Does frozen kale still have nutrients?
Kale has become one of the most popular superfoods in recent years. Its dense nutrient profile and versatility have made it a staple vegetable for health-conscious eaters. While fresh kale is packed with vitamins, minerals, and antioxidants, many people opt for the convenience of frozen kale. But does freezing affect the nutrient content of kale? Keep reading to find out.
Nutrients in Kale
Kale is often referred to as a nutritional powerhouse, and for good reason. One cup of raw kale contains:
- 33 calories
- 6 grams of carbs
- 3 grams of protein
- 1 gram of fiber
It’s also packed with vitamin K, vitamin A, vitamin C, calcium, potassium, magnesium, iron, and antioxidants like lutein and zeaxanthin.
Here’s a more detailed overview of the top nutrients found in kale:
| Nutrient | Amount in 1 Cup Raw Kale | % Daily Value |
|---|---|---|
| Vitamin K | 547 mcg | 684% |
| Vitamin A | 10302 IU | 206% |
| Vitamin C | 80.4 mg | 134% |
| Calcium | 150 mg | 15% |
| Potassium | 299 mg | 9% |
| Magnesium | 23.4 mg | 6% |
| Iron | 1.1 mg | 6% |
As you can see, kale provides substantial amounts of vitamin K, vitamin A, vitamin C, and calcium. It’s also a good source of potassium, magnesium, and iron.
Effects of Freezing on Nutrients
Freezing is one of the best methods for preserving nutrients in vegetables over an extended period. However, the freezing process does result in some changes to the vegetable on a cellular level.
When vegetables are frozen, the water inside the plant cells forms ice crystals. This can rupture cell walls and lead to some loss of water-soluble nutrients like vitamins C and B when thawing occurs.
However, several studies have found frozen vegetables retain most of their nutrients, often more so than fresh vegetables that have been stored for several days.
According to a study published in the Journal of Food Composition and Analysis, freezing resulted in no significant loss of vitamins A, K, B6 or folate in kale. Some loss of vitamin C and lutein was observed after blanching, as well as continued vitamin C loss during frozen storage for 8 months.
However, the frozen kale retained 84-99% of these micronutrients over the length of the study. It also had comparable levels to fresh kale for polyphenols, flavonoids, and glucosinolates like sulforaphane, which provide antioxidant and anti-inflammatory benefits.
Another study in the Journal of Agriculture and Food Chemistry found that frozen kale had similar levels of polyphenols as fresh kale even after 10 months of storage.
Tips for Preserving Nutrients in Frozen Kale
Follow these tips to get the most nutrients out of frozen kale:
- Choose kale that has been blanched or lightly steamed prior to freezing. This deactivates enzymes that can degrade nutrients over time.
- Use frozen kale within 8-12 months for best quality and nutritional value.
- Steam, simmer or sauté frozen kale with minimal water to reduce vitamin losses.
- Consume both the kale as well as the nutrient-rich cooking liquid.
- Add frozen kale at the end of cooking soups, stews or pasta dishes to preserve nutrients.
- Pair frozen kale with foods high in vitamin C like citrus, tomatoes, broccoli or peppers to improve iron absorption.
Frozen vs. Fresh Kale Nutrition
While frozen kale loses some vitamin C and other water-soluble nutrients during blanching and storage, studies show its nutritional value remains comparable to fresh kale overall.
Here is a comparison of the main nutrients found in 1 cup of frozen curly kale and the same volume of fresh raw curly kale:
| Nutrient | Frozen Kale | Fresh Kale |
|---|---|---|
| Calories | 36 | 33 |
| Fiber | 2.6g | 2.6g |
| Protein | 2.2g | 2.5g |
| Vitamin A | 11,034 IU | 10,302 IU |
| Vitamin C | 51.3mg | 80.4mg |
| Vitamin K | 481mcg | 547mcg |
| Calcium | 150mg | 150mg |
While frozen kale has slightly lower vitamin C compared to fresh, it has well retained levels of vitamin K, vitamin A, calcium and other nutrients. It makes for an excellent alternative when fresh kale is not available or practical to use.
Health Benefits
The array of vitamins, minerals and antioxidants in frozen kale can provide many of the same health benefits associated with fresh kale:
- Heart health – The fiber, potassium, folate and vitamin K in frozen kale support healthy circulation and blood pressure.
- Immunity – High vitamin C, A and antioxidant content boost the immune system and help fight infections.
- Strong bones -Frozen kale is high in calcium and vitamin K, both important for bone mineral density.
- Vision health – Lutein, zeaxanthin and vitamin A support eye health and prevent age-related vision issues like cataracts.
- Cancer prevention – Sulforaphane and other compounds in frozen kale exhibit anti-cancer effects.
- Digestion – The fiber content aids digestion and helps maintain regularity.
The bottom line is frozen kale provides nearly the same density of vitamins, minerals and disease-fighting compounds as fresh kale. It makes an easy, nutritious addition to soups, stews, smoothies and side dishes. Just be mindful of sodium content if using commercially frozen varieties. But choosing plain frozen kale and seasoning it yourself is a healthy and handy way to reap the many benefits of this leafy green vegetable.
Conclusion
Kale is one of the most nutrient-dense vegetables you can eat, whether fresh or frozen. While frozen kale loses some vitamin C during blanching and storage, studies show it retains comparable levels of most other vitamins, minerals and antioxidants. Frozen kale makes it easy to add this superfood to your diet year-round. To maximize nutrients, use frozen kale within 8-12 months and cook with minimal water. Pair it with fresh foods high in vitamin C to offset any losses. Overall, frozen kale is nutritionally on par with fresh and delivers a similar wealth of compounds to support heart and eye health, immunity, cancer prevention and beyond.