Fruit iodine concentration

The mean iodine concentration in other foodstuffs, e.g., meat and meat products, bread and cereals, vegetables, potatoes, fruits and berries, and fats and oils, is 2—3pg/100g and their contribution of iodine to total iodine intake are assumed to be limited (Dahl et al., 2004). As a consequence of the high iodine concenttation in eggs, eggs are of equal importance to total iodine intake as the sum of bread, cereals, vegetables and fruits. 

O Design a titration that uses an iodine solution to determine and compare the concentration of vitamin C in a variety of fresh fruit juices. You may find it helpful to research appropriate procedures on the Internet. Include a method for standardizing the iodine solution. (See Challenge question 1.) Make sure that you list all the safety precautions you will use in your titration. Check your procedure with your teacher, and then carry out your titration. 

A method of determining airborne iodine has also been reported.241 Here, iodine is absorbed into 5% aqueous KI and spectrophotometrically determined at 590 nm in the form of its complex with starch. This method is selective with respect to bromine and chlorine, and the sensitivity of this method is 0.25 mg of I2 per m3 of air. The concentration of the, 31I isotope in water can be determined by a method involving isotope exchange in the starch-iodine complex.242 Flow-injection determination of ascorbic acid (0.1-40 mg/mL) has been proposed.243 Iodine is generated in the flow system as I3- ions, which are in turn exposed to starch to produce a steady signal at 350 and 580 nm. Ascorbic acid provides inversed maxima which are measured. This method is recommended for analysis of ascorbic acid in fruit juice, jam, and vitamin-C preparations. Use of the blue complex has also been reported for determination of sodium dichloro-isocyanurate in air.244 Obviously the blue reaction is applicable in the determination of amylose, amylopectin, and starch,245-252 as well as modified starches.245,253-255... 

C. Food harvested from an area that is contaminated by radiation may present a hazard. Meats and milk are the most vulnerable products because of the possibility for concentrations of radioactive isotopes (strontium, cesium, and iodine). All unpackaged and uncovered food, such as vegetables, fruits, and carcass meats, should be considered contaminated if obtained from a known area of contamination. If food supplies are critically low, the contaminated supplies may have to be consumed. In this event, it may be advisable to dilute the contaminated food by mixing with uncontaminated food. For more information, see page 1-34 of Effects of Nuclear Weapons and Directed Energy on Military Operations published by the AMEDD Center and School. 

It is interesting that a comparison of concentrations analyzed 80 years later for the 2003—2004 New Zealand Total Diet Survey (NZTDS) (Vannoort and Thomson, 2005) indicates that the iodine content of cereals, fruits, vegetables and meat is similar to the previous values (Table 129.1). 

Note that the smaller the number of drops, the higher the vitamin C content. This is because the amount of iodine is fixed beforehand. Students may need help to realise that the highest concentrations of vitamin C are found in the juices needing the smallest number of drops to react with all the iodine. The starch solution is needed to produce a consistent, visible end point. In Table 10.5, kiwi fruit are shown to have the highest concentration of vitamin C. 

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