Ascorbic acid does two unrelated jobs in flour and bread, and buyers often conflate them. As a dough oxidant it strengthens gluten and improves loaf volume at doses measured in tens of parts per million. As a nutrient additive it restores vitamin C lost in milling, at doses set by food law. The two uses have different dosing, different specifications and different points in the process – and both are reasons the granulated 90% grade exists.
Job one: dough conditioning
In bakery, ascorbic acid is the oxidising agent of choice following the withdrawal of bromate in most markets. It is not an oxidant itself in the mixer – it is oxidised to dehydroascorbic acid by the ascorbate oxidase naturally present in flour, and that intermediate oxidises glutathione and protein thiol groups, which lets the gluten network develop. The consequence is a drier, more extensible dough with better gas retention.
| Parameter | Typical practice | What happens if it is wrong |
|---|---|---|
| Dose | Of the order of 20-100 ppm on flour weight, adjusted to the flour’s own strength | Under-dosed: slack dough, poor volume. Over-dosed: tight, short dough that tears during proving |
| Flour natural variation | Response depends on the flour’s ash, protein and endogenous ascorbate oxidase | The same dose behaves differently between flour streams – always trial on the actual flour |
| Point of addition | Dry-blended into the flour or into the premix before the mixer | Added late or unevenly, it acts locally instead of through the dough |
| Interaction with other agents | Works alongside emulsifiers, enzymes and reducing agents | Combining with a reducing agent without rebalancing gives an inconsistent dough |
| Mixing and rest time | The oxidation needs time in the mixer and the first rest | Short processes can under-deliver the volume benefit |
Job two: nutritional fortification
| Topic | What to know |
|---|---|
| Why fortify flour | Milling removes the germ and much of the vitamin content; many jurisdictions mandate restoration or fortification of white flour |
| Legal basis | Set by national food law rather than by the baker – check the mandated level and the permitted form before designing the blend |
| Overage | Baking destroys a proportion of the vitamin; the declared label value is the post-bake figure, so the added amount is set higher than the label |
| Losses in baking | Heat, oxygen and extended proofing all reduce the retained vitamin C; heavier, longer-baked products lose more |
| Analytical verification | Test the finished product, not only the flour blend, and agree the method with the customer |
Why the 90% granule suits a mill
A mill or a large bakery blends micro-ingredients into flour at low inclusion rates. At 20-100 ppm, uniformity is the whole game: a patchy distribution means some dough pieces get twice the intended dose and others get none.
| Problem in a dry blend | Why the granule fixes it |
|---|---|
| Segregation during conveying and silo transfer | Granule size is close to that of flour particles and other carriers, so it travels with the blend rather than sifting out |
| Dust in the mill | Low fines content means less airborne vitamin and less housekeeping |
| Feeder bridging | Free-flowing granules feed predictably at low rates |
| Caking in humid stores | Starch-carried granules handle moisture better than fine crystalline powder |
| Blend uniformity at low inclusion | Coarser particles reduce the number of contact points needed to distribute evenly |
The trade-off is dissolution: granules dissolve more slowly and leave a light haze from the starch. In flour and dough this is irrelevant. In a beverage premix it is not, and fine powder is the correct choice there.
Buying and specification notes
| Item | What to fix | Reason |
|---|---|---|
| Grade and assay | 90% granules, assay 89.0-92.0% on dry basis | The dose calculation has to be divided by 0.90, not treated as pure vitamin C |
| Particle size | 90% min through 20 mesh, 25% max through 100 mesh | This is the specification that delivers blend uniformity |
| Starch identity | Which starch is used, and its allergen statement | Needs to be declared on the finished label |
| Microbiology | TPC max 500 cfu/g, yeast and mould max 100 cfu/g, E. coli absent | Starch is a microbial substrate in a food-grade blend |
| Heavy metals | Max 20 ppm | Food compliance gate |
| Regulatory | E300 in the EU; confirm the grade statement your market requires | The permitted form and declaration differ by jurisdiction |