Is vitamin C lost in freezing?

October 12, 2025 •

4 min read

Research indicates that flash-frozen vegetables can sometimes contain more nutrients than fresh counterparts that have been stored for several days in a refrigerator. This surprising fact challenges the long-held assumption that vitamin C is lost in freezing, revealing a more nuanced truth about how freezing impacts nutritional value.

Quick Summary

Freezing is an effective method for preserving nutrients in produce, but some vitamin C is lost during the pre-freezing process of blanching vegetables. Overall, frozen items often have a comparable, and in some cases, higher vitamin C content than fresh produce that has been subjected to nutrient degradation over time and during transport.

Key Points

Initial Loss vs. Long-Term Gain: While some vitamin C can be lost during the initial processing (especially blanching), the freezing process stops further nutrient degradation, meaning frozen produce often retains more vitamin C than fresh produce stored for several days.
Blanching is the Main Culprit: The brief boiling step (blanching) used for many commercially frozen vegetables is the primary cause of any vitamin C leaching, as the nutrient is water-soluble.
Fruits Retain More: Frozen fruits typically do not undergo blanching and therefore retain a much higher percentage of their original vitamin C content than vegetables.
Smart Cooking Preserves Nutrients: Steaming or microwaving frozen produce is better for retaining vitamin C than boiling, as less of the water-soluble nutrient leaches into the cooking liquid.
Storage Conditions Matter: Keeping your freezer consistently cold (below -18°C) and using airtight packaging prevents further nutrient loss and freezer burn over time.
Overall, a Great Choice: Frozen produce is a convenient, cost-effective, and highly nutritious option for year-round access to vitamins, often rivaling or exceeding the nutritional value of stored fresh alternatives.

The Science of Freezing and Nutrient Retention

The notion that frozen food is less nutritious than fresh is a widespread misconception. The key factor is timing. Fresh produce begins to lose vitamins and minerals almost immediately after being harvested, a process accelerated by exposure to light, heat, and air. Freezing, especially the rapid flash-freezing used commercially, effectively puts a pause on this degradation. By chilling food to below 0°C, the enzymes that cause food to ripen and decay are deactivated, and the growth of microbes is halted, locking in the majority of nutrients.

The Critical Role of Blanching

For many vegetables, the commercial freezing process involves a pre-treatment step called blanching. This is a brief immersion in boiling water followed by a quick cool-down in ice water. While blanching is crucial for inactivating enzymes that can cause unpleasant changes in color, flavor, and texture during long-term freezing, it is also the primary source of initial vitamin C loss in frozen vegetables. As a water-soluble vitamin, some of the ascorbic acid (vitamin C) leaches into the boiling water. The extent of this loss can vary significantly depending on the type of vegetable and the blanching duration, ranging from 10% to 50% or more.

However, it is important to remember that most fruits are not blanched before freezing. For example, frozen berries are typically washed and frozen directly, meaning they retain very high levels of their original vitamin C content.

Frozen vs. Fresh: A Comparative Look

When comparing fresh and frozen produce, the comparison is rarely between fresh-from-the-field and frozen. A more realistic comparison pits frozen produce against the fresh produce that has been transported to a supermarket and then stored in a home refrigerator for several days. During this period, the fresh produce's vitamin content continuously declines. Studies have shown that after just a few days of storage, frozen versions of items like peas and spinach can have higher levels of vitamin C than their refrigerated counterparts.

The Impact of Storage Time and Conditions

Even in the freezer, nutrient degradation is not completely stopped, but it is dramatically slowed. Over very long storage periods (e.g., more than a year), some nutrient loss can occur. The key to maximizing retention is proper storage: using airtight, high-quality packaging to prevent freezer burn and maintaining a consistent, low temperature below -18°C.

The Role of Cooking Methods

How you prepare your frozen produce after thawing also has a major impact on its final vitamin C content. As a water-soluble vitamin, cooking methods that involve simmering in water can cause further leaching of vitamin C.

Best Cooking Methods: Steaming, microwaving, and sautéing with minimal water are all excellent ways to cook frozen vegetables and retain vitamins. Steaming, for instance, can help retain up to 90% of vitamin C.
Worst Cooking Methods: Boiling can cause up to a 50% loss of vitamin C and other water-soluble nutrients.

Comparison Table: Nutrient Retention by Processing Method


Feature	Fresh (After 3-5 Days Storage)	Frozen (Commercially)	Canned (Commercially)
Harvest Time	Varies; can be several days before consumption.	Typically flash-frozen at peak ripeness, within hours of harvest.	Harvested at peak ripeness and processed immediately.
Initial Vitamin C Loss	Continuous degradation over time.	Small initial loss during blanching of vegetables.	High loss due to high-heat processing.
Overall Nutrient Value	Can be lower than frozen over time, especially for water-soluble vitamins.	Retains nutrients effectively, often surpassing stored fresh produce.	Significant nutrient loss, especially heat-sensitive vitamins like C.
Long-Term Storage	Perishable within days or weeks.	Maintains nutrients for 6-12 months or longer.	Extended shelf life (1-5 years).

Maximizing Vitamin C from Frozen Produce

To ensure you are getting the most nutritional value from your frozen fruits and vegetables, follow these key steps:

Buy High-Quality: Choose brands that use flash-freezing and minimal processing for better nutrient retention.
Store Correctly: Keep your freezer at or below -18°C and use airtight packaging to prevent nutrient degradation and freezer burn.
Avoid Thawing: For most vegetables, cook them directly from frozen. Thawing can lead to further nutrient breakdown.
Choose Smart Cooking Methods: Steam or microwave rather than boil to minimize water-soluble vitamin loss.
Use Promptly: While frozen produce lasts a long time, consuming it within the recommended 6-12 month timeframe will ensure peak nutritional quality.

Conclusion

So, is vitamin C lost in freezing? The short answer is yes, some initial loss can occur, particularly for blanched vegetables. However, freezing is a highly effective method of preservation that stabilizes and locks in the remaining nutrients. When compared to fresh produce that has been stored for several days, frozen fruits and vegetables often emerge as the more nutritious option. By understanding the process and choosing smart cooking methods, you can confidently enjoy frozen produce as a healthy and convenient part of your diet. For more science-based nutritional information, consider exploring resources from the National Institutes of Health.(https://pmc.ncbi.nlm.nih.gov/articles/PMC7767136/)

Frequently Asked Questions

Yes, freezing is an excellent way to preserve most nutrients. It effectively halts the enzymatic processes that cause nutrient degradation, meaning that produce frozen shortly after harvest can be nutritionally comparable to or even more potent than fresh produce stored for several days.

For many vegetables, the initial loss of vitamin C is not from the freezing itself, but from the required pre-treatment called blanching. This process, which involves a brief dip in boiling water, can cause water-soluble vitamin C to leach out.

No, most frozen fruits do not undergo blanching. They are typically flash-frozen raw, which means they retain a very high percentage of their original vitamin C content.

While freezing significantly slows nutrient loss, it doesn't stop it completely over very long periods. However, the rate of loss is much slower than in fresh produce. For best quality, it's recommended to consume frozen produce within 6 to 12 months.

To retain the most vitamin C, it is best to cook frozen vegetables using methods that minimize contact with water. Steaming and microwaving are excellent choices, as is sautéing with minimal liquid. Avoid boiling, which can cause significant nutrient loss.

Generally, yes. Canned foods are exposed to high-heat processing, which can destroy up to 85% of their vitamin C. Frozen produce retains a much higher percentage of the nutrient.

For most frozen vegetables, it is best to cook them directly from frozen. Thawing them beforehand can lead to a mushy texture and potentially more nutrient loss.