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TABLE 5. Acceptability of double-fortified salt in foods (mean scores assigned to foods prepared with double-fortified salt)
| Colour | Appearance | Texture | Flavour | Taste | Overall quality | |||||||
| Food item | CS | DFS | CS | DFS | CS | DFS | CS | DFS | CS | DFS | CS | DFS |
| Chapati | 4.6 | 4.7 | 4.6 | 4.7 | 4.5 | 4.6 | 4.1 | 4.2 | 4.3 | 4.4 | 4.8 | 4.9 |
| Lemon rice | 4.9 | 4.9 | 4.8 | 4.7 | 4.3 | 4.4 | 4.5 | 4.5 | 4.2 | 4.2 | 4.5 | 4.6 |
| Coconut rice | 4.8 | 4.9 | 4.2 | 4.3 | 4.1 | 4.0 | 4.3 | 4.2 | 4.8 | 4.9 | 4.9 | 4.7 |
| Dal | 4.7 | 4.5 | 4.5 | 4.6 | 4.4 | 4.6 | 4.7 | 4.7 | 4.7 | 4.6 | 4.6 | 4.5 |
| Chatni | 4.1 | 4.2 | 4.4 | 4.5 | 4.5 | 4.3 | 4.1 | 4.2 | 4.5 | 4.8 | 4.5 | 4.6 |
| Potato curry | 4.3 | 4.4 | 4.1 | 4.0 | 4.4 | 4.5 | 4.0 | 4.1 | 4.6 | 4.4 | 4.7 | 4.6 |
| Vegetable curry | 4.1 | 4.0 | 4.3 | 4.2 | 4.0 | 4.1 | 4.6 | 4.5 | 4.8 | 4.9 | 4.6 | 4.7 |
| Idli | 4.9 | 4.9 | 4.8 | 4.8 | 4.9 | 4.9 | 4.0 | 4.1 | 4.9 | 4.9 | 4.8 | 4.9 |
| Dosa | 4.5 | 4.6 | 4.1 | 4.3 | 4.5 | 4.4 | 4.3 | 4.1 | 4.7 | 4.8 | 4.9 | 4.9 |
| Upama | 4.8 | 4.9 | 4.7 | 4.6 | 4.1 | 4.3 | 4.6 | 4.6 | 4.6 | 4.7 | 4.7 | 4.8 |
| pongal | 4.7 | 4.6 | 4.3 | 4.5 | 4.4 | 4.6 | 3.9 | 3.8 | 4.1 | 4.3 | 4.0 | 4.1 |
| Vada | 4.3 | 4.5 | 4.9 | 4.8 | 4.7 | 4.9 | 4.3 | 4.4 | 4.8 | 4.9 | 4.7 | 4.8 |
| Puri | 4.1 | 4.0 | 4.7 | 4.8 | 4.5 | 4.7 | 3.8 | 3.9 | 4.5 | 4.6 | 4.6 | 4.5 |
| Pakodi | 4.3 | 4.4 | 4.9 | 4.8 | 4.1 | 4.3 | 4.9 | 4.9 | 4.7 | 4.8 | 4.9 | 5.0 |
| Bajji | 4.5 | 4.3 | 4.1 | 4.2 | 4.1 | 4.0 | 3.9 | 4.0 | 4.4 | 4.3 | 4.3 | 4.2 |
| Salad (vegetable) | 4.9 | 4.9 | 4.8 | 4.8 | 4.9 | 4.9 | 4.7 | 4.8 | 4.9 | 4.9 | 4.9 | 5.0 |
| Lemon juice | 4.7 | 4.8 | 4.1 | 4.0 | 4.8 | 4.8 | 3.9 | 4.1 | 4.7 | 4.8 | 4.6 | 4.5 |
| Curd | 5.0 | 5.0 | 4.9 | 4.9 | 4.7 | 4.6 | 3.8 | 3.9 | 4.6 | 4.5 | 4.4 | 4.4 |
| Fruits | 4.8 | 4.9 | 4.3 | 4.4 | 4.5 | 4.5 | 4.7 | 4.7 | 4.7 | 4.9 | 4.8 | 4.9 |
| Pickles | 4.3 | 4.4 | 4.6 | 4.5 | 4.9 | 4.8 | 4.1 | 4.2 | 4.3 | 4.5 | 4.5 | 4.6 |
| Sambar | 4.1 | 4.3 | 4.4 | 4.3 | 4.1 | 4.4 | 4.5 | 4.7 | 4.6 | 4.8 | 4.3 | 4.4 |
| Rasam | 4.3 | 4.4 | 4.1 | 4.1 | 4.0 | 4.2 | 4.8 | 4.6 | 4.3 | 4.5 | 4.8 | 4.7 |
| Egg (omelette) | 3.9 | 3.8 | 4.3 | 4.4 | 4.5 | 4.6 | 4.1 | 4.0 | 4.0 | 4.2 | 4.3 | 4.2 |
| Fish | 4.1 | 4.2 | 4.0 | 4.1 | 4.3 | 4.2 | 4.4 | 4.3 | 4.1 | 4.4 | 4.2 | 4.3 |
| Mutton | 4.3 | 4.2 | 4.1 | 4.0 | 4.5 | 4.4 | 4.1 | 4.2 | 4.0 | 4.3 | 4.1 | 4.0 |
CS, Common salt; DFS, double-fortified salt.
Transportation of double-fortified salt
Transportation of double-fortified salt produced by dry mixing by road to urban and rural areas was feasible and resulted in no iodine loss. The iodine and iron concentrations remained at their initial levels of 40 and 1,000 ppm, respectively. Storage at ambient temperature in the household did not affect the concentrations. No loss of either iodine or iron was observed after six months.
