Flavor components of fats and oils

Chi-Tang Ho Rutgers University, New Bmnswick, New Jersey, Flavor Components of Fats and Oils. 

Flavor Components of Fats and Oils, Lipid Oxidation Measurement Methods, Marine Mammal Oils, Modification of Fats and Oils via Chemical and Enzymatic Methods, Novel Separation Techniques for Isolation and Purification of Fatty Acids and Oil By-Products, Quality Assurance of Fats and Oils, Tree Nut Oils. 

Analysis of Trace or Minor Components. Minor or trace components may have a significant impact on quaHty of fats and oils (94). Metals, for example, can cataly2e the oxidative degradation of unsaturated oils which results in off-flavors, odors, and polymeri2ation. A large number of techniques such as wet chemical analysis, atomic absorption, atomic emission, and polarography are available for analysis of metals. Heavy metals, iron, copper, nickel, and chromium are elements that have received the most attention. Phosphoms may also be detectable and is a measure of phosphoHpids and phosphoms-containing acids or salts. 

The processing technologies employed for production of fats and oils, and associated components, to make them shelf-stable with acceptable sensory characteristics and flavor as well as secondary processing technologies for production of specihc products are important considerations in this area. Food commodities... 

Flavors. Most of the flavors used in shortenings are butterlike. Diacetyl was the major butter flavor used in fat and oil products until improved analytical techniques identified other flavor components in butter. Today, the U.S. FDA regulations allow safe compounds that impart a suitable flavor to the finished product (16). The choice of a particular flavor or blend of flavors depends on the expertise and the taste preference of the product developer. 

Deodorization of fats and oils is a necessary process for removing disagreeable flavor and odor components that are naturally present or created... 

Many esters have fragrant odors and contribute to the flavors of fruits. For example, benzyl acetate, CH3COOCH2C6Hs, is an active component of oil of jasmine. Other naturally occurring esters include fats and oils. For example, the animal fat tristearin (12), which is a component of beef fat, is an ester formed from glycerol and stearic acid. 

Proteins are important food components mainly due to their nutritional and functional value. Dietary proteins provide amino acids and nitrogen necessary for organisms. They also play a major role in determining the sensory and textural characteristics of food products. The functional properties are related to their ability to form viscoelastic networks, bind water, entrap flavors, emulsify fat and oil, and form stable foams [105]. 

Palm Kernel Oil (Unhydrogenated) is a fat obtained from the kernel of the fruit of the oil palm Elaeis guineensis Jacq. (Fam. Arecaceae) by mechanical expression or solvent extraction. It is refined, bleached, and deodorized to substantially remove free fatty acids, phospholipids, color, odor and flavor components, and miscellaneous other non-oil materials. Like coconut oil, it has a more abrupt melting range than other fats and oils. 

Oxidative stability of edible oils depends primarily on their fatty acid composition and, to a lesser extent, in the stereospecific distribution of fatty acids in the triacyl-glycerol molecules. The presence of minor components in the oils also affects their oxidative stability. A detailed discussion of oxidative processes in fats and oils is provided elsewhere in this series. Oxidation may occur via different routes and includes autoxidation, photo-oxidation, thermal oxidation, and hydrolytic processes, all of which lead to production of undesirable flavor and products harmful to health. Flavor and odor defects may be detected by sensory analysis or by chemical and instrumental methods. However, chemical and instrumental procedures are often employed in the processing and during usage of edible oils. Indicators of oxidation are those that measure the primary or secondary products of oxidation as well as those from hydrolytic processes or from thermal oxidation, including polymers and polar components (15). 

The unsaturated fatty acids in all fats and oils are subject to oxidation, a chemical reaction which occurs with exposure to air. The eventual result is the development of an objectionable flavor and odor. The double bonds and the adjacent allylic functions are the sites of this chemical activity. Oil oxidation rate is roughly proportional to the degree of unsaturation for example, linolenic fatty acid (18 3) with three double bonds is more susceptible to oxidation than linoleic (18 2) with only two double bonds, which is ten or more times as susceptible as oleic (18 1) with only one double bond. Oxidative deterioration results in the formation of hydroperoxides, which decompose into carbonyls, and dimerized and polymerized gums. It is accelerated by a rise in temperature, oxygen pressure, prior oxidation, metal ions, lipoxygenases, hematin compounds, loss of natural antioxidant, absence of metal deactivators, time and ultraviolet or visible light. Extensive oxidation will eventually destroy the beneficial components contained in many fats and oils, such as the carotenoids (vitamin A), the essential fatty acids (linoleic and linolenic), and the tocopherols (vitamin E). 

Capillary supercritical fluid chromatography has been demonstrated as a viable alternative for the analysis of food components which are sensitive to temperature such as flavors and fragrances. Supercritical fluids have long been recognized for their unique solvating characteristics. One of the most common uses of supercritical fluids is for the extraction of components of interest from natural materials (i.e. caffeine from coffee or oil from soybeans). Early in its development supercritical fluid chromatography (SPC) was used for the analysis of natural materials such as flavors and other food components because the technique is well suited for the analysis of compounds which thermally degrade. In this paper, the use of capillary SFC for the analysis of food components is discussed. Examples of the capillary SFC analysis of fats and flavors as well as food contaminants such as pesticides are presented. 

Food. Common fennel is used as a flavor component in alcoholic beverages (especially liqueurs), baked goods, meat and meat products, fats and oils, snack foods, and gravies, with highest average maximum use level of about 0.119% (1186ppm) reported in meat and meat products. 

The stability of canola oil is limited mostly by the presence of linolenic acid, chlorophyll, and its decomposition products and other minor components with high chemical reactivity, such as trace amounts of fatty acids with more than three double bonds. These highly unsaturated fatty acids can possibly be formed during refining and bleaching (52). The presence of 7% to 11% of linolenic acid in the acylglyce-rols of canola oil places it in a similar category with soybean oil with respect to flavor and oxidative stability. The deterioration of flavor as the result of auto -and photo-oxidation of unsaturated fatty acids in oils and fats is referred to as oxidative rancidity. 

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