May 30, 2014

Fresh vs. Frozen

In two recent studies from Britain, researchers purchased a half dozen different kinds of fruit and vegetables, all of which came in two varieties: fresh and frozen. After buying them and then having them chill out in either a fridge or freezer for three days, researchers conducted 40 tests to compare their nutritional content.

Turns out the frozen varieties were richer in health-boosting vitamins and antioxidants. In fact, frozen broccoli had four times more beta-carotene than its fresh counterpart, while frozen carrots had three times more lutein and double the beta-carotene as well as greater levels of vitamin C and polyphenols. Raspberries and peas performed about the same, whether they were fresh or frozen.

While it is true that foods gradually lose nutrients as they move through the supply chain, that chain is far longer for fresh produce. Fruits and vegetables are regularly held in storage for up to a month before you ever see them. Plus, according to study author Graham Bonwick Ph.D., a professor of applied biology at the University of Chester, once they hit your refrigerator  the nutritional loss escalates. It is probably due to the plant's continuing metabolic activity and how cells react to oxygen and exposure to artificial dark-light cycles.

A recent study from Rice University and the University of California at Davis found that the fluorescent lights of supermarkets and the constant darkness of your refrigerator affects fruit and vegetable circadian clocks so that they excrete fewer glucosinolates, compounds with cancer-fighting properties.

"Produce's degradation reactions are very much slowed by lowering the temperature to freezing levels," Bonwick says. "Furthermore, when you freeze produce, the water present in the cells of the food is locked up as ice, slowing or preventing these processes that require the presence of free water." Since produce in the freezer section was frozen solid almost immediately after being picked, it is preserved at its nutritional peak.

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