated sorghum proteins to the commercial corn proteins increased elastic dough properties similar to gluten. Furthermore, sorghum protein inclusion with the corn proteins also increased the strength of starch-based doughs, though dough strength was only 60% that of gluten-based dough. This research demonstrates that adding sorghum proteins to commercially available corn proteins improves functionality in dough systems and provides avenues to increasing utilization of sorghum and improving baked products made with sorghum components.

Technical Abstract: Coproteins can improve the visco-elasticity of zein (maize prolamin). Here, kafirin, sorghum prolamin, was investigated as a coprotein for zein. Regular kafirin and kafirins from waxy and high protein digestibility (HD) sorghum crosses were studied. Waxy-HD kafirin was of smaller molecular size, low in ß-kafirin with high surface hydrophobicity. Kafirin addition to zein increased visco-elastic mass elasticity up to ˜50% stress-recovery, similar to gluten. Waxy-HD kafirin gave the highest elasticity, possibly due to its hydrophobicity. Kafirin inclusion at 2:8 parts zein also increased the strength of starch-based doughs. Maximum strength was, however, only 60% that of gluten-based dough. Kafirin from regular sorghum gave the highest strength, probably because of its greater three-dimensional disulphide-bonded polymerisation. Confocal laser scanning microscopy showed that the zein and kafirin formed fairly linear fibrils in stretched doughs, indicating excellent compatibility between the proteins. Future research should establish how kafirin-zein copolymer performs in non-wheat flour products.