It can be assumed that oil in the general ration is consumed by all family members. Vitamin C (ascorbic acid) is not soluble in oil. However, there are various oil-soluble derivatives of the vitamin, the most common being ascorbyl palmitate. Chemically it is an ester of ascorbic acid with the fatty acid being palmitic acid. It is very soluble in alcohol (10 g/100 ml) but has a low solubility and poor rate of dissolution in oil (30 mg/100 ml at room temperature). Forty-one percent of ascorbyl palmitate is ascorbic acid and thus oil that is fully saturated with ascorbyl palmitate would provide only 12 mg vitamin C per 100 ml of oil. A daily ration of 20 ml of oil would contribute 2.5 mg vitamin C, which does not include losses occurring during storage and preparation. This extremely low amount of vitamin C would not cover minimal requirements to prevent the onset of scurvy.
As Rivers (communication to UNHCR, 1988), has observed, with regard to fortification of oil with vitamin C:
• Ascorbyl palmitate supplementation would not prevent scurvy but would delay the onset of the disease, which would provide more time for other interventions to be put in place.
• 80 ml of fortified oil per day could prevent scurvy.
Harrell-Bond et al. (1989) suggested that ascorbyl palmitate would be a suitable derivative of vitamin C for the fortification of oil and skimmed milk powder, and that these fortification possibilities should be seriously considered by international agencies responsible for feeding refugees.
Ascorbyl palmitate is used as an antioxidant by the food industry. Also, tocopherol (vitamin E) is usually added, thereby increasing the anti-oxidative effect of the components and allowing the amount oxidised to be reduced. The result is that the antiscorbutic properties of ascorbyl palmitate are protected to a large degree. Many foods, especially those of vegetable origin, contain tocopherols and ascorbic acid as natural antioxidants.
The low solubility and poor rate of dissolution of ascorbyl palmitate have led to the development of special commercial products. Roche has developed a form in which ascorbyl palmitate has been pre-dissolved in lecithin. In this "solubilized" state, ascorbyl palmitate is significantly easier to dissolve in oil, e.g. 300 mg ascorbyl palmitate takes 90 seconds to dissolve in 1 litre of oil at 110°C, whereas the same amount of ascorbyl palmitate in the form of the antioxidant mixture takes 90 seconds to dissolve at a much lower temperature (45°C).
Ascorbyl palmitate is stable as a solid, in crystalline form, as well as in the concentrated solubilized form of the antioxidant mixture. During storage of highly diluted oil there is a continuous decrease of ascorbyl palmitate content and the oil should not be heated to temperatures above 105°C under atmospheric conditions and in the presence of oxygen. However, the antioxidant mixture seems not to be the appropriate method for vitamin fortification since 75% of the product is lecithin and only 40% of the ascorbyl palmitate, which makes up 25% of the mixture, is vitamin C. The advantage of the 200-300 ppm of vitamin C present is therefore minimal. It is also very expensive (¡ÓUS$ 54/kg) compared to vitamin C powder (¡ÓUS$ 13.50/kg). In addition, when 500 mg per litre is dissolved in oil a slight metallic taste develops (Roche, personal communication).
Rivers (communication to UNHCR, 1988) suggested a second approach to fortifying oil with vitamin C: disperse vitamin C, or a derivative, in the oil thereby creating a suspension rather than a solution. He tried making suspensions of both finely powdered ascorbic acid, which is commercially available, and ascorbyl palmitate and found that stirring finely powdered vitamin C into oil gave a suspension which took more than 24 hours to clear. His observation was that 20 ml of oil contained at least 30 mg of vitamin C for 24 hours. The exact concentration thus depends on when the vitamin C is added to the oil, when the oil is distributed, and when it is consumed. However, it can be concluded that the amount of vitamin C consumed by using oil as a vehicle would not cover the requirements necessary to prevent scurvy. Ryffel (Roche, personal communication) states that oil is not an ideal vehicle for vitamin C because of problems of low solubility.
It has been suggested that "micro-encapsulation" of vitamin C in vegetable oil should be a subject for operational research with oil possibly serving as the vehicle for larger amounts of vitamin C. However, discussions with Roche showed that the technology of micro-encapsulation to stabilise vitamin C in oil is not cost-effective. The fat-coated forms of vitamin C are 2-3 times the price of regular vitamin C and a special coating can cost even 3-6 times as much. Coated forms protect the vitamin and therefore increase its stability, though not its solubility, in oil. In addition, too much coating could decrease the vitamin's bioavailability.