03.Frozen and canned facts
Freezing and canning
- Freezing and canning factories are usually close to where the vegetables are grown. This means that the inevitable loss of nutrients during processing is partly offset by the vegies starting off in a fresher state than you can buy them "fresh" from the supermarket.
- Although canning is definitely not a vitamin C-friendly process, canned vegetables only have to be heated through. So there’s less loss of this nutrient than with fresh or frozen vegetables that take longer to cook.
- On the downside, canned veg often have salt added. It’s not necessary for processing and is best avoided — so check the label and choose brands without added salt.
In contrast, the fresh veg in your local supermarket may not be as fresh as you might think. Advances in technology have made it possible for growers and distributors to keep vegetables looking good for at least a couple of weeks — but they’re not really fresh.
Frozen and canned storage
- Frozen vegies retain most of their nutritional value for up to a year if your freezer is at the right temperature (–18°C) but if it’s not so cold (say –12°C) they lose quality much more rapidly. So check your freezer temperature.
- When you’re buying frozen veg avoid any that are iced together in clumps (they should be free-flowing), as this means they haven’t been handled correctly during distribution.
- It’s also a good idea to take your frozen food home in an Esky or cold bag, and get it into the freezer at home as soon as possible. Treat it as you would ice cream.
- Canned vegetables also gradually lose their vitamins, even when stored under cool conditions; again, they shouldn’t be stored for more than about a year.
- Unfortunately most canned food isn’t required to have a best-before date so the only way to really keep track is to write the date on the can when you buy it — although you still won’t know how long it was sitting on the shelf before that.
Canned greener than frozen
When you use canned vegetables you use less energy and create fewer greenhouse gas emissions than when you use frozen veg.
- It takes more energy to make the can than the plastic or cardboard packaging.
- But frozen foods require more energy for processing and distribution.