In addition to using synthetic vitamin C for direct supplementation, food manufacturers have used it for a variety of other purposes.
The usefulness of vitamin C in bread-making depends on its ability to modify the properties of wheat flour proteins in a technologically advantageous manner. As early as 1935, vitamin C was found to be as effective in improving flour as potassium bromate, while being nutritionally more acceptable. Flour improvers shorten the time required for flour to "age" after milling and the time that the mixture of dough and yeast requires for "ripening" before baking. Vitamin C acts as an oxidizing agent in the dough; it is oxidized to dehydroascorbic acid, which then participates in the oxidation of the wheat protein, gluten, to form cross-linkages. These stages are vital for a loaf to rise well and keep its texture after leaving the oven. There was considerable interest in flour improvers (Chamberlain, 1981) since, in order for bread to be mass-produced economically, it was necessary to shorten the production stages.
Treating fresh meat with a vitamin C solution delays the change of the fresh red appearance of meat to a less fresh-looking brown. This use is prohibited in some countries, e.g. the UK, as being "deceptive to the public", though it was claimed that the same result could be obtained by feeding animals a high level of vitamin C before slaughter. The vitamin is used in fresh sausages and as an additive in cured products (Ranken, 1981). The reason for curing meats is that they can then be stored, even without refrigeration, with little risk of infection by the highly pathogenic organisms of the Botulinus family in addition to developing an attractive characteristic pink colour. The traditional curing of meat involves pickling with a solution of salt and potassium nitrite. Since nitrosamines, which can be carcinogenic at very low concentrations, can be formed by nitrites, the food industry was under pressure to find ways of curing meat with lower nitrite levels. Vitamin C was found to be a useful additive for developing an attractive colour in cured meats having a lower nitrite content (Ranken, 1981).
Fruit juices and beverages
Fruits are an important source of vitamin C and fruit juices are a major contributor to vitamin C intake in Europe and North America. Vitamin C is often included in soft drink formulations, which serves to stabilize their quality, especially where colour and flavour are concerned. In certain instances the vitamin serves as an important processing acid, e.g. for removing oxygen from solutions in order to increase product shelf-life.
Oils and fats
Vitamin C is used as an antioxidant in oils and fats. Antioxidants prevent or retard oxidation, in particular the oxidative rancidity caused by atmospheric oxygen, and thus protect fats, carotenoids, vitamins A and D, and other nutritive ingredients. Many factors influence the antioxidant effectiveness of vitamin C, e.g. the specific content of metals, oxygen, and polyunsaturated lipids. In each case optimum vitamin C treatment has to be determined, in addition to the effects of physical conditions, packaging, water activity, etc. (Kläui,1979).
Vitamin C, which is itself insoluble in lipids, is added to oils and fats as ascorbyl palmitate (AP). Unfortunately, AP has a very slow dissolution rate in oils and fats at room temperature and in the end very little dissolves. AP is thus usually used in combination with products acting as solubilisers, but even then a fair dissolution rate is achieved only at high temperatures (Kläui, 1979). Efforts to overcome these drawbacks led to the development of a special application form where AP is pre-dissolved in lecithin, thus making it significantly easier to dissolve in lipid systems. Two commercial antioxidant mixtures containing BHA (butylated hydroxy anisole) and BHT (butylated hydroxy toluene)-but rarely AP-are added to vegetable oils (P. Ryffel, Roche, personal communication).
It has been suggested that since dehydroascorbic acid is more fat-soluble than ascorbic acid, in addition to exhibiting biological vitamin C activity, it might show advantages in certain systems.
The fortification of food-the enrichment of commonly consumed foods with micronutrients in order to improve the nutritional quality of the diet-is increasingly used for novel food products that are marketed to replace traditional diets. The increasing use of refined foods in industrialized countries, and the introduction of engineered foods that are formulated from highly purified ingredients, can contribute to micronutrient deficiencies if not adequately upgraded, e.g. margarine with vitamins A and D and cereal products with vitamins B1, B2, niacin and iron.
Items regularly fortified with vitamin C in several countries, especially in Europe and North America, include various bottled beverages as well as instant drinks, milk, and baby foods. "Protein treats"-solid bars with a chocolate-like texture that are simpler to manufacture than chocolate, and various types of candy bars-can be enriched with vitamin C. All these products have a long shelf life and packing and transport present no special problems. Several types of biscuits, including simple biscuits or sandwich biscuits with a soft filling, are vitamin C-fortified. Vitamin C is more stable in biscuits with a soft filling but their shelf life is shorter (P. Ryffel, Roche, personal communication). Other products like dry instant soup mixes are relatively easy to manufacture, transport and prepare. Fortified instant soup mixes have been used for school children in the former Yugoslavia during the late winter and early spring months when dietary intakes of the vitamin were low. Vitamin C in the form of a premix has been added to meals during their preparation in kindergartens, schools, industrial canteens, hospitals, and homes for the elderly. In some of these same settings vitamin C powder has also been added to water before drinking (Buzina, personal communication).