Vitamin A – increase nutrition value of a product (part 2). The food fortification.

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As mentioned in part 1 of Vitamin A – increase nutrition value of a product, Retinol and other forms of Vitamin A are fat-soluble vitaminers important in vision, immune system and bone growth. They belong to the family of chemical compounds known as Retinoids (or diterpenoids). Primary Vitamin A forms available in the industry for the food fortification are:

  • Retinol (animal sources or synthetic),
  • Retinyl Acetate,
  • Retinyl Palmitate,
  • Carotenoids (plant sources or synthetic), mainly Carotene.

Chemical Properties

Many different geometric isomers of Retinol, Retinal and Retinoic Acid are possible as a result of either a trans or cis configuration of four of the five double bonds found in the polyene chain. The cis isomers are less stable and can readily convert to the all-trans configuration. Nevertheless, some cis isomers are found naturally and carry out essential functions. For example, the 11-cis-Retinal isomer is the chromophore of rhodopsin, a photoreceptor molecule. Rhodopsin is comprised of the 11-cis-Retinal covalently linked via a Schiff base to the opsin protein (either rod opsin or blue, red or green cone opsins). The process of vision relies on the light-induced isomerisation of the chromophore (means Retinal) from 11-cis to all-trans resulting in a change of the conformation and activation of the photoreceptor molecule. Let’s look at chemical structures of A Vitaminers.

Retinol

Retinyl Esters

Beta-Carotene

Besides, all-trans and 11-cis isomers in the body are also present other structural isomers of Vitamin A like 9-cis and 13-cis.

Because all A Vitamers have different chemical structures they have also different properties, which can have an influence on the food composition. For example, a colour of Retinol or esters is yellow, where a colour of Carotenoids, and mainly used as food additive beta-Carotene, is red. Also, lipophilicity is increasing in order: Retinol, Retinyl Acetate, Retinyl Palmitate, Beta-Carotene.

Available forms of Vitamin A.

Vitamin A for the food fortification or for supplements manufacturing is used mostly in the form of all-trans-Retinyl Acetate or all-trans-Retinyl Palmitate. These 2 forms of Vitamin A are the most stable and its use is convenient. Vitamin A can be also added in form of pro-Vitamin A as synthetic all-trans-beta-Carotene or a natural mix of carotenoids containing mainly beta- and alpha-Carotenes.

Retinyl Acetate and Retinyl Palmitate are in the form of crystals or oily solutions, as well as, dry free flowing powders (spray-dried on a carrier or encapsulated). Similar beta-Carotene or mixed carotenoids are available as oily dispersions or powders. Powdered forms of Vitamin A are dispersible in water, so they can be used in aqueous solutions. We have to be careful to work at neutral pH to avoid esters hydrolysis during the food composition. Vitamin A in powdered form is easily used in dry products as well.

Pure forms of Vitamin A are sensitive to light and can undergo oxidation at elevated temperatures. High quality encapsulated Vitamin A is protected from outside conditions and is more stable.

Supplements and fortified food - Regulatory Guidance

Vitamin A is essential for a proper development and functioning of a human body at any age.

Its content in the food is regulated from Infant Milk formulas to any food products and supplements. Allowed amounts of Vitamin A in Infant Milk formulas depend on the world region and regulating entity.

Allowed amounts of Vitamin A in Infant Formulae

Very often ordinary food for children and adults is fortified with Vitamin A. For example, Retinyl Palmitate is commonly added to reduced-fat milk (however, we have to consider amount zinc in the product, because Retinyl Palmitate reacts with zinc and protein to form an unabsorbable complex). Vitamin A is also present in typical diet supplements. Many of multivitamin supplements for adults typically contain 2,500–10,000 IU of Vitamin A, often in the form of both Retinol and beta-Carotene.

Vitamin A can be taken also in both oral and injectable forms, especially during treatment of Vitamin A deficiency.

Food composition and fortification

A process of the food fortification with Vitamin A depends on the food matrix. Let’s look at some examples.

Vegetable oils are ideal matrixes for Vitamin A addition in a form of Retinyl Palmitate or Retinyl Acetate. The methods for fortifying vegetable oils are well established, fairly simple and easy to implement at low cost. Furthermore, oils stabilize Vitamin A and delay destructive reaction of oxidation. It is recommended that at least 18 mg of Vitamin A is added per kilogram of vegetable oil (in the US). The cost of fortification is about $2.00 per metric tonne (MT) of oil (Johnson, L. E. (1997) Oils, fats and margarine: overview of technology. Food Fortification to End Micronutrient Malnutrition).

Margarine and other hydrogenated oil products, as well as, butter (which contains also natural Vitamin A from milk) are also one of the most suitable vehicles for vitamin A. Nowadays, Vitamin A is already added to margarine in many countries to imitate the nutritional value of butter. Usually, margarine is fortified at levels ranging from 1 to 15 mg/kg, which provides 2–40% of the RDI, assuming a daily consumption of 15 g (Solon, F. S. (1997) A case report on the fortification of margarine with vitamin A: The Philippine experience. Food Fortification to End Micronutrient Malnutrition, Sridhar, K. K. (1997) Tackling micronutrient malnutrition: two case studies in India. Food Fortification to End Micronutrient Malnutrition). Vitamin A fortification of margarine was initiated in Denmark in the 1920s, when cases of nutritional blindness appeared after butter was replaced with nonfortified margarine (Bloch, C. E. (1931) Effects of deficiency in vitamins in infancy. Am. J. Dis. Child. 42:271). The cost is similar to that of oil fortification.

