Poorly stored nuts on supermarket shelves

Rancid nuts in supermarkets: the expiry date scam

Bags of walnuts and almonds show expiry dates years away, but when you open them the taste is rancid. This is not an isolated case: dozens of consumers report the same problem across different brands. The cause is not time, but deterioration caused by increasingly low-quality packaging and, according to some analyses, fraudulent repackaging practices.

Packaging that doesn't preserve
Manufacturers have cut costs on packaging: functional zip closures have given way to micro-zips that don't reseal after the first opening, and thick materials have been replaced with ultra-thin plastics that don't seal properly. The result is that the vacuum is lost and the nuts oxidise and go rancid, even when the printed date is correct. This pattern repeats at Lidl, Aldi and other chains, especially in the ultra-thin plastic tubs.

Who makes what we buy?
Packaged nut production is concentrated in a few groups: Borges, Medina and, to a lesser extent, Frumesa. Most own-brand products from different chains come from these same manufacturers, which explains why the problem is so widespread. Only some products, such as Mercadona's zip-free sealed bags, seem to stay fresh thanks to a more airtight seal.

The risk of aflatoxins
Poor-quality peanuts can contain aflatoxins, toxins produced by the Aspergillus fungus. The European Food Safety Authority (EFSA) warns that these substances are carcinogenic and are associated with a higher risk of liver cancer. Peanuts imported from China are particularly flagged for their weaker quality control, although those from the US are also considered acceptable. However, rancidity from oxidation is not always accompanied by fungus, but the lack of guarantees in storage increases the likelihood of contamination.

Repackaging: the hidden business
Some distributors return unsold nuts to shady companies, which repackage them with new expiry dates and reintroduce them to the market. This practice, reported on consumer forums, would affect major chains such as Carrefour, Alcampo or Mercadona. This way, a product that has been oxidising for months can end up on the shelf looking fresh.

The question that remains: to what extent do the quality controls of the big chains allow altered products to reach the shelves? Meanwhile, consumers can only trust their nose and choose in-shell nuts sold in bulk, which offer a better guarantee of preservation.

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