Citric acid is the most-feared harmless ingredient in the supermarket. It appears near the top of “additives to avoid” lists, it gets flagged by apps that count E numbers, and it is in a lemon.
It is worth spending a page on precisely because it is boring. If your method for spotting ultra-processed food flags citric acid, the method is wrong — and most methods do.
What it is and what it does
Citric acid is a weak organic acid, and the reason citrus fruit tastes sharp. It is also a step in the citric acid cycle, the reaction sequence your cells use to release energy from food. You are producing and consuming it constantly regardless of what is on any label.
As E330 it does several unglamorous jobs:
- Controls pH— keeping a product in the acidity range where it is stable and safe.
- Preserves— a lower pH makes life harder for spoilage bacteria.
- Protects colour and flavour— it binds trace metals that would otherwise catalyse browning and rancidity.
- Adds sourness— the one arguably cosmetic use, in sweets and soft drinks.
Is it natural?
The molecule is identical to the one in fruit. The production route is not: commercial citric acid is made by fermenting a sugar source with the mould Aspergillus niger, which is enormously cheaper than extracting it from citrus.
Whether that makes it “natural” is a question about language rather than chemistry. The fermentation is an industrial process; the substance it produces is the one in your orange juice. This is a good example of why “natural” is close to useless as a food label — and why NOVA deliberately asks what a substance is for rather than where it came from.
Why citric acid is not a UPF marker
This is the part that matters. Under the NOVA classification, a food is group 4 when it carries markers of industrial formulation — cosmetic additives such as colours, flavourings, flavour enhancers and non-sugar sweeteners, or ingredients like protein isolates and modified starches that never appear in a home kitchen.
Acidity regulators are not on that list. Neither are preservatives or antioxidants. NOVA group 3 — processed foods — is explicitly the home of tinned vegetables, tinned fish, cured meats and preserved fruit: foods made durable by exactly the kind of additive citric acid is. Preservation is the oldest reason humans processed food at all, and NOVA does not treat it as a fault.
So a tin of chopped tomatoes listing tomatoes, tomato juice and citric acid is not ultra-processed. An app that says otherwise has confused “contains an additive” with “contains a marker of ultra-processing”, which are different claims. Our additives guide sets out which classes are markers and which are not.
The one real caveat
Frequent consumption of very acidic drinks can contribute to dental enamel erosion, and citric acid is part of what makes them acidic. That is a reason to think about how often you drink acidic soft drinks — it is not a reason to avoid tinned tomatoes. The dose and the context are the whole argument, and stripping them out is how a reasonable caution becomes an internet scare.
What to take from this
Counting additives is not a method. It rewards products that hide formulation behind vague terms and punishes honest tins of vegetables. Read what each additive is for: a preservative or acidity regulator is doing a job humans have wanted done for centuries, while a flavouring or a colour is there to make a formulation pass for food. Cull names every additive and says which kind it is, rather than handing you a count and letting you assume the worst.