|Seabourn, Bradford - Brad|
Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2008
Publication Date: 3/1/2009
Citation: Zhao, R., Wu, X., Seabourn, B.W., Bean, S., Guan, L., Shi, Y., Wilson, J.D., Madl, R., Wang, D. 2009. Comparison of Waxy vs. Nonwaxy Wheats in Fuel Ethanol Fermentation. Cereal Chemistry. 86(2):145-156. Interpretive Summary: Use of ethanol as a fuel additive has grown over the past few years, and this growth is expected to continue. Currently the majority of fuel ethanol in the US is produced from corn. However, as starch is the principal component of corn, other cereal grains including sorghum, wheat, millet, rice and barley are obvious ethanol feedstocks in areas where corn production is limited. While wheat markets in the US have traditionally been for milling, wheat is considered a potential energy crop in some parts of the world, such as Europe. Compared with corn, factors affecting ethanol yield for wheat are not well understood. In this study we found that non-waxy soft wheat had the highest ethanol yields (433 L/ton) than did non-waxy hard and waxy wheat. Waxy wheat had higher conversion efficiencies however. This research suggests that waxy wheat could be bred specifically for bio-fuel production.
Technical Abstract: Fermentation performance of 8 waxy, 7 non-waxy soft, and 15 non-waxy hard wheat cultivars was compared in a laboratory dry-grind procedure. With nitrogen supplemented into the mash, the range of ethanol yields was 368–447 L/ton. Non-waxy soft wheat had an average ethanol yield of 433 L/ton, higher than non-waxy hard and waxy wheat. Conversion efficiencies ranged from 91.3–96.2%. Despite having higher levels of free sugars in grain, waxy wheat had higher conversion efficiency than non-waxy wheat. Although there was huge variation in protein content between non-waxy hard and soft wheat, no difference in conversion efficiency was observed. Waxy cultivars had extremely low peak viscosity during liquefaction. Novel mashing properties of waxy cultivars were related to unique pasting properties of their starch granules. With nitrogen supplementation, waxy wheat had a faster fermentation rate than non-waxy wheat. Fermentation rates for waxy cultivars without nitrogen supplementation and non-waxy cultivars with nitrogen supplementation were comparable. Ethanol yield was highly related to both total starch and protein content, but total starch was a better predictor of ethanol yield. There were strong negative relationships between total starch content of grain and both yield and protein content of distillers dried grains with solubles (DDGS).