Iodine value of fats

Iodine monochloride [7790-99-0] ICl, mol wt 162.38, 78.16% I, is a black crystalline soHd or a reddish brown Hquid. SoHd ICl exists ia two crystalline modifications the a-form, as stable mby-red needles, d = 3.86 g/mL and mp 27.3°C and as metastable brownish red platelets, d = 3.66 g/mL, mp 13.9°C and bp 100°C (dec). Iodine monochloride is used as a halogenation catalyst and as an analytical reagent (Wij s solution) to determine iodine values of fats and oils (see Fats and fatty oils). ICl is prepared by direct reaction of iodine and Hquid chlorine. Aqueous solutions ate obtained by treating a suspension of iodine ia moderately strong hydrochloric acid with chlorine gas or iodic acid (118,119). 

American Oil Chemists Society. 1993b. AOCS Official Method Cd 125. Iodine Value of Fats and Oils—Wijs Method. Champaign, 111. 

Iodine Value of Fats and Oils—Cyclohexane Method (IV) (Cd lb-87) measures the unsaturation of fats and oils in terms of centigrams of iodine absorbed per gram of sample. The method is applicable to all normal fats that do not contain conjugated double bonds. It often is used to estimate the degree of hydrogenation of oils. 

TABLE 7. Titer and Iodine Values of Fat from Various Livestock Species Including Menhaden Fish Oil. 

Iodine monochloride. Mol. wt. 162.38, m.p. 14°, 27° b.p. 97°. Suppliers Alfa, E, F, KK, MCB. A solution of iodine monochloride in acetic acid (Wijs solution) is used to determine iodine values of fats and oils. 

Iodine monochloride is used to estimate the iodine values of fats and oils and as a topical anti-infective (Merck 1996). 

American Oil Chemists Society, Iodine value of fats and oils. Official Method Cd 1-25. 2211 West Bradley Ave., Champaign, IL 61826. 

Apart from specifications as to origin, e.g. palm kernel oil, fats are normally supplied on the basis of established parameters. One of these is the iodine value. This reflects the tendency of iodine to react with double bonds. Thus, the higher the iodine value the more saturated the fat is. An iodine value of 86 would approximate to one double bond per chain, while an iodine value of 172 approximates to two double bonds per chain. Another parameter is the peroxide value. This attempts to measure the susceptibility of the fat or oil to free radical oxidation. The test is applied on a freshly produced oil and measures the hydroperoxides present. These hydroperoxides are the first stage of the oxidation process. Obviously, this test would not give reliable results if applied on a stale sample. 

Analysis of Fats.—The iodine value of a fat or oil is a quantitative measure of the number of carbon-carbon double bonds which it contains. This number is the amount of iodine in grammes which combines chemically with 100 g. of the fat or oil. Nowadays the number of double bonds in organic compounds is usually determined with per-benzoic acid (cf. p. 111). 

Iodine monochloride is used as an analytical reagent to determine iodine values of ods and fats. It is dissolved in glacial acetic acid (Wijs solution) for the analysis. ICl is used in organic synthesis. It also is used as a topical antiseptic. 

Diacetyl Tartaric Acid Esters of Mono- and Diglycerides occur over a range in appearance from sticky, viscous liquids through a fatlike consistency to a waxy solid, depending on the iodine value of the oils or fats used in their manufacture. They are the reaction product of partial glycerides of edible oils, fats, or fat-forming fatty acids with diacetyl tartaric anhydride. The diacetyl tartaroyl esters are miscible in all proportions with oils and fats. They are soluble in most common fat solvents, in methanol, in acetone, and in ethyl acetate, but are insoluble in other alcohols, in acetic acid, and in water. They are dispersible in water and resistant to hydrolysis for moderate periods of time. The pH of a 3% dispersion in water is between 2 and 3. 

Melon, Cucumis melo, is a member of the Cucurbitaceae family and grows best in tropical regions. The pulp of the fruit has pleasant flavor and taste, and the seeds are generally treated as waste however, medicinal effects have been reported for the seeds (24, 25). Hexane-extracted seed oil of Cucumis melo hybrid AF-522 was determined to contain 64 g of linoleic acid per 100 g of total fatty acids (Table 4) (24). Significant amounts of oleic, palmitic, and stearic acids were also detected in the melon seed oil. The specific gravity (28°C), refractive index (28°C), and iodine value of the seed oil were 0.9000, 1.4820, and 112, respectively, under the experimental conditions (24). Earlier in 1986, Lazos (25) extracted the oil from Cucumis melo seeds and examined its physicochemical properties (25). Linoleic acid was the primary fatty acid and accounted for 64.6% of the total fat (w/w), along with 20.1% oleic acid, and 14.7% total saturated fatty acids (Table 4). Iodine value and refractive index (40°) of the seed oil were 124.5 and 1.4662, respectively. 

