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Amino-acid score of foods

a. The values listed are grams per 100 grams for nitrogen and protein and milligrams per 100 grams for each of the amino acids. They are summarized from FAO Nutritional Studies No. 24 (FAO, Rome, 1970). Values for nitrogen and protein are given as grams per 100 grams of food, and the amino-acid values are given as milligrams per 100 grams of food. When the amino-acid content is recorded as "-0," it means no data were available.
b. The values for this section are from Food for Peace [4] .

REFERENCES

1. P. L. Pellett and V. R. Young, Nutritional Evaluation of Protein Foods, UNU Food and Nutrition Bulletin Supplement No. 4 (United Nations University, Tokyo, 1980).

2. Joint FAO/WHO/UNU Expert Consultation on Protein-Energy Requirements (WHO, Geneva, 1985).

3. W. M. Rand, R. Uauy, and N. S. Scrimshaw, Protein-Energy-Requirement Studies in Developing Countries: Results of International Research, Food and Nutrition Bulletin Supplement No. 10 (United Nations University, Tokyo, 1984 ).

4. Food for Peace, PL480, Title 2, Commodities Reference Guide (Agency for International Development, Washington, D.C., 1977).

NEW UNU PUBLICATIONS

Energy Systems Analysis in Food and Energy Crop Production. By Malcolm Slesser. UNU/FEN, 1985. Citizen Organizations and Food Energy Alternatives in Indian Cities. By Narendra Panjwani. UNU/FEN, 1985. Use of Dynamic Systems Analysis to Assess the Potential for Enhanced Output in the Rural Communities of Developing Countries. By Chris Lewis. UNU/FEN, 1985.

These three small pamphlets are the first essays to come from the Food Energy Nexus Programme of the United Nations University. In the first Malcolm Slesser demonstrates that energy analysis provides a sensitive tool for appraising the resource implications of both food and energy crops. Expression of inputs in terms of their gross energy requirements provides the most sensitive measure of energy use. Such data can be useful in planning.

In the second pamphlet Narendra Panjwani draws attention to significant experiments by voluntary organizations to introduce energy alternatives in Indian cities. He concludes that ingenious small projects can contribute to improvement of the city and cut down on the wasteful use of energy in the absence of comprehensive solutions. However, the communications gap between scientists working on renewable energy technologies and developmental activists working among the urban poor has still to be bridged and low-energy strategies have yet to be made an integral part of strategies for urban development.

The third of the essays, by Chris Lewis, attempts to demonstrate the application of dynamic systems analysis to the selection of technologies and improved agricultural practices. Its application to a small community in southern India shows a potential for changing the village from a net energy importer to an exporter, with marked increases in food production and indigenous energy utilization.

A simple field kit for testing iodine in salt

B. S. Narasinga Rao and S. Ranganathan
National Institute of Nutrition, Indian Council of Medical Research, Jamai-Osmania, Hyderabad-500007, India

A programme of distribution of iodized salt in the areas where goitre is endemic has been in operation in India for the past two decades. Owing to operational bottlenecks, such as underproduction and poor distribution, iodized salt is not at present reaching all these areas regularly. Recently the Government of India decided (i) to increase progressively the production of iodized salt with the aim of meeting the needs of the endemic areas, and (ii) ultimately to iodize all edible salt in India. Effective implementation of a programme for iodized salt distribution to control and eradicate goitre requires regular monitoring of edible salt for iodine, particularly at the retail sales level and the household level.

Dustin and Ecoffey [1] have reported a field test for the detection of iodine in salt in which a starch solution, an acid solution (hydrochioric-sulphuric), and a sodium nitrite-potassium iodide solution are used. These solutions are carried in a portable kit in stoppered glass bottles. Under tropical conditions the starch solution is the least stable. Hydrochloric acid and sulphuric acid are quite corrosive and hence cumbersome to carry, and a sodium nitrite-potassium iodide solution is also unstable.

The purpose of this article is to describe a kit that can be made up and used by field workers who have no knowledge of chemistry.

The new kit is very simple: tablets instead of solutions are used and only distilled water need be carried if it is not available locally. All the materials can be carried in a small portable kit, and the required solutions can be prepared on the spot. The proposed method is highly sensitive, less expensive than other tests, and more appropriate for use by public health workers in the goitre-endemic areas.

TESTING IODIZED SALT IN INDIA

Satisfactory processes are available for the manufacture and distribution of iodized salt with fairly stable iodine content. While industrialized countries stipulate potassium (or sodium) iodide, developing countries prefer potassium iodate, as it shows better stability during transportation and storage, particularly in tropical climates where salt has a high moisture content. We have developed kits for testing both iodide and iodate in salt. Either method can be used depending upon the source of iodine in the salt; if the source is not known both tests can be applied.