Fortification of cereal flours and meals with Vitamin A is well known. Spray dried Retinyl esters used in such products are usually quite stable (loss not exceeded 50%) (SUSTAIN (1999) The progress of wheat flour fortification with vitamin A in the Philippines.). There is often no need for changes in a flour manufacturing because cereal flour production usually incorporates enzymes, oxidants and other substances. In Venezuela the flour is fortified with vitamin A at 2.7 mg/kg, which contributes at ∼30% of the Vitamin A RDI, assuming a consumption of 80 g/day and 15% losses of the Vitamin A during production, handling and storage of the flour (Chavez, J. F. (1997) Enrichment of precooked corn flour and wheat flour in Venezuela: a successful experience. Food Fortification to End Micronutrient Malnutrition). A cost of fortification in 2002 was about US$1.40/MT, which was about 0.35% of the purchase price of flour. Today spray dried forms of Vitamin A are more popular, so also cheaper.

The Vitamin A compound that is used for sugar or sugar-based products fortification is Retinyl ester in form of a gelatine-base beadlets, which is bound to the sugar crystal through a layer of vegetable oil to avoid segregation (Dary, O. (1994) Advances in the process of fortification of sugar with vitamin A in Central America. Bol. Oficina Sanit. Panam. 117:529-537). Vitamin A in encapsulated form is stable and protected from light and oxidation. The cost of fortification to the industry amounts to $9.18 per MT (Mora, J. O., Dary, O., Chinchilla, D. & Arroyave, G. (2000) Sugar fortification with vitamin A: a Central American contribution to the developing world. Vitamin A Sugar Fortification in Central America: Experience and Lessons Learned, MOST/U.S. Agency for International Development Arlington, VA), which represents about 2% of the retail price of sugar.

The use of Vitamin A as beadlets is sometimes problematic. In this form, Vitamin A has been used to fortify of Monosodium glutamate. This ingredient is a free flowing white powder and Vitamin A in a form of yellow beadlets is not fully compatible. A solution, in this case, is adding spray dried (unfortunately also yellowish) form of Vitamin A in a smaller amount (Muhilal, A., Murdiana, A., Azis, I., Saidin, S., Jahari, A. B. & Karyadi, D. (1988) Vitamin A fortified monosodium glutamate and vitamin A status: a controlled field trial. Am. J. Clin. Nutr. 48:1265-1270).

Fortification with Vitamin A is also practiced during whole-wheat grain, tea, instant noodles, fish sauce, yoghurt and salt production. Fortification of rice has been tried by coating (Rubin, S. H., Emodi, A. & Scialpi, L. (1977) Micronutrient additions to cereal grain products. Cereal Chem. 54:895-904) or introducing the nutrients into artificial kernels, as a new technology known as Ultra-Rice (Lotfi, M. & Britton, M. D. (1997) Rice fortification: a promising technology for micronutrient deficiency reduction). Unfortunately, during use of the Ultra-Rice process, significant losses of Vitamin A has been reported (Murphy, P. A. (1996) Technology of vitamin A fortified foods in developing countries. Food Technol. 50:69-74, Flores, H., Guerra, N. B., Cavalcanti, A. C. A., Campos, F. A. C. S., Azevedo, M. C. & Silva, B. M. (1994) Bioavailability of vitamin A in a synthetic rice premix. J. Food Sci. 59:371-372).

During compose of fortified food, we have to remember about protecting Vitamin A from oxidation, which is intensified by an influence of light and elevated temperature. The best solution to solve this issue is adding vitamin E to oily formulations and vitamin C to wet or aqueous products. Remember also about absorption and bioavailability of Vitamin A. For example, as mentioned above, in the intestine Vitamin A is protected by Vitamin E, so a lack of Vitamin E in food composition is not a good idea. Be sure also, that fat soluble Carotenes, as pro-Vitamin A, are used in oily formulations for example with olive oil. They have to be solubilised to be bioavailable.

Another aspect to be considered is the stability and the cost of different industrial forms of Vitamin A. Vitamin A additives (free-flowing powders) needed for a fortification of dry matrixes (e.g., flour and sugar) are at least four times more expensive than the oily forms. Also, a stability of Vitamin A spray-dried on a carrier is inferior.

Correct labelling of the food products is also very important. During the food fortification or dietary supplements manufacturing, we have to remember to correctly calculate and provide on a label all of Vitamin A compounds (preformed Vitamin A) as Retinol Equivalent (and pro-Vitamin A in the same way). In cases, where preformed Vitamin A and pro-Vitamin A have been used, the percentage of Retinol or Retinyl Esters in the supplement should be used to determine whether an individual's Vitamin A intake exceeds the Upper Limits. For example, a supplement labelled as containing 10,000 IU of Vitamin A with 60% from beta-Carotene (and therefore 40% from Retinol or Retinyl ester) provides 4,000 IU of preformed Vitamin A. That amount is above the Upper Limit for children from birth to 13 years but below the Upper Limit for adolescents and adults.

I hope this article gave you an overview of Vitamin A and fortification food with it. If you have any questions please do not hesitate to contact me at the IngredientsHub.com.

For more information, you can review EU Directive 2006/37/EC and EU Regulation 1170/2009/EC, US FDA Food Guidance Documents or read Guidelines on food fortification with micronutrients.