Com germ oil

The major component of cmde com germ oil is triacylglycerols, but the cmde oil also contains other minor nonpolar and polar lipid components (Table 3). Free... 

Squalene is an unsaponifiable compound in corn oil that has not received much attention. Squalene was previously reported to be the major hydrocarbon in com oil (43) and we recently reported that both com germ oil and corn fiber oil contain about 0.2% squalene (40). 

Although FFA content of the oil varies considerably depending on the preharvest and postharvest conditions, it is usually in the range of 1-1.5% of the total acyl lipids. Wet milled corn germ oil contains higher FFA content than that of the dry milled oil, 1.5 % and about 2%, respectively (7, 66). The PL content of com germ oil varies with the extraction process. Expelled oil contains about 120 ppm PL as compared with 670 ppm in hexane prepress commercial products (66). 

Sterols The total phytosterol content (free and esterified phytosterols) of corn germ oil is higher than in most of the other vegetable oUs (3, 70). Com germ oil contains about 1.1% (w/w) phytosterol esters (70). Sitosterol is the major sterol... 

Karlovic et al. (79) examined the aqueous enzymatic extraction of com germ oil. Hydrothermal pretreatment, grinding, and enzymatic treatment of corn germ improved extraction efficiency. Although the energy cost for enzymatic com germ oil extraction was lower than that of the conventional extraction, the enzyme cost made the process more expensive (79). 

Com germ oil contains two phytosterol lipid classes, free phytosterols and phytosterol fatty acyl esters (Table 10.1). Phytosterols have been recognized as one of the twelve most important classes of phytonutrients (Fahey et al. 1999). Most chemical identification of phytosterols in vegetable oils has been conducted by saponifying (hydrolyzing with base) the oil and measuring the resulting free phytosterols, usually by GLC (Table 10.4). The major phytosterols... 

Worthington and Hitchcock (1984) reported, on the basis of GC examination, that squalene was the major hydrocarbon in com germ oil and Moreau and coworkers (2000) recorded about 0.2% of squalene in both the fiber and the germ oils. 

The concentration of heavy metal ions that results in fat (oil) shelf-life instability is dependent on the nature of the metal ion and the fatty acid composition of the fat (oil). Edible oils of the linoleic acid type, such as sunflower and com germ oil, should contain less than 0.03 ppm Fe and 0.01 ppm Cu to maintain their stability. The concentration limit is 0.2 ppm for Cu and 2 ppm for Fe in fat with a high content of oleic and/or stearic acids, e. g. butter. Heavy metal ions trigger the autoxidation of unsaturated acyl lipids only when they contain hydroperoxides. That is, the presence of a hydroperoxide group is a prerequisite for metal ion activity, which leads to decomposition of the hydroperoxide group into a free radical ... 

Dittmar, D., de Arevalo, A. M., Beckmann, C., Eggers, R. (2005). Interfacial tensitm and density measurement of the system com germ oil—Carlxm dioxide at low temperatures. European Journal of Lipid Science and Technology, 107, 20-29. 

Maize oil (com oil) is obtained from maize germ (the embryos of Zea mays L.) (Codex Alimentarius, 1999). Unlike most other vegetable oils, com oil (maize oil) is obtained from seeds (kernels) that only contain 3-5% oil. Obtaining oil directly from the kernels is technically possible, but com kernel oil would be costly to produce, because of the low levels of oil in the kernels. Com germ is rich in oil (>30%), and is the source of all the commercial com oil, which could more accurately be called com germ oil (Gunstone, 2011). 

The examination of the total phytosterols in com oil has revealed that the major phytosterol was P-sitosterol (Table 6). The major phytosterols in com germ oil are P-sitosterol > eampesterol > stigmasterol (Table 6). P-sitosterol is also foimd in the form of femlate ester, displaying antioxidant properties. 

In this chapter an environmental friendly extraction process of com germ oil based on the use of supercritical CO2 (SC-CO2) is presented. The effect of important operating parameters in supercritical fluid extraction (SEE) processes such as pressure, temperature and flow rate on the extraction kinetics and the quality of the extracted oil is discussed. As for many SC-CO2 extractions of vegetable oils, extraction curves of com germ oil present an initially linear part with a slope close to the oil solubility value in CO2. Then, a second section of the extraction curve is determined by the diffusional resistance in the solid matrix. Characterization of supercritical cmde com oil is presented by showing some properties reported in the literature such as physical parameters, fatty acid composition, neutral lipids, content of tocopherols, acid index, peroxide value, antioxidant capacity and the oxidative stability. 

Com germ oil is mainly used in food and cosmetic applications and com germ meal for animal feed production. 

Figure 1. Flow diagram of the wet milling process for obtaining com germ oil.

In the last decades, some more environment friendly procedures have been suggested for com germ oil production, among them, the use of enzymes to enhance the oil recovery and/or extraction of oil by using supercritical fluid extraction (SFE) (Matthaus, 2012). This chapter is focused on the SFE process of com germ oil, paying special attention to the description of the process and the influence of process parameters on the quality of the resulting oil. 

SFE of com germ oil, although not yet at an industrial scale, has been studied by several authors, including some recent patents related to SFE of com germ oil and SF fractionation of the extracted oil to obtain a refined com oil (DeLine et al., 2009, DeLine et al., 2013, Marentis, 2013). 

One of the first studies about SFE of com germ oil was performed by the Agricultural Research Service of the United States Department of Agriculture (Peoria, Illinois). List et al., (List et al., 1984, List and Friedrich, 1989) and Christianson et al., (Christianson et al., 1984) compared the quality of cmde oils obtained from dry and wet milled com germ using SFE at 50-90°C and 55-83 MPa and conventional extraction methods. They concluded that the oil obtained by SC-CO2 extraction exhibited lower refining loss and lighter color. 

Different parameters can be employed to eharacterize the extracted com germ oil such as physical parameters (e.g. refraetive index, density, color) and chemical parameters, including composition in terms of fatty acids profile by gas ehromatography (AOAC, 1995) and neutral lipids, that can be determined, among other analytical methods, by liquid chromatography (Schaefer et al., 2003). 

Table 2. Process parameters used in the experiments of SFE of com germ oil with...

Figure 5. Influence of extraction temperature on com germ oil extraction yield ( 40°C A 63°C O 79 C 85°C), at around 45.0 MPa and 9 kg C02/h.. Solid lines correspond to the model of Sovova...

Effect of solvent flow rate. The effect of solvent flow rate has been studied by Rebolleda et al., (Rebolleda et al., 2012) and their results are presented in Figure 7 at a constant pressure and temperature. Extraction curves, expressed in dependence on the solvent-to-feed ratio, are not significantly affected by SC-CO2 flow rate. This behavior supports the fact that solubility, not external mass transfer, is controlling the SC-CO2 extraction process of com germ oil. 

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