Vegetables - Fresh, Frozen Or Canned
Should all your vegetables be cooked from fresh
? Or when you're busy, can you fall back onto frozen or canned instead?
How fresh is "fresh"?
Frozen
Canned vegetables
A healthy balance of cooked and raw veggies is the key
Fresh vegetables used to be the motto for healthy eating and many health books and cookbooks only ever show fresh vegetables. But busy lifestyles can leave little time for food preparation or growing your own veggies. Unless you can fit in a daily shopping trip, it means that youll have to rely on frozen or canned in place of fresh at least for some things.
Vegetables and fruit are core food groups, important for health and wellbeing. Each day, nutritionists suggest we eat 5 serves of vegetables plus 2 serves of fruit with a variety of different types and different colours (one green, one yellow, one white was what our grandmothers would insist on).
As a group, they are key providers of vitamin C, folate, vitamin K, potassium, magnesium, fibre and a host of antioxidants all for very few kilojoules. So its important to preserve these key nutrients.
And a high vegetable intake is linked to lower rates of cancer, heart disease and blood pressure. Most have a low GI which means they release their carbohydrate more slowly into the body a help with diabetes and weight control.
How fresh is fresh?
Today fresh no longer means just picked. If your fresh vegetables have sat at the markets, then at the greengrocer or the supermarket and then in your fridge before you prepare them, their vitamin levels will have already declined significantly.
If you overcook them or leave them sitting in hot water for more than 5 minutes, that further destroys some (but not all) of the nutrients. Its the heat-sensitive vitamins that are lost vitamin C and two key B vitamins, thiamine (B1) and folate. Minerals (like potassium and magnesium) and fibre are unaffected by cooking.
Given all these factors, frozen vegetables can compare well with fresh ones that have been stored too long or have been over-cooked when it comes to nutrient retention. .
According to a Choice survey in 2007, fresh, raw and canned carrots contained more beta-carotene than other types, but for vitamin C there was little difference between fresh, frozen and canned carrots. Even after cooking, frozen green beans had twice as much vitamin C as cooked fresh beans.
Cooking vegetables makes some nutrients more available to the body for example, beta-carotene and the antioxidant lycopene are absorbed better from cooked carrots or tomatoes. And if you add a splash of olive oil during the cooking, the fat further improves their bio-availability.
Frozen
Frozen vegetables can be as nutritious as home-cooked vegetables provided you cook them quickly in just a little water. Freezing (at -18C for no more than 6 months) is the most nutritious and efficient way to preserve food. Freezing retains more heat-sensitive nutrients (particularly vitamin C, thiamine and folate) and gives a better texture.
Best choices
Firmer-textured vegetables freeze well, such as peas, corn cobs, mixed vegetables, green beans, diced onion and chopped spinach.
Oven-cooked potato wedges or mixed roast vegetables (potato, pumpkin, sweet potato) with less than 8% fat are convenient and compare well with home-cooked.
Pre-sliced stir-fry vegetables in sauce are a good stand-by just check the sodium (salt) content for brands, look for those with less than 600mg per 100g.
Frozen berries, frozen rhubarb.
Remember frozen vegetables are already half cooked due to the initial blanching step, so they need only a quick final heat. Dont overcook.
Canned vegetables
Canning is harsher on the nutrients than freezing. The heat required to sterilise the contents of the can also zaps the heat-sensitive vitamins so canned veggies are not as good a substitute as frozen.
The texture is different too eg canned asparagus taste very different to fresh, canned carrots and potatoes have a softer more-mushy texture. If you only have limited freezer space, a few cans in the cupboard is fine.
Another big drawback is the addition of salt, which can be 5 to 10 times more than whats in fresh vegetables and adds to our already high intake of salt. See the comparison below:
Sodium (salt) in fresh vs. canned:
Vegetable
Fresh or canned
Salt content
Beetroot
Peeled, boiled
51 mg sodium per 100 grams
Beetroot
Canned, drained
279 mg
Tomatoes
Raw
8mg
Tomatoes
Canned, drained
86 mg
Best choices
Select canned tomatoes, beetroots, chick peas, three-bean mix, kidney beans, lentils these are similar nutritionally to what you cook at home and save you time.
Look for canned products with no-added-salt or else drain the liquid away and rinse lightly with fresh tap water to remove as much salt as you can.
A healthy balance of cooked and raw veggies is the key
Eat a combination of both raw and cooked vegetables so that you can take advantage of what both have to offer. A salad at lunch and cooked vegetables at dinner is one way to do this.
Use frozen veggies when youre in a hurry or as a backup when you cant get to the shops. Try to buy fresh items that cant be frozen or canned like cucumber, celery, lettuces, mixed salad packs, fresh herbs (parsley, basil, and dill), baby spinach leaves, mushrooms, broccoli, Asian greens, bean shoots, and avocadoes.
When cooking, the golden rule is to cook until just tender. Dont keep them warm for long periods before you serve them. Use as little water as possible none if you microwave. The best cooking methods are stir-frying, steaming, pressure cooking and in the microwave.
by: Catherine Saxelby
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