The roasted red pepper seed oil contained an extremely high concentration of linoleic acid, approximately 74%, and a high total unsaturated fat level (Table 6) (37). The fatty acid profile was very similar to that of both goldenberry seed (Physalis peruviana L.) and safflower oils (36). The iodine value of roasted red pepper seed oil was determined to be 137-g iodine/lOO-g oil.This shows that there is a high degree of unsaturation in the oil. Oxidative stabilities of the roasted red... 

Lard is prepared from the fat of the hog. It consists of stearin, palmitin, and olein, with a small amount of linolein. Fresh lard contains but a small amount of free acid (0,1 to 0.4 per cent). On exposure to the air partial decomposition takes place and the acidity increases. The iodine value of old lard is less than that of the fresh substance. 

The usual practice for the process operator is to determine the refractive index of a sample of the oil during hydrogenation, since this can be done in a few minutes, on site. It correlates well with the iodine value of the oil and also the solid fat index. If a hydrogen gas meter is available, this will have been set at a precalculated amount of gas at which to stop the reaction for determination of the refractive index. Calculation of the amount of gas required is based on the stoichiometry of hydrogenation (Mattil 1964). When the desired refractive index is reached, the batch is cooled for filtration and the solid fat index is determined in the laboratory. This is by far the most important analysis method in hydrogenation control. Typical solid fat indices for selectively and nonselectively hydrogenated canola oil are given in Table IV (Teasdale, 1975). 

To optimize this crystallization and finally obtain an oil/fat ratio optimal for the churning process, a defined temperature regime must be applied (see below). This regime depends strongly on the composition of the milk fat, which is subject to seasonal variations the iodine value of winter milk fat is about 30 and that of summer milk fat about 40. 

Cocoa butter substitutes are prepared by separating out a middle melting fraction from palm oil and blending the resulting product with other exotic tropical fats. These fats are called palm mid-fractions. The slip melting points and iodine values of a few such fats are also plotted in Fig. 8.2 for added interest. It is unlikely that palm oil will ever be adulterated or contaminated with a palm mid-fraction as these fractions command a high price and are traded separately from the conventional bulk oils. 

The dry mango stone consists of a 1 1 ratio of shell and kernel. Wide variations were found in the content, characteristics and composition of seed and fat of 43 varieties of mango fruit. The seed in fruit ranges between 3 and 25% and kernel in seed from 54 to 85% on an as is basis (Lakshminarayana et al., 1983). The total lipid consists of 96.1% neutral and 3.9% polar lipids (2.9% glycolipids and 1.0% phospholipids) (Hemavathy et al., 1987). The dry mango kernel from India contains 3.7-13% of a cream-colored oil with a melting point of 34-43 C and iodine value of 32-57. Its physical and chemical characteristics are very similar to that of cocoa butter. 

One attempt to classify fish fats (Lambertsen, 1978) is exemplified in Table 10.5. The percentages of as few as eight fatty acids of marine oils and lipids add up to about 80% of those present at 2-3% or more. Nutritionists may request 18 0, 18 2, 18 3 and 20 4, so 12 fatty acids have also been employed. Compared to lard, beef or sheep fats (see above), fish oils are considered highly unsaturated. One of the common trading standards of fish oils is the iodine value (IV). The iodine values of the monoethylenic fatty acids are 90 for 18 1 and 420 for 20 5n-3. Because of the extreme differences in IV for the typical two types of acids in Table 10.5, it was possible (Ackman, 1966) to develop an empirical formula percent polyunsaturated fatty acids = 10.7 + 0.337 (iodine value of oil—100). Table 10.6 shows the applicability of this formula. Since one of the objectives of the preparation of encapsulated fish oil products is to deliver 20 5n-3 and 22 6n-3 (Ackman et al., 1989 Sagredos, 1992), the iodine value is an easily utilized index of the suitability of raw materials for this or other uses. 

In this section, we consider the determinations based on the addition of bromine on double bonds. Most of the time, these addition reactions take place in nonaqueous media. We limit ourselves to recall the notions of iodine value and fat indices. Some drugs are determined by the addition of bromine on a double bond that their structures contain. We ll first consider cyclobarbital and hexobarbital, which are derived from barbituric acid ... 

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