Frozen veggies should processed at the peak of ripeness, when their nutrient levels are highest. By doing so, you can preserve an extremely healthy diet through those colder seasons when seasonal product is unavailable.

"While canned vegetables can lose some nutrients during the preservation process (notable exceptions include tomatoes and pumpkin), frozen vegetables may be even more healthful than some of the fresh produce sold in supermarkets, says Gene Lester, Ph.D., national program leader for nutrition, food safety and quality at the USDA. Why is this?Fruits and vegetables chosen for freezing tend to be processed at their peak ripeness, a time when they usually are most nutrient-packed.

While the first step of freezing vegetables—blanching them in hot water or steam to kill bacteria and stop food-degrading enzymes—causes some water-soluble nutrients like vitamin C and the B vitamins to break down or leach out, the subsequent flash-freeze locks the vegetables in a relatively nutrient-rich state. 

Read more at Eating Well