Fresh is best – right? In fact, studies on the relative benefits of fresh and frozen show no consistent differences
The Guardian-Peas … no big difference nutritionally between fresh and frozen. Photograph: Alamy
When you are shopping for juicy strawberries or fresh greens, you may not stop at the frozen food aisle. Frozen fruit and vegetables often don’t look the part once defrosted, and you may think that the freezing process depletes them of some nutritious value. Nothing is as good for you as fresh – right? On the other hand, frozen is often cheaper and is there all year round. And fresh is a relative term; fruit and vegetables can be in transit, sit in stores or wait in your fridge for some weeks. But can you get the same nutritional benefit from your frozen five a day?
Many had a go at perfecting the freezing process before Clarence Birdseye (the captain himself) came up with “quick-frozen” technology in the early 1920s. He copied Inuits in Alaska, who preserved their fish by freezing them quickly, meaning that large ice crystals didn’t form to damage cells and destroy the taste of the food. Fruit and vegetables are between 70% and 90% water, and, once harvested, rapidly lose moisture, are attacked by microbes and degraded by enzymes.
Nowadays, newer techniques are used, such as blanching vegetables before flash freezing. There are no chemicals involved, and, if you worry about frozen fruit and vegetables losing nutrients, then remember that fresh ones lose them too. Green peas lose just over half their vitamin C in the first 24 to 48 hours after picking. A study by Ali Bouzari and colleagues at the University of California, comparing nutrients in eight different fresh and frozen fruit and vegetables (corn, broccoli, spinach, carrots, peas, green beans, strawberries and blueberries), found no consistent differences between fresh and frozen.
Vitamin C was higher in frozen corn, green beans and blueberries than in their fresh equivalents. There was more riboflavin (a B vitamin) in frozen rather than fresh broccoli, though fresh peas had more than frozen ones.
In another paper, the researchers looked at fibre and levels of minerals such as magnesium, calcium, zinc and iron and found no big difference between the frozen and fresh forms of the same eight fruit and vegetables.
Fans of frozen fruit and vegetables (and there are many in the food industry) argue that freezing stops the rotting process in its tracks. Frozen fruit and vegetables, if kept undisturbed in a good freezer, will have been captured and preserved in their prime and retain their minerals and vitamins. Issues such as preferring the taste of fresh are more subjective. And, of course, frozen peas are much better than fresh ones for applying to minor bumps on the head.