For routine analysis it is convenient to compare the unknown salt with a standard sample of salt iodized according to the local regulations and to use only the test appropriate for the standard. Since in India iodate is normally used in iodized salt, the iodate test can be carried out routinely.

IODATE TEST

The test described will detect the presence of iodate over the range of recommended levels (6 to 130 mg of potassium iodate per kg of salt). Also, this test can be used to estimate approximately the level of iodine in a given sample of iodated salt, since the test reagents produce distinguishable gradations of grayish-blue colour, reflecting differences in the amount of iodine, over the range of concentrations recommended for iodine in iodated salt.

As illustrated in figure 1, the kit should be composed of; (a) tablets N and R; (b) plastic bottles (75 ml); (c) plastic dropper; (d) distilled water in a container (500 ml); (e) plastic spoon; (f) a white plastic plate with circular depressions; (9) a standard salt containing 15 ppm iodine (Kl or KlOa as the case may be); and (h) a chart for comparing the intensity of the colour.

The tablets can be directly dissolved in water. Table R contains a reagent to release iodine from iodate; tablet N consists of a soluble starch and an acidifying agent. Table 1 indicates the chemical composition of tablets N and R.

The iodate reagent can be prepared by dissolving one tablet of N and one tablet of R in 50 ml of distilled water in a plastic bottle. The reagent is stable for several hours under tropical conditions. To obtain more stable reagents, one tablet each of N and R can be separately dissolved in two bottles. The reagents prepared separately remain stable for several months.

Method

On the plastic plate, which has circular depressions to keep the sample separate and which should be carried in the kit, place a spoonful of salt to be tested and, in a separate depression on the plate, place a similar quantity of a standard salt. (A standard salt is one that contains 15 ppm of iodine, the minimum amount required by regulations.) Add two drops of the combined reagent (N+R) to both salt samples. If the N and R solutions are prepared separately, two drops of solution N followed by two drops of solution R can be added. The wet iodated standard salt will turn grayish-blue immediately and the colour will persist for several minutes before turning brown. If the salt sample being tested also turns grayishblue, the unknown sample is also iodated. Rough estimates of the amount of iodine present in the salt can be made on the basis of the colour intensity (fig. 1).

TABLE 1. Composition of the tablets used in the spot test for detecting iodinated salt

a. Oxalic, citric or sodium acid sulphate.

IODIDE TEST

The test described will detect the presence of iodide over the range of recommended levels of ionization (5 to 100 mg of potassium iodide per kg of salt). This test cannot be used to measure the relative degree of iodization because it produces a uniform deep-blue colour over the entire range of recommended concentrations.

The kit consists of:
1. Tablet S. which is made up of soluble starch, a reducing agent, and an acidifying agent (table 1).
2. The other materials are the same as for the iodate kit, but only one reagent bottle is necessary. The iodide reagent is prepared by dissolving one tablet of S in 50 ml of distilled water in a plastic bottle. This reagent is stable for a long time. The tablets should be kept dry before use.

Method

Place separately on the plastic plate a spoonful of the salt to be tested and a similar amount of standard salt with 15 ppm of iodine. Add two drops of the reagent to both portions of salt. The standard iodized salt will immediately turn blue and stay that colour for several minutes before turning grey, after which the colour fades rapidly. If the unknown salt being tested also turns blue, it is an iodized salt.

DISCUSSION

From our experience, it is possible to detect iodine levels as low as 1 ppm and as high as 100 ppm in salt containing iodate. When iodated salt is used one can differentiate, with the help of a colour chart, the grayish-blue colour obtained over a range of iodine concentrations of 1, 5, 10, 15, 20, 30, and 40 ppm.

In the kit we propose 50 ml of reagent can be used to test about 500 salt samples containing either iodate or iodide. We have observed in the course of testing our kit that boiled water (tap or well) can be used in place of distilled water for the preparation of the reagent solutions. The resulting solution is as potent and useful as the one prepared with distilled water. If distilled water is available in the field one can conveniently dispense with this in the kit. Plastic bottles are preferable to glass, which may be broken during transit.

COST

The cost of a kit consisting of three plastic bottles for reagent solutions, a dropper, a spoon, a plastic plate, and a distilled water bottle is about 2 rupees (US$0.20) in India. The cost of the iodate reagent is about 20 paise (US$0.02) and that of the iodide reagent about 15 paise (US$0.015).

REFERENCE

1. J. P. Dustin and J. P. Ecoffey, "A Field Test for Detecting Iodine-enriched Salt," Food Nutr. Bull., 5(4): 52-54(1983).

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