Acceptability trials
The results showed no change in the organoleptic properties of foods prepared with double-fortified salt based on scores given by volunteers (table 5). Its use was not associated with any change in the sensory features of the food items. The salt was well accepted in day-to-day cooking, with no complaints regarding the foods prepared with it.
Discussion
The common salt produced in India contains amounts of moisture and magnesium impurities [10] that adversely influence the stability of iodine compounds added to it (table 6). Although calcium carbonate enhanced the shelf-life of iodized salt [11], it did not do so for double-fortified salt [7]. When spray mixing was employed for the large-scale production of double-fortified salt either by continuous production or by batch mixing, most of the iodine (95%98%) was lost during blending in the ribbon blender.
In the spray-mixing process, ferrous sulphate undergoes hydrolysis when dissolved in water, and because of the acidic nature of the solution formed, the levels of KIO3 and KI are reduced, leading to the liberation of iodine. The magnesium impurities present in common salt aggravate the iodine loss because of their hydroscopic nature. Furthermore, moisture accelerates the oxidation of ferrous iron to the ferric form, which is coloured, and hence the double-fortified salt is discoloured despite the quality of common salt used for double fortification. Thus the spraymixing process had several problems and was unsuitable for fortifying salt with iron and iodine. This is in line with earlier observations of iron-fortified salt [5].
On the other hand, stickiness, discolouration, and other operational problems did not occur with the dry-mixing process. Because SHMP has more affinity for moisture, it prevents the interaction of ferrous sulphate with moisture. Therefore, the hydrolysis and oxidation of ferrous sulphate are prevented. The double-fortified salt produced by dry mixing was free of problems, satisfactory, and cost effective, as the cost of production was reduced by 14% compared with spray mixing. Similar observations were reported for the large-scale production of ironfortified salt in factories [6].
Based on the results of laboratory studies reported earlier, the production of double-fortified salt does not require refined or dried salt [7]. However, our experience showed that it is difficult to ensure iodine stability in salt fortified with iron and iodine if the moisture content is more than 2% and the magnesium content exceeds 0.1%. When we used common salt with varying levels of moisture and magnesium, the iodine loss was proportional to increases in moisture and magnesium content. Others reported similar observations [12].
