Background: Determination of Iodine value (IV) along with factors like acid value, peroxide value, saponification value, solid fat index, refraction value, and trans fatty acid content is an important factor in controlling edible oils and fats. In unsaturated fatty acids, IV is a measure of the degree of unsaturation. The range of figures for IV of the various groups of oils and fats are therefore different. The Iv is usually determined by wijs or Hanus titration method, but recently for quick determination FT-NIR has been introduced. In this study, we compare the IV figures of Hanus and FT-NIR methods.
Materials and methods: For this project, 20 samples (7 solid and 13 liquid) were obtained from domestic oil factories. 100-200mg of liquid oil (250mg of solid sample) were dissolved in 10ml of chloroform and 25ml of Hanus solution was added and kept in dark place for 30 minutes. 10ml of KI solution and 100ml of distilled water were then added and titrated with sodium thio sulfate (0.1N). After the color of solution turned yellow, 2-3 drops of starch solution was added and titration was continued until the blue color disappeared. IV was then calculated using Hanus equation. For FT-NIR all liquid samples were put into sample holding directly and solid samples first melted and then poured into sample holding and IV was determined using special software.
Results: IV figures showed 0.5 to 4.5% (65% < 3% and only 35% showed 3 to 4.5%) difference between the two methods (NS). 90% of samples showed higher IV with FT-NIR as compared to Hanus method. Determining IV by Hanus required 45-60 minutes, whereas for FT-NIR it will take 2-3 minutes.
Conclusion: Results have revealed the feasibility of using FT-NIR to measure IV in oils and fats. There are major advantages of using FT-NIR as follows: provide faster analysis method, no sample preparation is required, eliminating the usage of solvents, reagents and glassware in control laboratories and finally very low level of operator error may occur.