Sales of canned and frozen foods have been rising sharply lately as people try to stock up on food that will last a long time without expiring, and even freezer sales have increased.
But many people believe that vegetables and fruits are best eaten fresh and have the most nutritional value, so eating canned fruits and vegetables or frozen fruits and vegetables is harmful to our health?
Fatima Hachem, a senior nutrition officer at the United Nations Food and Agriculture Organization (UN FAO), said that food has the highest nutritional value when it is harvested, and that fresh crops begin to lose nutrients as soon as they are harvested, because once they leave the soil or branches, they lose their source of nutrients and energy.
“Vegetables used for fresh cooking may lose some of their nutritional value if they are left for a long time.”
Some nutrients are particularly easy to lose, such as vitamin C, which helps the body absorb iron, reduce cholesterol and fight free radicals, if they are exposed to air and light.
Chilling fresh fruits and vegetables in the refrigerator can slow down the rate of nutrient loss, but each vegetable and fruit loses its nutritional value at a different rate.
There have been many studies on the nutritional value of fresh, frozen and canned fruits and vegetables. If stored in the refrigerator for 7 days at room temperature, it lost 100% of its vitamin C. If stored in the refrigerator, it lost 75% of its vitamin C. But carrots lost only 27% of their vitamin C after 7 days at the same room temperature.
Compared to carrots, spinach is tender and thin, easily losing water and oxidizing, and less heat-resistant, Barrett said.
Quick freezing
For example, spinach loses only 30 percent of its vitamin C when it is frozen because freezing suspends the oxidation process, which is one of the reasons why fruits and vegetables gradually turn yellow after they are picked.
The industrialization of agriculture has enabled large-scale freezing. Taking the most common peas as an example, industrialized technology can now complete the process of picking peas, washing them, boiling them, and freezing them rapidly in less than two hours, whereas 50 years ago the whole process took several days.
But after the fresh fruit and vegetables are picked, they have to be sent to a packaging plant to be graded and packed, and then distributed to supermarkets around the world before finally reaching consumers’ homes.
Richard Harrow, chief executive of the British Frozen Food Federation, said that in 99 percent of cases, the process takes longer than fast-freezing.
Canned fruits and vegetables
Food loses less nutrients when it is frozen quickly, but when it is canned, it goes through instantaneous high-temperature sterilization and loses more nutrients.
Like fresh fruits and vegetables, different fruits and vegetables are canned at different rates of nutrient loss.
Barrett found that vegetables and fruits containing water-soluble nutrients such as vitamin C and vitamin B, such as spinach, are more suitable for fresh consumption and less suitable for canning.
Vegetables and fruits containing vitamin A and vitamin E and other fat-soluble nutrients, such as carrots and tomatoes, are better suited for canning.
But Hachem said that although frozen or canned fruits and vegetables do not affect their nutritional value, but frozen is better, because canned usually add salt, or added sugar (canned fruit).
But canning also has its own irreplaceable advantages, especially since canned foods are usually safer and less prone to germs.
Barrett said the advantage of canning food is that it goes through a sterilization process, which loses a lot of nutrients but also eliminates all microorganisms, making it safe to eat once it’s in the can.
Eating a variety of foods
Whether fresh or frozen or canned, the most important thing is to eat a variety of foods, fresh, frozen and canned, says Hachem.
“You can cook with frozen vegetables and canned vegetables, but that’s no substitute for a fresh salad,” he said.
If you’re only buying once a week, make sure the vegetables and fruits are preserved for maximum nutritional value.
If we can have a fresh salad every day with frozen or canned vegetables, there’s no lack of nutrient intake and, on the contrary, it’s consistent with multiple nutritional requirements.
Fresh fruit and salads may not be readily available to everyone, especially at this time of year, but experts say that doesn’t mean we can’t get enough nutrients.
Whether it’s frozen, canned or fresh, the most important thing is to always eat your vegetables and fruits, no matter how they are preserved.
The NHS in the UK recommends five servings of vegetables and fruit per person per day, whether frozen, canned or fresh.
As Barrett said, “The point is to eat vegetables and fruits, fresh or frozen, canned or dried, all have nutritional value.”
