Impact of different isolation procedures on the functionality of zein and kafirin |
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Authors: | Tilman J Schober Scott R Bean Michael Tilley Brennan M Smith Brian P Ioerger |
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Institution: | Center for Grain and Animal Health Research, Agricultural Research Service, U.S. Department of Agriculture (USDA), 1515 College Avenue, Manhattan, KS 66502, USA |
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Abstract: | Commercial corn prolamin (zein) aggregates in water at elevated temperatures into an extensible, viscoelastic gluten-like substance. This specific functionality of zein can be used in the production of gluten-free bread from true dough systems and not from batters. The present study examined laboratory-scale isolation of such functional zein from dry milled corn. RP-HPLC indicated that successful isolation procedures resulted in relatively pure α-zeins, with a maximum ratio of (β + γ)/α-zeins of about 10%. In the present study, such functional zeins were obtained by using 70% ethanol as the extractant, without added alkali or reducing agent in the main extraction step. In contrast, films could be cast from a wider range of zein isolates, also with higher ratios of (β + γ)/α-zeins. Isolation of the analogous prolamin (kafirin) from dry milled sorghum required a more hydrophobic extractant such as 83% isopropanol to achieve partial functionality. Such kafirin was able to aggregate in warm water, preferably when a reducing agent was added; however, it quickly became firm and lost its extensibility. The present study suggests that hydrophobic interactions rather than disulfide bonds are the key to gluten-like functionality of zein and kafirin. |
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Keywords: | Zein Kafirin Viscoelasticity Gluten |
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