Hydrogenation, fats temperature

Metal sulfides play an important role in catalyzing a wide variety of hydrogenations (e.g., of fats, coal, or olefins) and also desulfurization reactions, which are used in pretreatment of fossil fuels to reduce the emission of sulfur oxides during combustion (Section 8.5). Molybdenum disulfide, an important defect catalyst, can be made to function as an n-type (Moi+xS2) or p-type (Mo1 xS2) semiconductor by exposure to an appropriate mixture of H2S and hydrogen at temperatures on the order of 600 °C. The equilibrium... 

Recently new soaps have been found to improve greases with respect to melting point, adhesiveness, resistance to the washing action of water, and utility at both high and low temperatures. The newer thickeners are soaps of lithium 25) or barium 24) Certain properties of greases may be improved by saponification of the alkali with fats or fatty acids which have become available fairly recently these products include hydrogenated fats and pure fatty 13) acids such as 12-hydroxystearic acid. 

The storage temperature of hydrogenated fats must not exceed its melt point by 10°F (5.6°C)... 

Hydrogenation reactions are commonly used to convert the liquid unsaturated fats found in oils from plants such as soybean, corn, and peanuts into saturated fats that are solid at room temperature. These hydrogenated fats are then used to make margarine and solid shortening. You will learn more about the composition of fats in Chapter 24. 

Trans isomers always occur in oil-fried products because they are formed at high temperatures. The developments in fat hydrogenation with respect to process optinuzation and the selection of catalysts have resulted in a gradual reduction in FA trans isomers in partially hydrogenated fats. The result of complete hydrogenation, in which all bonds of unsaturated FA are saturated with hydrogen, are hardened fats that undergo further modification by interesterification. 

These derivatizations have not been used extensively since the catalysts are generally strong acids that would isomerize CLA. Furthermore, the separation characteristics of these esters, and the method of how the results of esters are integrated with the FAME results, have not been as well documented. Alternatively, some researchers have used a combination of GC columns the total FAME were analyzed on a shorter Carbowax type GC column (25 m), followed by resolution of the 18 1 to 18 3 isomers using a 100 m polar column operated at different isothermal conditions from 170 to 190°C (33,89,91,104,118). Isothermal temperatures between 170 and 190°C maybe appropriate for the analysis of partially hydrogenated fats (100) and specific regions of the milk FA profile, but not for the complete analysis of dairy fats that contain short-chain FA (15,34). In fact the new AOCS official method forTFA analysis (method Ce lh-05) recommends isothermal operation at 180°C, but this method is not suitable for ruminant fats (67). 

Melting Point, Open Tube—Softening Point ( Cc 3-25 ) determines the temperature at which a solidified fat, in an open capillary tube, softens sufficiently to slip and rise to the top of the heating bath. This method is applicable to fats such as coconut oil, stearin, hydrogenated fats, and hard tallows. The results sometimes are reported as melting slip point, but the method is different from the AOCS Slip Point (Cc 4-25). 

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