Are frozen vegetables as nutritious as fresh ones? Science says yes

As produce prices climb and extreme heat makes storing fresh vegetables difficult, frozen vegetables are emerging as a practical alternative. Contrary to the common belief that freezing depletes nutrients, research shows most nutritional content is preserved.

Demand for frozen vegetables and fruit has been rising. Last year, Lotte Mart's fresh vegetable sales fell 4 percent from the previous year, while frozen vegetable sales grew 10 percent.

Retail tech company Kurly saw frozen vegetable sales rise 23 percent in the first half of this year compared to the same period last year. "Sales have been growing as we added new products such as steaming varieties and greens for seasoned side dishes, beyond the standard vegetable mix," a Kurly official said. The company currently carries 95 frozen vegetable products and plans to expand the lineup to as many as 110 items depending on the season.

"Shoppers in their 30s and 40s tend to buy frozen vegetables because they can use a wide variety without generating food waste, while customers in their 50s and 60s are drawn to frozen staples like green onions and garlic as a more economical option," the official said.

The main reasons consumers choose frozen vegetables are their relatively low price, ease of preparation and long shelf life. The assumption that they are less nutritious, however, does not hold up.

Research shows that fresh vegetables and fruit lose some nutrients after harvest as they are exposed to light, oxygen and heat. Frozen produce, by contrast, is flash-frozen immediately after harvest, which can limit the nutrient loss that occurs during distribution.

One widely cited study is a 2015 experiment by the University of California published in the Journal of Agricultural and Food Chemistry. Researchers analyzed the levels of four nutrients across eight items: corn, carrots, broccoli, spinach, peas, green beans, strawberries and blueberries.

Ascorbic acid levels showed no significant difference in five of the eight items, and in the remaining three, frozen products actually tested higher than fresh ones. Alpha-tocopherol levels were also higher in frozen products for three items. Riboflavin levels showed little difference overall. Beta-carotene was lower in frozen products for only three items. "Overall, the nutrient content of frozen produce was comparable to, and in some cases higher than, that of fresh produce," the researchers concluded.

Vitamin C — particularly vulnerable to environmental exposure — is one nutrient that freezing helps preserve. A study by the University of Georgia, published in the Journal of the Science of Food and Agriculture in 2014, found that frozen broccoli, strawberries and peas contained more vitamin C than fresh counterparts refrigerated for five days.

When cooking frozen vegetables, follow the preparation instructions on the package. Products such as frozen broccoli that have been blanched before freezing can be used immediately after thawing or with brief heating. Vegetables frozen without blanching, however, should be fully cooked before eating.

Once thawed, frozen vegetables should not be left at room temperature for long, as bacteria multiply rapidly. Refreezing thawed products is particularly risky — it not only degrades quality but also raises the risk of food poisoning.