Are frozen vegetables worse than fresh? The answer surprises a lot of people

Vegetables start "running down" the moment they leave the soil

Picked vegetables are still alive. They keep breathing and burning the energy stored inside. And along the way, they slowly lose some nutrients.

The biggest losses are vitamin C and some B vitamins. They dissolve in water and break down easily with heat, light and oxygen.

Picture the journey of a bunch of greens at the market:

1. Picked early in the morning at the farm.
2. Loaded onto a truck, taken to the wholesale market.
3. Laid out at a stall, in Ho Chi Minh City temperatures of about 30 to 35°C.
4. You buy it and keep it in the fridge for a few days.

At every step, the bunch loses a little more. Some studies report that spinach kept at room temperature can lose most of its vitamin C in just a few days.

Freezing: pressing the "pause" button

Commercial frozen vegetables usually go through a process like this: harvest, wash, blanch quickly in boiling water or steam, then freeze very fast. All of it often within a few hours.

Blanching sounds like it would strip nutrients, and it is true that a little vitamin C and B vitamins leach into the blanching water. But it does an important job: it switches off the enzymes in the vegetables. Without blanching, those enzymes quietly keep changing the color, smell and nutrients, even in the freezer.

After that, deep-freeze temperatures almost stop every reaction. Just like the frozen rice we described in cold rice and resistant starch: fast freezing is pressing pause.

The comparison: a draw, and sometimes frozen wins

Scientists at the University of California reviewed many studies, then ran their own comparison of fresh produce, fresh produce stored in the fridge for 5 days, and frozen produce.

A summary of what they found:

As for fiber, you can relax. Freezing does not remove fiber. Ice crystals can break some cell walls so the vegetables turn softer, but the amount of fiber stays the same.

When to choose fresh, when to choose frozen?

Fresh vegetables are still wonderful, especially when:

• You buy and cook them within a day or two.
• They are eaten raw, like lettuce, fresh herbs and cucumber. Freezing makes them mushy and not fit for eating raw.
• They are in season at your local market, both tasty and cheap.

Frozen vegetables are handy when:

• You shop once for the whole week.
• You want peas, beans and corn like green peas, edamame and sweet corn. They lose their sweetness fast after harvest; see what is in green peas.
• You are having a busy day, so your meal still has vegetables instead of skipping them.

What matters is not fresh or frozen, but whether you eat enough vegetables. A bag of frozen vegetables that actually gets eaten is always better than a bunch of fresh greens that wilts in the fridge and gets thrown away.

How to cook frozen vegetables so they taste good

• Do not thaw leafy greens and small vegetables first. Put them straight into a hot pan or pot. Long thawing makes them watery and mushy.
• Cook briefly. They are already blanched and only need heating.
• Use little water. Stir-fry, steam, or add at the end of a soup. Boiling in lots of water loses more vitamin C.
• Dishes that were fully cooked before freezing (like ready-cooked beans) can simply be thawed overnight in the fridge and eaten.

Frequently asked questions