On the basis of these trials, it is suggested that a good-quality common salt be used for double fortification (table 7). The pH of a 5% aqueous solution of the common salt must be close to 7.
It is desirable to pack the double-fortified salt in 0.5-kg or 1-kg retail HDPE packets. The production cost in the factory is US$80 per metric ton, of which 45% is for common salt, 22% for chemicals, and 33% for operating costs. However, the price of doublefortified salt at the consumer level is US$130 per metric ton due to the cost of 1-kg HDPE packets (US$20) and other overhead (US$30), including the profit margin at various outlets.
The results of our acceptability trials were satisfactory and in good agreement with similar studies [5-7] on iodinefortified salt. Thus, we have demonstrated the successful production of double-fortified salt at the factory level in India using a dry-mixing process.
TABLE 6. Composition of edible salt produced in India
| Composition | % |
| Sodium chloride | 95 98 |
| Magnesium chloride | 0.5-2.0 |
| Calcium | 0 3 1.2 |
| Sulphate | 0.3 1.5 |
| Insolubles | 0.1-1.9 |
| Moisture | 2-6 |
TABLE 7. Suggested composition of common salt for simultaneous fortification with iodine and iron
| Constituent | Weight % (dry basis) |
| Sodium chloride | Not less than 99% |
| Magnesium salts | Not more than 0.05% |
| Calcium salts | Not more than 0.10% |
| Sulphate | Not more than 0.40% |
| Insolubles | Not more than 0.15% |
| Moisture | Not more than 1.5% |
Acknowledgements
The authors thank the officials of the Valinokkam and Hyderabad factories for their cooperation during this study. The secretarial assistance of Ms. Shakila Banu in the preparation of the manuscript is appreciated.
References
1. WHO. Diet, nutrition and the prevention of chronic diseases: iron deficiency. Report of a WHO study group. Technical Report 797. Geneva: World Health Organization, 1990:23-5.
2. Working Group on Fortification of Common Salt with Iron. Report. Am J Clin Nutr 1982;35:1442-51.
3. Status Report on the National iodine Deficiency Disorders Control Programme (NIDDCP). Policy and Advocacy Meeting on iodine Deficiency Disorders (IDD) 17 January 1992. New Delhi: NIDDCP, 1992.
4. The Salt Department. Universalisation of access to iodised salt-a mid-decade goal. New Delhi: Ministry of Industry, Government of India, January 1994.
5. Ranganathan S. Fortification of common salt with iron: use of polyphosphate stabilisers. Food Chem 1992;45: 263-7
6. Ranganathan S, Dillikumar PK, Ramamoorthy P. Reddy V. Large scale production of iron fortified salt. J Food Sci Tech 1993;30:166-8.
7. Narasinga Rao BS. Fortification of salt with iron and iodine to control anaemia and goitre: development of a new formula with good stability and bioavailability of iron and iodine. Food Nutr Bull 1994;15:32-9.
8. Wong SY. Hawk's physiological chemistry. 14th ed. New York: McGraw-Hill, 1965:1094.
9. Kolthoff IM, Belcher R. Volumetric analysis. Vol. III: Titration methods. New York: Interscience Publishers, 1957:246-7.
10. Report of the Working Group on Salt Industry. Jaipur: Goverment of India, Salt Commission, 1984:43.
11. Ranganathan S, Narasinga Rao BS. Stability of iodine in iodized salt. Ind Food Indust 1986;5:122-4.
12. Venkatesh Mannar MG, Jayapal S, Pandav CS. Double fortification of salt with iron and iodine. In: Young KW, Cha LY, Yull LK, Soon JJ, He KS, eds. Proceedings of the 14th International Congress of Nutrition, 20-25 August 1989. Seoul: Ewha Women's University, 1989: 1035-7