Document Type
Thesis - University Access Only
Award Date
2005
Degree Name
Master of Science (MS)
Department / School
Chemistry and Biochemistry
Abstract
Zein has been known since it was first identified in 1821 by infusing Indian corn with water. Zein constitutes about one-half of the protein in com and is composed of a mixture of proteins differing in molecular size, solubility, and charge. Four distinct types of zein were classified: a-, P-, y- and 8-zein. a-Zein is the most abundant type (70%. w/w), P-zein accounts for about 20% of the total, and y- and 8-zeins make up the remaining 10%. Because of zein's special properties including grease and microbial resistance, resistance to oxygen and carbon dioxide transport, ability to form films and biodegradability, a wide range of applications have been explored such as coatings, fibers. ink, molded articles. adhesives etc. Its high price ($10 to $44/kg) has hindered zein’s industrial uses. Previous studies on zein extraction concluded that a cheaper source of zein is necessary to reduce its price. Wolf and Lawton's (1997) work showed that Distillers Dried Grains (DOG) is the cheapest zein source. Based upon its unacceptable fermented flavor and the deficiency in lysine, DOG has no current industrial application. Its main use is to feed cattle. Previous trials to extract zein by aqueous ethanol plus Dithiothreitol (OTT) from DOG achieved a low yield (3.2-6.6%). The purpose of this study is to optimize zein's extraction conditions from DOG and characterize extracted proteins by spectroscopic and chromatographic techniques. Statistical analysis of aqueous ethanol extracted crude zein yield showed that the optimal crude zein extraction condition is 50% ethanol at 60° C plus 0.1 % OTT. Crude zein extracted under this condition showed up to a 230% increase over published values reported by Wolf and Lawton (1997). a-Zein was recovered from extracted crude zein, and showed that crude zein extracted by 50% ethanol at 60" C plus 0.1 % OTT from DOG achieved the highest a-zein recovery yield (11.8%). Silver-stained SOS-PAGE showed that a-zein, ~- or y- zein, and 8-zein were extracted from DOG by the aqueous ethanol plus OTT system and that the ICN commercial zein contains a- and 8- zein only. Matrix Assisted Laser Desorption Ionization - Time of Flight Mass Spectroscopy (MA LD 1-TOF MS) was successfully used to characterize a-zein. The combination of HPLC and MA LO 1-TOF MS complement each other in a-zein composition characterization, and showed that a-zein recovered from DOG has different a-zein composition from the ICN zein. Water holding capacity of crude zein can be used to determine quality of extracted zein when no other analytical instruments are available. Cast film made from extracted crude zein from DOG showed that although the composition of a-zein recovered from DOG is different from that of ICN zein, it still has film forming property.
Library of Congress Subject Headings
Distilling industries -- By-products
Corn products
Extraction (Chemistry)
Format
application/pdf
Number of Pages
82
Publisher
South Dakota State University
Recommended Citation
Xiang, Feng, "Processing and Characterization of Zein from Distillers' Dried Grains" (2005). Electronic Theses and Dissertations. 1224.
https://openprairie.sdstate.edu/etd2/1224