|Flores, Rolando - UNIV. OF NEBRASKA-LINCOLN|
Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 27, 2007
Publication Date: October 30, 2007
Citation: Moreau, R.A., Wayns, K., Flores, R.A., Hicks, K.B. 2007. Tocopherols and tocotrienols in barley oil prepared from germ and other fractions from scarification and sieving of hulless barley. Cereal Chemistry. 84(6):587-592. Interpretive Summary: Barley kernels have been reported to contain several types of nutraceutical compounds that have health-promoting properties. These include two types of "functional lipids," phytosterols and Vitamin E analogs. The vitamin E analogs include tocopherols and tocotrienols, which are potent antioxidants and are thought to be important for cardiovascular health. Most barley that is included in food products is "pearled" or scarified to abrade the fibrous hull, which improves the flavor and also creates pearled kernels that are enriched in starch, protein, and other nutrients. In the current study we measured the levels of functional lipids in barley kernels and in the "pearling fines," (the abraded outer layers of the kernels). We then separated the pearling fines into four fractions with increasing particle sizes. We found that levels of phytosterols were similar in all four fractions. However, the levels of tocopherols were highest in the larger particle size fractions and the levels of tocotrienols were highest in the smaller particle size fractions. Our previous studies indicated barley fines oil appears to have the highest levels of tocotrienols of any known natural oil. The current study indicates that it is possible to control the ratio of tocopherols to tocotrienols in barley oil by separating the pearling fines into a specific particle size range before oil extraction. Tocotrienols are receiving much attention for their cholesterol-lowering and anticancer properties. The current study provides useful new information which will now make it possible to design a process to produce a barley fines oil with optimal concentration of tocotrienols or optimal tocopherols/tocotrienol ratio.
Technical Abstract: Two cultivars of hulless barley (Doyce and Merlin), were scarified to abrade the outer layers of the kernels (germ, pericarp, and aleurone). The resulting scarification fines fractions were then separated into four particle size subfractions using sieves. Each of the size subfractions was then extracted with hexane to produce a barley oil and the levels of free phytosterols, tocopherols and tocotrienols in the various barley oils were compared. For both cultivars, the fraction with the largest particle size (0.717 – 1.410 mm) had the highest oil yields (11-12 %). Visual examination of this fraction indicated that it was comprised almost entirely of small fragments (~1mm) of the germ portion of the kernel. The levels of tocopherols were highest in the largest particle size fraction and their proportion decreased in the fractions with decreasing particle size. In contrast, the levels of tocotrienols were very low in the largest particle size fraction and increased in the fractions with decreasing particle sizes. Intact germ was also prepared by hand dissection, extracted and analyzed. The results indicate that the ~1mm fragments obtained by scarification-sieving were comprised almost entirely of germ fragments, but these fragments only represented 17.5 and 23.7% of the total mass of the germ, from Merlin and Doyce, respectively. These results also suggest that it may be possible to control the concentrations of tocopherols and tocotrienols in barley oil by controlling the particle size of the feedstock used to extract the oil. Germ fragments isolated by such processes could potentially be used as functional food ingredients or extracted to yield oils enriched in health-promoting phytosterols, tocopherols and/or tocotrienols.