Like many people, I'm tightening my belt when it comes to my food budget. I am wondering whether there is much nutritional goodness in canned foods, or if frozen vegetables are perhaps a better option?

Canned foods may contain a lot of goodness, although some are more nutritious than others. Things such as canned steak and kidney pies and steamed puddings are as high in fat and sugars as fresh versions and not one of the best healthy options. But canned fruits, vegetables, fish and meat can represent good value for money and nutrients.

From a processing point of view, the can and its contents are usually exposed to hot water or steam that heats the food inside to 95C. Lids are then sealed and the can is sterilised to around 121C for several minutes to kill bacteria and the cans are then cooled.

Because of this heat treatment, sensitive nutrients such as vitamin C are reduced through canning. While a 100g of fresh oranges (a medium-sized orange) has 54mg of vitamin C, a 100g serving of canned mandarin oranges has 20mg. While obviously less, this is still half of your day's requirement.

In some cases the canning process has advantages. For example, the orange and red antioxidant pigments, such as betacarotene in carrots and lycopene in tomatoes, are easier for your body to absorb after heating - making canned versions of carrots and tomatoes a better source than fresh versions eaten raw.

Needless to say, opting for vegetables canned in water rather than salted water, and fruit in natural juices rather than syrup, is a good move nutritionally. Vegetables canned in brine tend to give you around 1g of salt per 100g serving compared with none in the fresh version, while fruit canned in syrup gives you about 14g of sugar per 100g serving compared with 9.7g when canned in juice.

Minerals such as iron and calcium as well as protein are not affected much by canning. This means that foods such as canned sardines and canned meats are still really nutritious. In fact, canning helps to soften the bones in fish such as sardines and anchovies. This makes the bones edible and a great source of bone-building calcium. A 100g serving of canned sardines eaten with their bones gives you 500mg of the 700mg of calcium that both men and women need daily.

Omega-3 oils also survive the canning process, which makes canned fish such as mackerel and sardines an excellent source of these essential fats. Having them on toast (mashed with some lemon juice and black pepper) makes a really nutritious, good-value-for-money and easy-to-make supper.

When it comes to the specific benefit of frozen vegetables over canned, again it depends on which ones you are talking about. Good quality brands of frozen vegetables are blast-frozen within a couple of hours of harvesting, which stops losses of vitamin C and B vitamins in their tracks. If you store and cook them according to pack instructions then frozen vegetables such as garden peas are likely to have more vitamin C than their fresh counterparts and certainly more than canned ones.

For vegetables such as carrots and sweetcorn, it does not make much difference because their main nutritional benefits come from the colourful pigments.

Keeping it safe

Unlike other oily fish, canned tuna is not a good source of omega-3. This is because tuna is cooked before it is canned and most of its oils are lost during this process.

Avoid any badly dented, blown or rusty cans. The contents could have spoiled and cause serious food poisoning.

Quick freezing methods form small ice crystals in the food which helps to reduce damage to the texture and flavour of the food.

Keep a temperature probe in your freezer and ensure that it remains minus 18C or colder to preserve nutrients and texture. Try to use within three months of purchase.

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