There's a big difference between wholemeal and refined flour. Researchers share their best tips to help you avoid unpleasant surprises.
"Wholemeal flour starts to smell rancid after about two years," says researcher Shiori Koga. She and colleague Simon Ballance study grains and health at Nofima.(Photo: Anders Moen Kaste)
Yes – grains go rancid even when stored dry, according to researchers Simon Ballance and Shiori Koga at the food research institute Nofima.
Oats are especially vulnerable because of their high fat content. That's why they are heat-treated before being packaged and sent to stores, whether they are cooked or uncooked oats or oat flour.
This heat treatment deactivates the enzymes that lead to rapid rancidity of the fat in oats.
Oats come with a best-before date, Ballance explains, but they usually last much longer if stored properly.
Can last well beyond the date
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"Keep oats in a dark, dry kitchen cupboard. That usually works well," Ballance says.
The best-before date and storage advice apply to all types of flour and grains.
Reaching the best-before date doesn’t automatically mean the product has gone bad.
Still, shelf life varies greatly depending on the type of grain and how finely it's milled, Koga notes.
It's comes down to fat
"Wholemeal flour starts to smell rancid after about two years. I've seen that in my samples," says Koga.
Wholemeal flour is different from refined wheat flour.
"Refined flour contains very little fat. Wholemeal flour contains the outer part of the grain, which has the most fat," says Koga.
The same principle applies to oats. Koga says that oats contain about five to six per cent fat, while wheat contains about two per cent.
"And if you're not careful, you might get insects," Ballance warns.
Occasionally people discover beetles and larvae in their flour. To prevent this, store the flour in sealed packaging in your kitchen cupboard.
The hull protects against rancidity
Grains are processed into different products. For oats, the outer hull has to be removed, otherwise the grains become too hard to eat.
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That hull also protects against rancidity. Once it's removed, things start happening.
"This process happens much more slowly when the grain is whole. But when oats are ground into flour, the surface area becomes much larger, which speeds things up – even though the oats have been heat-treated after dehulling," says Ballance.
According to the researchers, it only becomes truly dangerous if moisture gets in and mould starts to grow. That's why storing it in a dark, dry cupboard is key.
If you do that, you can safely rely on the look-smell-taste method.
