Submitted to: Journal of Cereal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 8, 2010
Publication Date: November 1, 2010
Citation: Schober, T.J., Moreau, R.A., Bean, S. and Boyle, D.L. 2010. Removal of surfac lipids improves the functionality of commercial zein in viscoelastic zein-starch dough for gluten-free breadmaking. Journal of Cereal Science. 52(3):417-425. Interpretive Summary: Celiac disease is a condition, in which the human immune system erroneously attacks the intestine when gluten is ingested, causing, amongst many other symptoms, severe diarrhea and malabsorption. Its occurrence has been largely underestimated in the United States and world-wide, and recent studies suggest that 2-3 million Americans are affected. All gluten containing cereals have to be avoided by celiac patients, including wheat, rye, barley and ancient relatives of wheat like spelt wheat, emmer, and einkorn. Bread for these people has to be made from gluten-free grains like corn (maize), rice, sorghum, or isolated starches, and is frequently of poor quality when compared to wheat bread. The present study describes an important step in improving gluten-free bread. Using corn proteins (zein), a wheat-like dough can be produced. The present study is a follow-up on a previous one (Schober et al., 2008; Journal of Cereal Science 48, 755-767). Previously, zein dough lacked strength and produced flat rolls, limiting its use. In the present study, we found that an additional defatting step helps in making zein dough much more similar to wheat dough, and in producing hearth-type rolls that closely resemble wheat rolls. Zein is currently a by-product from corn wet milling and fuel-ethanol production. The results of the present study might help in supplying celiacs with better bread and in making the bio-fuel process more economical.
Technical Abstract: Maize prolamin (zein), together with starch, hydroxypropyl methylcellulose, sugar, salt, yeast and water can form wheat-like cohesive, extensible, viscoelastic dough when mixed above room temperature (e.g. 40 °C). This dough is capable of holding gas. However, it is excessively extensible, and when used for hearth-type rolls, it tends to become flat. Bench-scale defatting of zein with chloroform at room temperature significantly (P<0.05) improved volume (4.5 ml/g vs. 3.3 ml/g) and shape of the rolls (width-to-height 2.0 vs.3.9). The total lipid content determined by accelerated solvent extraction (100 °C, 1000 psi, chloroform), however, only sank from 8.0 to 6.6% due to this bench-scale defatting. Staining experiments with Naphthol Blue Black suggested that bench-scale defatting removed surface-lipids from the zein particles, and thus facilitated their aggregation. Aggregation experiments with zein and water at 40 °C, and laser scanning confocal microscopy with zein-starch dough confirmed that zein particles aggregated more easily when surface-defatted. Dynamic oscillatory temperature sweeps demonstrated that surface-defatting lowered the temperature, at which protein cross-linking occurred by '2 °C. This research can help to produce superior gluten-free bread and could also possibly contribute to the better understanding of wheat dough.