Aflatoxin in dry fruits: what it is, how it is tested

Of everything a lab tests in a pack of nuts, one line deserves your attention above all the others: aflatoxins. Invisible, tasteless, heat-stable and genuinely dangerous over time, they are the reason “who stored this, and how” matters more than any superfood claim on the front of a pack. This is what they are, where the risk actually lives, and how testing protects you.

What aflatoxins are

Aflatoxins are toxins produced by common moulds — chiefly Aspergillus flavus and A. parasiticus — when they grow on crops stored warm and damp. Of the family, aflatoxin B1 is the most potent: it is classified as a Group 1 human carcinogen (liver) by IARC, and chronic low-dose exposure is the concern, not one unlucky snack. You cannot see, smell or taste contamination, and normal cooking does not destroy it. Detection is a laboratory job, full stop.

Where the risk concentrates

Aflatoxin risk is a storage story. The mould needs moisture and warmth, so the danger zone is the gap between harvest and airtight packing — crops dried slowly in humid weather, warehouses without moisture control, jute sacks through a monsoon. Groundnuts, maize, chillies and tree nuts are the classic high-risk crops. Among dry fruits, anything sold loose from open bins deserves more scepticism than sealed, batch-coded packs, whatever the bin’s pedigree.

Makhana starts with a structural advantage — the kernel spends its life sealed inside a hard shell underwater — but the advantage is squandered if popped makhana then sits absorbing humidity in an open warehouse for months. Speed and dryness after popping are the whole game, which is why popped makhana should be packed quickly and kept dry.

The limits, and what a good result looks like

FSSAI’s Contaminants, Toxins and Residues Regulations (reg 2.2.1, as of October 2026) cap total aflatoxins in nuts at 15 µg/kg (parts per billion), with a stricter 10 µg/kg for B1; many export markets set lower bars still. Makhana has no row of its own in that table, so the nut limits are the nearest reference. On a lab report you want the aflatoxin line to read “not detected” or “BLQ” (below the limit of quantification) — or a number that is a small fraction of the cap. A result at, say, 2 µg/kg against a 15 µg/kg limit is a pass with room to spare, not a warning. If you want to get fluent in reading the whole document, we wrote a field guide.

What you can do as a buyer

Buy sealed and batch-coded, not loose. Ask for the report for your batch — an annual certificate says little about the pack in your hand. MiamiNuts test reports are available by email on request; quote the batch code from your pack. Store dry at home: airtight, away from the stove’s steam; refrigerate long-holding nuts in humid months. Discard the suspicious: any mustiness, visible mould or damp clumping is a bin decision, not a taste test.

Aflatoxin is the strongest argument for the boring virtues — fast supply chains, dry storage, per-batch testing. None of them photograph well.

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