Wednesday, December 4, 2013

When Frozen Beats Fresh

A University of Georgia study of Americans' groceries has discovered that fresh isn't always best — at least not in terms of delivering vitamins and minerals. Led by Ronald Pegg, associate professor of food science and technology, researchers studied the vitamin and mineral content of eight fruits and vegetables — blueberries, strawberries, broccoli, green beans, corn, spinach, cauliflower and green peas. They analyzed the nutrient values of the produce on the day they were purchased and after the produce had been stored in a household refrigerator for five days. They also analyzed the nutritional content of the same set of fruits and vegetables that had been packaged after freezing.

"The vitamins and nutrients in fruits and vegetables degrade over time, and we found that frozen fruits and vegetables may offer more nutrition than fresh, when storage is taken into account," Pegg said. "(Fruits and vegetables) are going to have a different nutrient profile after storage than they had when they were taken from the field ... (These pieces of produce) are living things. They respire; they age and they break down over time. There are oxidative stresses, microbial stresses and enzymatic stresses, and we end up seeing the loss of nutrient value from these stresses."

Pegg's study showed that some frozen fruits and vegetables had higher levels of vitamin A, vitamin C and of folates than fruits and vegetables that had been stored for five days.

Shoppers tend to consume some of their produce on the day the purchase it from the grocery store and store the rest in the refrigerator for later use. The researchers looked at nutrient levels of the fruits and vegetables after storage to get a better picture of the nutrition that American shoppers are getting from their produce.

"This particular study was designed from the point of view of the consumer, and it's one of the first to take into account the way people buy and store produce," Pegg said.

Since many shoppers only buy produce on a weekly or biweekly basis, frozen produce may be a more effective way to get the nutrients and vitamins available in fruits and vegetables.

"Freezing is nature's pause button. It helps maintain the nutritional value of fresh vegetables, even during storage."

Frozen vegetables are able to maintain more of their nutritional value because they are blanched shortly after being taken from farmers' fields. This stops the enzymatic reactions that can break down many nutrients. Freezing also slows the enzymatic breakdown of fruits, which are not blanched, and decreases microbial break down.

Sources: Ronald Pegg
UGA College of Agricultural and Environmental Sciences

Artwork: 4 Basic Food Groups Poster