Can a Price Sticker Identify GMO Tomatoes? What PLU Codes Really Mean

No, the sticker on a tomato cannot tell you whether it is genetically modified. A widely shared tip says that a five-digit price code beginning with 8 marks a GMO, 9 means organic and four digits means conventional. Only part of that is true. The “9” prefix for organic produce is real, but the “8” prefix was never used for GM produce in shops, and the code system was never designed to inform shoppers about genetics. In practice, almost every tomato you can buy is not genetically modified anyway.

Here is how the codes really work, which GM tomatoes have actually existed, and which labels you can rely on if you want to avoid GM food.

How PLU codes really work

Price look-up (PLU) codes are the small numbers on stickers attached to loose fruit and vegetables. They are managed by the International Federation for Produce Standards (IFPS), a global group of fresh-produce associations, and their job is simple: help cashiers ring up the right item and help shops track stock.

Four digits, usually in the 3000 or 4000 range, identify an ordinary, conventionally grown item and often its size or variety. Bananas, for example, are 4011.
Five digits starting with 9 mean the organic version of the same item, so organic bananas are 94011.
Five digits starting with 8 were set aside years ago as a possible marker for GM produce. Growers and retailers never adopted it, and the IFPS has been opening the 83000–84999 block up for ordinary produce codes instead.

Using the codes is largely voluntary for shops, and a missing sticker or a missing 9 tells you nothing definite either. Hong Kong’s Centre for Food Safety put it plainly in 2022: PLU codes are not a way to identify GM food, and only laboratory testing can confirm whether produce is genetically modified.

Are GM tomatoes actually sold?

Very few GM tomatoes have ever reached shoppers. The first was the Flavr Savr, developed by the Californian company Calgene to soften more slowly after picking. The US Food and Drug Administration cleared it in 1994, finding it as safe as conventionally bred tomatoes. It was expensive to produce, bruised easily in machine harvesting and never made money, and it disappeared from shelves within a few years.

Two newer examples exist. In 2021 Japan began selling a gene-edited tomato with around five times the usual level of GABA, a compound marketed for relaxation and blood pressure. In 2022 the US Department of Agriculture cleared a purple tomato developed at the John Innes Centre in Norwich, England, using genes from snapdragon flowers to boost anthocyanin pigments, the same family of antioxidants found in blueberries. It went on limited sale in the US in 2024, mainly as seeds for home gardeners and in small quantities.

So the red supermarket tomato in Europe, and almost certainly in the US, is a conventionally bred variety. Its features come from ordinary plant breeding, growing conditions and ripeness.

Can you tell by cutting a tomato open?

Social media posts like the one in the picture above claim you can spot a GMO tomato by the pattern of seeds and pale flesh inside. That does not work. The size of the core, the amount of white tissue and the shape of the seed cavities depend on the variety, how ripe the fruit was when picked, and how it was stored. Many commercial tomatoes are picked firm and ripened in transit, which can leave pale, tough centres. That says something about flavour, not genetics.

If you care about taste, look for tomatoes sold ripe on the vine, buy in season, or try local and heirloom varieties. And keep them out of the fridge if you plan to eat them within a few days; cold dulls their flavour.

Labels you can actually rely on

If you prefer to avoid GM ingredients, packaging rules give you better tools than a price sticker:

Organic certification. Certified organic food in the EU and the US must be produced without genetically modified organisms, so an organic logo is a reliable shortcut.
EU labelling. In the European Union, food containing more than 0.9% of GM material must say so on the label, including processed foods and animal feed.
US “bioengineered” disclosure. Under a law passed in 2016, the US Department of Agriculture created a national standard requiring manufacturers, importers and some retailers to disclose bioengineered foods by text, a symbol or a digital link. Compliance became mandatory in 2022.
Voluntary non-GMO seals. Independent schemes certify products as non-GMO; they are useful but private standards, so read what they cover.

In the US the GM ingredients people meet most often are not fresh vegetables but products made from corn, soybeans, sugar beet and cotton. By 2015 about 92% of US corn and 94% of soybeans were GM varieties, which is why oils, syrups and starches in processed foods are the usual source.

What science says about GM food safety

The old version of this story said GM food had been linked to damage in “virtually every organ” and that most developed nations considered it unsafe. Neither claim holds up. Major scientific bodies, including the US National Academies of Sciences in a large 2016 report, have concluded that the GM foods currently on the market are no riskier to eat than their conventional counterparts. The same bodies stress that each new GM product should be assessed individually, which is what regulators do.

That does not end every debate. People object to GM crops for many reasons that are not about food safety: corporate control of seeds, herbicide use on herbicide-tolerant crops, effects on small farmers, and simple consumer choice. Those are legitimate questions, and clear labelling helps people act on their own views.

What Europe banned, and what it didn’t

It is often said that Greece, Austria, France, Germany, Hungary and Luxembourg “ban GMOs”. The accurate picture is narrower. A 2015 EU directive allowed member states to opt out of growing GM crops on their territory. Under a Commission decision of 3 March 2016, cultivation of the insect-resistant maize MON 810 was barred in 19 member states, including those six countries, and in parts of Belgium and the United Kingdom.

Those decisions cover farming only. GM products that pass the EU’s approval process, mostly imported soy and maize for animal feed, can still be sold, and they must be labelled when used in food. Greece remains one of the countries that does not allow GM crops to be grown on its farmland.

Sources: Wikipedia: Price look-up code; Centre for Food Safety, Hong Kong (2022): Can we identify GM foods from PLU codes?; Wikipedia: Flavr Savr; Wikipedia: Genetically modified food; USDA: National Bioengineered Food Disclosure Standard; EUR-Lex: Commission Implementing Decision (EU) 2016/321. The original tip circulated via Why Don’t You Try This.

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