Ascorbic Acid (Vitamin C)

Grades and forms

Ascorbic acid is L-ascorbic acid, the reference form of vitamin C. Its mass equals the vitamin C declared on the label. One milligram of ascorbic acid counts as one milligram of vitamin C before any overage, so no conversion factor applies. The vitamin C guide compares all the forms.

Ascorbic acid powder is bought in bulk in three main physical forms:

• Crystalline or fine powder: for powder blends, sachets, capsules and effervescent formulations.
• Granulated grades: ascorbic acid granulated with a binder so that it compresses directly into tablets.
• Coated grades: particles with a fat or cellulose coating that slows contact with moisture and reactive ingredients.

Granulated and coated grades contain a share of binder or coating. Their ascorbic acid content is therefore lower than that of the crystalline material. Base label arithmetic on the assay stated on the certificate of analysis, not on a nominal figure.

Three points usually decide the grade: the format and process, the specification standard your customer requires, and whether the blend contains reactive ingredients such as metal salts. SoleChem supplies ascorbic acid from stock in its warehouses in Italy and Spain. It sends the specification sheet and certificate of analysis with the quote. State the physical form and specification standard you need in the quote form.

EU regulatory status

• Food supplements: L-ascorbic acid is a permitted vitamin C source in Annex II of Directive 2002/46/EC. Vitamin C appears in Annex I and is declared in mg. The guide to permitted forms covers the full list.
• Maximum amounts: EU-wide maximum amounts of vitamin C in food supplements have not been set. Member states apply their own limits, which differ. See maximum levels by EU country.
• Food additive: ascorbic acid is authorised as E300 under Regulation (EC) No 1333/2008. Its purity criteria are in Regulation (EU) No 231/2012.

The additive rules apply when ascorbic acid performs a technological function, such as protecting an oil from oxidation. Regulation (EC) No 1333/2008 is generally read as not applying to substances added as nutrients unless they are used as food additives (see its Article 2(2)). The role in your formula therefore decides how it is labelled. For authorised claim wording, consult the EU Register of nutrition and health claims and the health-claims guide.

Formulation notes

Stability. Ascorbic acid oxidises in the presence of moisture, oxygen, heat and light. Trace copper and iron ions accelerate the reaction. Degradation shows as yellow to brown discolouration. Dry crystalline material is far more stable than ascorbic acid in solution.

Overage. Because of this sensitivity, vitamin C formulations commonly carry an overage. Set it from stability data on your own product, not from a general rule. The overage calculator does the arithmetic.

Tablets. Fine crystalline ascorbic acid compresses poorly. Granulated grades are the usual choice for direct compression in tablets. Keep humidity low during manufacture and use moisture-protective packaging.

Effervescent tablets. Ascorbic acid can serve as the acid component that reacts with sodium bicarbonate. That reaction starts with moisture, so effervescent tablets need dry raw materials and low-humidity processing.

Taste. The acid taste is sharp. In chewable tablets, gummies and powders for neutral drinks, formulators often switch to sodium or calcium ascorbate.

Compatibility. Ascorbic acid is a reducing agent and reduces ferric iron to ferrous iron. In liquid or high-moisture premixes it can degrade cyanocobalamin. Separate it from metal salts and sensitive vitamins, or use a coated grade, and confirm the result by stability testing.

Ascorbic acid compared with other forms

Ascorbate salts deliver less vitamin C per gram than ascorbic acid. The figures below are calculated from the molar masses: 176.12 g/mol for ascorbic acid, 198.11 g/mol for sodium ascorbate and 426.34 g/mol for calcium ascorbate. The calcium ascorbate figure assumes two ascorbate units per formula unit.

These masses exclude overage and assume material at 100 % assay. The salts also add sodium or calcium to the formula. Account for that mineral contribution in the formula and on the label where it is declared.