Vitamin C: Usually lost in higher concentrations than any other vitamin. A study was conducted on peas to determine the cause of vitamin C loss. 10% of the vitamin loss occurs during the blanching phase, and the rest occurs during the cooling and washing phases. Vitamin loss is not actually recognized as a freezing process. Another experiment involved peas and lima beans. Frozen and canned vegetables were used in the experiments. Frozen vegetables are stored at -23°C (-10°F) and canned vegetables are stored at room temperature 24°C (75°F). Vegetables were analysed with and without cooking after 0, 3, 6 and 12 months of storage. O'Hara, the scientist who conducted the experiment, said: "In terms of the vitamin content of the two vegetables at the time of consumption, there does not appear to be any clear advantage to the preservation method, frozen storage, canning or glass processing."
Vitamin B1 (thiamine): 25% loss of the vitamin is normal. Thiamine is easily soluble in water and destroyed by heat.
Vitamin B2 (riboflavin): Not much research has been done to determine how freezing affects riboflavin levels. Studies that have been conducted are inconclusive. One study found an 18 percent loss of vitamins in green vegetables, while another found a 4 percent loss. It is widely believed that the loss of riboflavin is related to the freezing preparation rather than the freezing process itself.
Vitamin A (carotene): Little to no carotene is lost during the preparation and freezing of most vegetables. Most vitamin loss occurs during prolonged storage.
