How nutritious are commercially-frozen vegetables compared to fresh vegetables?

This answer is brought to you by many of the Australian nutrition professionals who regularly contribute to a nutrition email discussion group.

Freezing is a very efficient method of preserving the nutritional value, texture and flavour of many vegetables. Most vitamins will keep well in frozen vegetables. Carotene (a compound that is converted to vitamin A in the body) may actually be better preserved in frozen produce because packaging keeps the vegetables away from light (which destroys carotene).

For example, frozen peas typically have about 60% more carotene than 'fresh' peas (that have been exposed to light during their trip to the market and while awaiting sale).

Some losses of vitamin C and folate (also known as folic acid) occur during commercial freezing. About 25% of the vitamin C, and perhaps a greater percentage of the folate, will be lost during the blanching process that precedes commercial freezing. A smaller quantity (perhaps 10%) of the thiamin (formerly called vitamin B1) will be lost during blanching. Little further loss occurs during the time the food is kept frozen, provided that it has been stored properly (-18 degrees C for no more than six months).

However, the vitamin losses associated with blanching and the thawing/cooking process are similar to those that occur during normal cooking of fresh vegetables. This means that, provided they have been stored and then cooked properly, frozen vegetables provide similar levels of nutrition to fresh vegetables. It is also worth noting that for cooking both frozen and fresh vegetables, microwave cooking and steaming are both superior (in terms of retaining nutritional value) than boiling in a large volume of water.

Other vitamins are generally fairly heat stable and are largely retained during the blanching process and subsequent period of frozen storage, or are not found in significant quantities in vegetables anyway. Nutrients other than vitamins are not significantly affected by the freezing process.

In Australia it is recommended that people eat seven serves of fruits and vegetables each day, with five of these being vegetables. Some people find it inconvenient to prepare fresh vegetables. This can lead to a reduction in their intake of vegetables generally. Therefore, frozen vegetables (which are already washed, peeled and sliced or diced) can be a useful way of encouraging greater intake of these highly nutritious foods. To retain the maximum nutritional value, texture and flavour of frozen vegetables (and of most other frozen foods) the following is recommended by the CSIRO Division of Food Research:

Collect your frozen foods last at the supermarket and take them home in insulated containers.

Put frozen food in a freezer maintained at about -18 degrees C as soon as you arrive home.

Frozen storage for no more than about six months is recommended for most vegetables.

Steam or microwave frozen (and fresh) vegetables to retain a high proportion of the vitamins.

If cooking frozen food in boiling water, the food should be taken directly from the freezer and placed in water that has already come to the boil.

Boil vigorously until ready, and then serve immediately (ie, do not leave the food 'simmering' for long periods).

Do not use saucepans or other utensils made from copper or brass.

Cooking utensils made from glass, stainless steel, aluminium or enamel do not affect the nutritional content.

Issued 1999

*Statements and opinions presented in the Frequently Asked Questions do not necessarily reflect the policies or opinions of Nutrition Australia, nor does Nutrition Australia accept responsibility for the accuracy of such statement and opinion.

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Disclaimer: This material is provided on the basis that it constitutes advice of a general nature only. It is not intended to replace the advice of a physician or a dietitian.