Contrary to the common belief that fresh fruits and vegetables are always better, some foods retain nutrients more effectively when frozen, and certain compounds can even be present in higher amounts.
According to the medical community Thursday, Dr. Karan Rajan, a surgeon with Britain's National Health Service (NHS), named blueberries, spinach, and peas as foods whose nutritional benefits are especially pronounced when frozen. The reason is that most frozen produce is frozen within 24 hours of harvest, potentially giving it a nutritional edge over fresh products that sit on store shelves for several days.
For blueberries, the freezing process slows the rate of nutrient loss, preserving vitamin C and polyphenols longer. When researchers at South Dakota State University in the United States measured anthocyanin content by freezing period, fresh blueberries averaged just 3.32 milligrams per gram, but blueberries frozen for 133 days rose to 8.89 milligrams. The analysis suggests this is because ice crystals formed during freezing break down cell tissue, allowing anthocyanin, a water-soluble pigment, to be released more easily.
Spinach, when blanched and frozen, can reduce the loss of vitamin C and antioxidant compounds that drop sharply immediately after harvest. Dr. Rajan explained that a significant portion of the iron in fresh spinach is difficult to absorb, but blanched and frozen spinach contains less oxalic acid and other substances that hinder absorption, improving iron availability. Peas also lose vitamins as time passes after harvest, but flash freezing can slow the loss. He added that frozen peas contain higher levels of B vitamins, which are involved in energy metabolism and nervous system function, and vitamin E, which protects cells from free radicals, than fresh ones.
Another study comparing corn, carrots, broccoli, and strawberries in fresh and frozen states also found that the vitamin content of frozen products was similar to or sometimes higher than that of fresh products. However, experts stress that this does not mean fresh foods are inferior to frozen ones, but simply that their nutritional composition is different.
