Micronutrient Premix is particularly a complicated commodity. Vitamins and minerals are made using various chemical compounds with different nutritional properties; the quality can vary tremendously and relatively sophisticated equipment and expertise are required to verify the quality of the premix produced.
To design and produce a high-quality premix you must have the knowledge of RDA (Recommended Dietary Allowance) values, the functionality of ingredients, interactions between ingredients, and nutrient physical characteristics.
Choosing the appropriate form of fortificant is important to minimize nutrient-nutrient as well as nutrient-food interactions and any resulting adverse effects. Iron, for example, is a difficult mineral to add to foods as the most bioavailable forms tend to promote fat oxidation resulting in the development of unacceptable sensory changes in the finished food.
The stability of vitamins is affected by a number of factors, such as temperature, moisture, oxygen, light, pH, minerals (especially iron and copper), vitamin-vitamin interactions, and other food components. Vitamin stability is affected most by heat, moisture, pH, and light, but given their chemical heterogeneity, vitamin losses in different foods vary considerably during both processing and storage of the final product. The most unstable vitamins are C, A, D, B1, and B12. Because of their multiple oxidation states, the presence of metal ions (iron and copper) accelerates the degradation of vitamins, especially vitamins C, A, and B1.
Fortification with several vitamins may give rise to vitamin-vitamin interactions that may accelerate the rate of breakdown of some vitamins; the best-known interactions are those among vitamins C, B1, B2, B12, and folic acid. The extent of these interactions is also dependent on the nature of the food product as well as on temperature, moisture level, pH, light, etc. during processing and storage.
Importance of Overages
To maintain the micronutrient levels declared on the product label throughout a product’s shelf life, the amount of vitamins added during processing needs to be higher than the levels reported on the label. The difference between the declared and formulated vitamin levels, termed “overage,” will be different for each food application. Vitamin overages are normally calculated as a percentage of the declared level:
Overage = (formulated vitamin level – declared level)/ declared level × 100.
Micronutrient bioavailability and organoleptic quality of fortified foods
The nature of the food or beverage vector will have considerable bearing on the fortification since organoleptic alterations caused by certain added micronutrients must be dealt with quite often.
The bioavailability of added micronutrients, especially minerals and trace elements, must also be taken into consideration. In these two respects, iron is undoubtedly the most difficult micronutrient to add to food, yet iron deficiency is the most widespread micronutrient deficiency in the world today. The choice of an iron-fortification compound depends primarily on the nature of the food itself, and is nearly always a compromise between maximal bioavailability and minimal organoleptic alteration. Soluble iron compounds such as ferrous sulphate are very well absorbed but can give rise to unacceptable colour and taste changes in some products.
In many cases, it is possible to improve the bioavailability of iron from foods by the addition of an appropriate amount of ascorbic acid. A molar ratio of ascorbic acid to iron of 2:1 often significantly enhances iron absorption, but the optimal ratio depends on the nature of the food or beverage, and especially on the levels of other enhancers and inhibitors of iron absorption in the product.
Mineral interactions and bioavailability
Interactions between minerals can also have implications for mineral bioavailability in multiply fortified products. Iron, zinc, and calcium have been the most studied in this respect. For example, in the absence of phytic acid, the effect of calcium on zinc absorption is low. However, when phytic acid is present, calcium significantly inhibits zinc absorption. Likewise, oral iron supplements significantly inhibit inorganic zinc retention when consumed simultaneously at iron-to-zinc ratios as low as 1:1 .
Designing micronutrient premixes
Once the appropriate application for fortification has been identified, the next step is to design the micronutrient premix(es), as a function of the:
» micronutrient requirements and status of the target consumer,
» micronutrient levels in the raw materials to be used,
» estimated processing and storage losses (as above),
» expected homogeneity of mixing.
For fortifying with both minerals and vitamins, two premixes are generally used, one for minerals and another for vitamins, in order to minimize metal-catalysed degradation of vitamins during storage of the premix. Usually, a small quantity of the premixes is sent to the customers for preliminary, small-scale production trials. Complete micronutrient analyses of these trial products are then carried out to calculate the final specifications of the premixes.
Quality control in food fortification
Fortification of staple or processed foods requires properly designed and resourced quality control systems. Neither government legislation nor industrial specifications for food fortification will be effective without adequate quality control, both at the production site and in central laboratories. Reliable quality control of the addition of micronutrients to foods can only be obtained by the careful use of appropriate and validated analytical techniques in the hands of trained analysts. Validation of analytical methods involves the establishment of performance characteristics such as specificity, sensitivity, working concentration range, the limit of detection, the limit of quantitation, ruggedness, accuracy, and precision.
The production of quality premix thus deserves careful and professional attention. Product quality must be built into and not merely tested in the product.
Monitoring of all the critical points affecting the quality of premix is the best solution for minimizing the deviations from standards. It is only through well-organized, adequately staffed, and accurately performed process and formulation controls that a desired quality of the premix may be achieved.
- Denis Barcl, Multiple fortifications of beverages – SAGE Journals
- WHO – Guidelines on food fortification with micronutrients