C: Food Chemistry Comparison of Lipid Content and Fatty Acid Composition and Their Distribution within Seeds of 5 Small Grain Species KeShun Liu Abstract: Barley, oats, rice, sorghum, and wheat, each with two genotypes, were sequentially abraded by an electric seed scarifier. The pearling fines (PF) and pearled kernels (PK) at each cycle were analyzed for lipid (mostly nonpolar) content and fatty acid (FA) composition. The oil content in whole or dehulled grains ranged from 2.18% of a wheat variety to 6.38% of an oat line. Compared with barley and wheat, rice, oat, and sorghum had higher relative % of C18:1 (31.60 to 36.64 compared with 12.15 to 15.61) and lower % of C18:2 (35.69 to 45.44 compared with 50.79 to 61.50). The relationship between oil content in PF and the cumulative level of surface removal essentially describes the distribution pattern of oil content within a seed. Barley, rice, and sorghum had a similar distribution pattern, characterized by a rapid rate of decreasing for the first few outer layers and then by gradual decrease to a flat value toward the inner core. In contrast, distribution within oats was characterized by a gradual reduction in oil content across the seed. The distribution of oil within wheat fell between the former 2 types. For all 10 grains, from seed surface to inner core, C16:0 and C18:0 increased, C18:1 and C18:3 decreased, and C18:2 changed slightly, providing a new reason for improved oxidative stability for pearled kernels. The differences in the changing intensity of FA composition among grain species correspond to those in oil distribution within a seed, while varietal difference in distribution patterns of content and FA composition of lipids within a species was insignificant. Keywords: distribution, fatty acid, grains, oil content, pearling Practical Application: This study was the first to document fatty acid distribution across a grain seed. Results provide 2 major reasons for improved oxidative stability of pearled grains: reduced oil content and shift of fatty acids toward more saturated and less unsaturated composition. Introduction For the majority of the world population, cereal-based foods constitute the most important source of energy and nutrients. Cereal grains are generally divided into several structural parts, including hulls, pericarp, testa, embryo (germ), aleurone, and en- dosperm. These structural parts vary in composition, nutritive values, and end uses. This feature dictates heterogeneous distribu- tion of nutrients throughout a seed. Several processing methods, such as roll milling, de-germinating, and pearling, have been used to remove germ and/or outer layers of cereal grains. The processes reduce undesirable components, such as phytate (Liu and others 2007), while improve certain characteristics of remaining kernels, such as appearance, texture, cooking quality, oxidative stability, and digestibility (Klamczynski and others 1998, Yeung and Vas- anthan 2001). Equally important is that germ and bran fractions removed from grains generally have increased end-use values due to concentration of many beneficial nutrients, such as lipids, pro- MS 20101120 Submitted 9/30/2010, Accepted 11/23/2010. Author is with Grain Chemistry and Utilization Laboratory, Natl. Small Grains and Potato Germplasm Research Unit, USDA-ARS, 1691 S. 2700 West, Aberdeen, ID 83210, U.S.A. Direct inquiries to author Liu (E-mail: Keshun.Liu@ars.usda.gov. tein, vitamins, minerals, and nutraceuticals (Summer and others 1985; Lampi and others 2004; Liu and Moreau 2008). This has led to commercial production of corn germ oil, rice bran oil, and wheat germ oil. Compared to starch and protein, the content of lipids in most cereals is relatively low (about 3%). Their contribution toward the nutritional value as well as storage stability of cereal-based food or feed, however, is important. Therefore, various studies have been carried out to document the content and fatty acid (FA) compo- sition of lipids in whole grains (Welch 1975; Price and Parsons 1975; Zhou and others 1998; Osman and others 2000; Mehmood and others 2008) as well as in several structural parts (Youngs and others 1977; Price and Parsons, 1979; Hargin and Morrison 1980; Bradbury and Collins 1982; Banas and others 2007) from grains of different species and varieties. However, research on distribu- tion of lipid content across a cereal seed has been limited (Liu and Moreau 2008), while none has reported on distribution of FA composition within a cereal grain. In this study, 5 small grain species, each with 2 genotypes (va- rieties or breeding lines), were sequentially pearled. The pearling fines (PF) as well as corresponding pearled kernels (PK) at each cycle were analyzed for lipid content and FA composition. The objective was to compare lipid content, FA composition, and their distribution patterns within a seed among grain species. Journal compilation C  2011 Institute of Food Technologists R  No claim to original US government works C334 Journal of Food Science  Vol. 76, Nr. 2, 2011 doi: 10.1111/j.1750-3841.2010.02038.x Further reproduction without permission is prohibited