Vitamin C losses in some frozen vegetables due to various cooking methods

Frozen spinach, peas, green beans and okra were commercially cooked in three different stewpans (double based stainless steel, teflon, pyrex) with and without thawing. The vitamin C levels were effected both by cooking methods and stewpans. Frozen peas were found to be the least (3.5% loss), and frozen green beans were found to be the most (19.6% loss) effected vegetables by thawing. In all of the stewpans, double based stainless steel pan retained more vitamin C than the others. While boiling spinach, peas, green beans, and okra without thawing resulted 46.5, 25.2, 18.2, and 21.6% vitamin C loss in double based stainless steel pan, boiling them in pyrex pan resulted 58.5, 36.0, 42.1, and 28.2% vitamin C loss, respectively. Besides, the losses in cooking processes were accelerated in thawed vegetables with the same tendency; that is more destruction occurred in samples boiled in pyrex pan (60.3% loss in spinach, 40.8% loss in peas, 48.4% loss in green beans, and 41.6% loss in okra). According to the results, it was found that thawing before cooking is useless and causes more vitamin C loss. Therefore, frozen vegetables must not be thawed before cooking. In order to prevent vitamin C from destruction, using double based stainless steel pan, minimum amount of water and cooking of frozen vegetables are recommended.