Academic literature on the topic 'Purification silicium'

"are purified lipid contents and others are not, and the puri-(Paspalum scrobiculatum), and barnyard (Echinocloa fied lipid content depends on the purification method. colona). Sridhar and Lakshminarayana [32] also reported Starch lipids (SL) are those bound to starch, and they FL contents of 5.0, 5.6, and 2.2% for Proso, Foxtail, and are the most difficult to extract. Since true SL are present Finger millet, respectively. Taira [45] found slightly high-inside the starch granules, even a very polar solvent such er average FL (ether extraction) contents for glutinous as WSB cannot extract them at ambient temperature. Effi-foxtail millet (4.2-5.1%, average 4.7% of 21 samples) cient extraction of SL requires mixtures of hot aqueous al-than for nonglutinous foxtail millet (4.0-4.7%, average cohol in proportions optimized for controlled swelling of 4.4% of 31 samples). Among millet, pearl millet contains the starch granules and solubilization of the lipids [25]. the most FL. The best solvents are n-propanol or isopropanol with water Lipid contents of rice in Table 2 were cited by Morrison (3:1, by volume) used under nitrogen at 100°C. However, [3] using the data of Nechaev and Sandler [2]. Taira and some n-butanol—water and methanol-water mixtures also Chang [46] reported that the average nonglutinous brown are reasonably efficient extraction solvents at 100°C [25]. rice FL (ether extraction) contents of 20 varieties each of Recently, a third lipid category was introduced. Starch sur-Indica and Japonica types were 2.7% (2.38-2.91%) and face lipids (SSL) are portions of the nonstarch lipids 2.9% (2.54-3.58%), respectively. More recently, Taira et (NSL), which become firmly absorbed onto or into starch al. [47] reported the average FL contents of 15 nongluti-granules during the separation of pure starch [24]. nous varieties as 2.5% (2.24-2.97%) for Indica, 2.5% Lipids are minor components of the cereal grains shown (2.12-2.94%) for Japonica, 2.7% (2.35-3.03%) for Sinica, in Table 2. Data in this table, expressed on a dry basis, and 2.6% (2.11-2.99%) for Japonica types. were calculated from reported values [3,16,26-41]. Also, some BL or TL contents were calculated by subtracting FL from TL or by adding FL to BL, depending on the avail-B. Nonstarch Lipid Classes of Grains ability of data. The FL contents range from 1.5 to 2% of Lipids can be separated into three broad classes by open-the kernel weights of barley, rice, rye, triticale, and wheat column silicic acid chromatography. Nonpolar lipids (NL) grains. They range from 3 to 7% of the kernel weights of are first eluted by chloroform, glycolipids (GL) are eluted oats, millet, corn, and sorghum. However, BL contents in next by acetone, and phospholipids (PL) are eluted last grains are more uniform than FL contents. Therefore, the with methanol. Mixtures of GL and PL are polar lipids FL:BL ratio is substantially higher for corn, millet, oats, (PoL). After NL elution from a silicic acid column, PoL and sorghum than for rye, triticale, and wheat grains. The can be eluted with methanol without the GL elution step. FL:BL ratios for barley and rice are intermediate. Lipids can also be separated into various classes by thin-High oil-containing grains such as corn are continuous-layer chromatography (TLC) using different development ly bred for higher oil content with improved production solvent systems. Each individual lipid class migrates dif-yield. Application of wide-line NMR spectroscopy for ferently on the thin-layer plate, and the difference in mi-nondestructive analysis of the oil content in single corn gration rates makes it possible to separate complex lipids kernels made selection for higher oil content more efficient into classes. The NL consists of SE, TG, DG, MG, and [42]. Corn hybrids with 6-8.5% oil content and grain FFA (see Table 1). The total NL content is obtained by yields equal to those of good commercial hybrids were adding these NL class contents as measured by densitome-produced [43]. try. Thus, the NL content of samples may differ, to some Several kinds of millet exist, and the lipid data in the extent, depending on methodology used (column separa-literature are confusing. Rooney compared the FL (ether tion or TLC separation). extraction) contents of several types of millet in a review The data [1,13,27,29,32,36-38,40,48-58] shown in paper [16]. The average FL contents of pearl millet (Pen-Table 3 may be used for only approximate comparison of nisetum typhoids) were 5.1% (4.1-5.6%, 14 samples), the NL content from different grains because some were 5.4% (2.8-8.0%, 167 samples, [44]), 5.6% (4.3-7.1%, 40 obtained by column chromatography and some by TLC. samples), and 6.2% (4.2-7.4%, 35 samples) [16]. Other All cereal grain lipids are richer in NL than in other class-reported average FL contents were 4.8% (4.6-5.0%, 6 es: 60-70% of the TL are NL in wheat (hexaploid), triti-samples) for foxtail millet (Setaria Italica), 5.8% cale, and rye; 65-80% for barley and oat groats; 77-87% (5.5-6.3%, 6 samples) for Japanese millet (Echinochloa for sorghum and rice; and 75-96% for corn and millet crusgalli), and 4.2% (3.8-4.9%, 20 samples) for proso (Pennisetum americanum). Sridhar and Lakshminarayana millet (Panicum miliaceum) [16]. Sridhar and Lakshmi-[32] reported 82, 80, and 79% of NL for Foxtail, Proso, narayana [30] reported a FL content range of 3.4-5.7% for and Finger millet, respectively. There are significant vari-small millet, including little (Panicum sumatrense), kodo etal effects on the NL/PoL ratio for corn and millet (P." In Handbook of Cereal Science and Technology, Revised and Expanded. CRC Press, 2000. http://dx.doi.org/10.1201/9781420027228-43.