Iodine value IV

Measurement of Unsaturation. The presence of double bonds in a fatty acid side chain can be detected chemically or through use of instmmentation. Iodine value (IV) (74) is a measure of extent of the reaction of iodine with double bonds the higher the IV, the more unsaturated the oil. IV may also be calculated from fatty acid composition. The cis—trans configuration of double bonds may be deterrnined by infrared (59) or nmr spectroscopy. Naturally occurring oils have methylene-intermpted double bonds that do not absorb in the uv however, conjugated dienes maybe deterrnined in an appropriate solvent at 233 nm. 

An important chemical characteristic of unsaturated acids is the iodine value (IV), which indicates the average degree of unsaturation. It is equal to the number of grams of iodine absorbed under standard conditions by 100 g of the unsaturated acid. 

The determination of iodine value (IV), AOCS Tg 1-64, is sometimes used to determine the extent of unsaturation. Because the tertiary aUyflc hydrogen ia the compounds is capable of substitution by halogen atoms, this only approximates a value for the degree of unsaturation. 

The composition of an oil and the progress of its hydrogenation is expressed in terms of its iodine value (IV). Edible oils are mixtures of unsaturated compounds with molecular weights in the vicinity of 300. The IV is a measure of this unsaturation. It is found by a standardized procedure. A solution of ICl in a mixture of acetic acid and carbon tetrachloride is mixed in with the oil and allowed to reac t to completion, usually for less than I h. Halogen addition takes place at the double bond, after which the amount of unreacted iodine is determined by analysis. The reaction is... 

A further example of process quality monitoring and reactor batch profiling using NIRS comes with oleo-chemical and biodiesel production. An established use of FT-NIR analysis (AOCS Method Cd le 01) is the determination of the key vegetable oil processing parameters - iodine value (IV) and percentage trans fat content (%Trans) (Figure 5.38). 

Figure 5.38 NIR spectra of vegetable oils and iodine value (IV) calibration.

The degree of unsaturation of the fatty acids is normally expressed as the iodine value (IV), that is, the number of grams of iodine that have reacted with 100 g of product analyzed, under controlled experimental conditions. The higher is IV, the greater is the degree of unsaturation. For example, for biodiesel intended for haulage use, the most remunerative use, a maximum IV limit of 120 g I2 per 100 g is envisaged. 

This unit defines three different tests that are used to evaluate lipid systems. The first two, i.e., iodine value (IV see Basic Protocol I) and saponification value (SV see Basic Protocol 2), are used to determine the level of unsaturation and the relative size (chain length) of the fatty acids in the system, respectively. The free fatty acid (FFA) analysis (see Basic Protocol 3) is self-explanatory. Each of these analyses provides a specific set of information about the lipid system. The IV and SV provide relative information this means that the data obtained are compared to the same data from other, defined lipid systems. In mixed triacylglyceride systems there is no absolute IV that indicates the exact number of double bonds or SV that indicates the exact chain length. The data from the FFA analysis is an absolute value however, the meaning of the value is not absolute. As a quality indicator, ranges of FFA content are used and the amount that can be tolerated is product and/or process dependent. 

The iodine value (IV) is used to determine the level of unsaturation in a fat/oil system. It is expressed as the number of grams of iodine that add to/react with 100 g of sample. The traditional iodine value method using the Wijs reagent requires carbon tetrachloride (CC14). For safety reasons, CC14 is no longer considered to be an acceptable chemical and it is not readily available for purchase, and if offered it is extremely expensive. Therefore the traditional method has been modified to a more human-friendly system which uses cyclohexane. 

Table D1.4.5 Iodine Value (IV), Fatty Acid Composition, and Solid Fat Index (SFI) of Canola Oil" ...

Gonzalez Gomez et al. (2002) applied crystallization fractionation to UCOME (Table 1.5). Following crystallization at a cooling rate = 0.1 °C/min, fractionation reduced CFPP from -1 to -5°C and total saturated FAME content from 19.2 to 14wt%. Again, liquid yields were low (25-30wt%). Krishnamurthy and Kellens (1996) reported that application of crystallization fractionation to TME increases iodine value (IV) from 41 to 60 and reduces CP from 11 to -1 °C with liquid yields of 60-65%. 

The unsaturation, as determined by the iodine value (IV), decreases from an IV of 10.0 for a single press to an IV of 1.0 for a triple press stearic acid grade. 

In the hardening of free tallow fatty acids in sc CO2 we measured iodine values (IV) below 1 g I2/IOO g product at a space velocity of 15 h1. In comparison to trickle bed hardening reactions with activated carbon and titania supported 2 wt. % palladium fixed bed catalysts, between 6 to 15 times higher space time yields were determined when the hardening was carried out in sc CO2. The hydrogen partial pressures in both processes were comparable (2.0 MPa H2). 

The product quality was analysed using silver-ion-HPLC and gradient elution [14]. This method was developed from an isocratic method [15]. The kind (cis/ trans) and the amount of the FAME was determined. From these data the iodine value (IV) was calculated. 

Iodine value (IV) g iodine/100-g sample (WIJS method)... 

The iodine value (IV) is an empirical test indicating the degree of unsaturation of a fat or oil. It is defined as the number of grams of iodine absorbed by 100 g of fat. 

Under normal fractionation conditions, soft stearins and oleins with cloud points in the range of 8-10°C are produced. Where required, fractionation conditions could be specifically altered to produce stearin or olein of a desired specification for specialized application, but within the domain of the composition of pahn oil. For example, stearins of differing iodine values (IV) ranging from the hard (IV of about 20) to soft (IV of about 50) could be produced, each with their characteristic solid fat content curve as shown in Figure 4. 

Iodine Value IV varies with the species of fish. In general, IV is a measure of the unsaturation in oils. High IV oils are generally more susceptable to oxidation. 

Base stock consistency control is the secret to first pass yield, i.e., meeting finished product specification limits with the specified blend of base stocks. Most finished shortenings physical characteristics are controlled with solids fat index (SFI) iodine value (IV), and/or a melting point analysis. However, time restraints during hydrogenation do not allow the long elapsed times required for these results. More rapid techniques to control base stock end points are ... 

By arranging all the vessels for gravity drop, very rapid turnover of batches in the reactor results. In this manner, the reactor is used for reaction only all heating, cooling, and hltration is accomplished external to the reactor. For example, if the average iodine value (IV) drop for all basestocks produced can be achieved in one hour, then a single system can deliver 24 batches per day (a 24-hour period). 

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