How do antioxidant vitamins hold up when frozen?
Meat & Poultry: There is little difference in nutrition during frozen storage.
Green Veggies: Fresh and frozen samples of peas, green beans, broccoli, and spinach were tested. Vitamin C content didn't differ much between fresh and frozen samples except for frozen green beans, which were found to have significantly higher levels compared to their fresh counterparts. Riboflavin (Vitamin B) levels remained consistent in fresh and frozen samples, except for frozen peas, which lost some riboflavin during storage. Alpha-tocopherol (Vitamin E) levels were much higher in frozen peas and green beans compared to fresh; frozen spinach also showed higher levels. The higher level in some foods may be due to the steam blanching process, increasing alpha-tocopherol's availability. More than 50% of initial beta-carotene (Vitamin A) content was lost during frozen storage of peas and spinach; fresh peas lost at least 15%.
Other Veggies: Fresh and frozen samples of corn and carrots were tested. Vitamin C content was not significantly different between fresh and frozen carrots; however, frozen corn had significantly higher levels than fresh. Alpha-tocopherol was decreased in fresh corn and carrots, while frozen corn had higher levels. The higher level may be due to the steam blanching process, increasing alpha-tocopherol's availability. More than 50% of beta-carotene was lost during frozen storage for carrots, at least 15% was lost during fresh storage.
Fruits: Fresh and frozen samples of strawberries and blueberries were tested. Vitamin C content did not vary significantly between fresh and frozen strawberries, while frozen blueberries had significantly higher levels compared to fresh. Riboflavin levels remained consistent in fresh and frozen samples. Alpha-tocopherol was higher in frozen blueberries.
The Buddy-System Phenomenon: When fresh broccoli is chopped or chewed, glucoraphanin and an enzyme called myrosinase team up to create sulforaphane - a cancer-preventing compound. When broccoli is blanched before freezing, the heat destroys myrosinase so the cancer-preventing compound cannot be created. Researchers decided to try to fix this problem by adding more myrosinase to the frozen broccoli. They sprinkled a small amount of daikon radish (another cruciferous vegetable) to the broccoli and found the two worked together to create sulforaphane, restoring the cancer-preventing properties of the frozen broccoli. To get this benefit at home, sprinkle your frozen broccoli with other cruciferous vegetables like raw radish, cabbage, arugula, or spicy mustard before cooking. (3, 4)