How long do frozen blueberries last once thawed? (3 tips)

In this article, we will answer the question “How long do frozen blueberries last once thawed?”. We will discuss what is the shelf life of blueberries and what affects the shelf life of thawed blueberries. Moreover, we will talk about how you can freeze blueberries, what are the effects of freezing and thawing blueberries, and how you can properly thaw blueberries.

How long do frozen blueberries last once thawed?

Frozen blueberries that were thawed in the refrigerator can last for up to 5 days. However, the quality of the blueberries may degrade during this period. The freezing and subsequent thawing process causes cellular damage to the fruit’s structure, making it more susceptible to microbial contamination and quicker spoilage. So, after thawing, the berries should be promptly consumed or used within approximately 5 days (1,2).

What is the shelf life of blueberries?

Blueberries have a two-day shelf life at room temperature, which normally varies between 68 °F and 72 °F (20 °C and 22 °C) (3,4). 

The refrigerator, with its regulated low-temperature environment, is a good alternative for extending blueberry freshness. When kept in the refrigerator, fresh blueberries can live for up to 10 days (3). This temperature range slows enzymatic responses and microbial development within the fruit by minimizing metabolic activities. However, to maintain the correct humidity level and prevent excess moisture accumulation, blueberries should be stored in a well-ventilated container or perforated plastic bag (2,3). 

When frozen at temperatures below 0 °F (-18 °C), fresh blueberries can keep their freshness for up to 6 months. Freezing halts enzyme activity, microbial development, and oxidation, successfully preserving nutritional content and flavor (2).

What affects the shelf life of thawed blueberries?

Cellular damage

When blueberries are frozen, ice crystals develop within their cellular structure, causing physical injury to the fruit. These ice crystals break down upon thawing, causing cell membranes to shatter and cellular contents to be released. This damage makes the berries more susceptible to enzymatic reactions and microbial multiplication, hastening their demise (2,5).

Microbial Activity

As blueberries thaw out, any lurking microorganisms on their surface or nestled within their flesh spring back to life. This resurgence of life includes bacteria, molds, and yeasts, and they can thrive in moisture-laden conditions, ultimately causing the berries to spoil. That’s why it’s crucial to gobble up thawed blueberries within a relatively short time, usually within 5 days, when you keep them in the fridge (6).

Oxidation

During the thawing process, exposure to air can cause oxidation, resulting in changes in color, taste, and nutritional value. Blueberries’ naturally occurring antioxidants may become less efficient with time, reducing their health advantages (6).

Temperature Fluctuations and Cellular Damage

Temperature fluctuations, particularly when blueberries are subjected to repeated cycles of freezing and thawing, can have serious effects on the fruit’s cellular structure. These phenomena are explained by the laws of thermal expansion and contraction. These temperature variations can worsen cellular injury, leaving the fruit more prone to enzymatic responses and microbial development. It’s essentially like putting the blueberries in a succession of mechanical shocks, which can accelerate their total degeneration (7,8).

Moisture Loss

Thawed blueberries can lose moisture faster than fresh blueberries, resulting in dryness and a loss of juiciness. This can have an effect on the texture and overall quality (9).

How can you freeze blueberries?

Blueberries may be frozen properly to preserve their cellular integrity and nutritional value. The initial pre-freezing phase, which involves spreading blueberries on a tray and exposing them to sub-freezing temperatures, is critical. Water within the berry cells begins to freeze at this phase, forming little ice crystals. These early ice crystals are critical because they decrease the possibility of bigger ice crystals later forming, which might tear cell walls and result in mushy berries when thawed (2).

In addition, it is necessary to package blueberries in sealed containers or freezer bags. By forming a barrier, it reduces the fruit’s exposure to oxygen, which can cause oxidative processes that eventually cause the fruit’s quality and nutritional value to decline. By including the freezing date on the label, it is easier to keep track of the berries’ freshness and make sure they are used within the suggested storage period (2).

In order to preserve food, the freezer must be kept at a constant, extremely low temperature, ideally below 0 °F (-18 °C). This temperature slows enzyme activity, microbial development, and the generation of big ice crystals, all of which might harm the berry’s flavor and structure (2).

What are the effects of freezing-thawing blueberries?

Blueberries’ flavor and texture may be impacted negatively by the freezing and thawing processes. The following are some typical negative effects of freezing and thawing blueberries:

Softening

Blueberries tend to get softer when they thaw, and this happens because of how freezing affects them on a scientific level. When blueberries are frozen, tiny ice crystals form inside the fruit, and these ice crystals can actually damage the cell walls. As the blueberries thaw, these ice crystals melt, leading to the fruit’s cell membranes breaking. This is what makes the berries softer, as their internal structure gets compromised (5,9).

Loss of flavor

Another thing to note is that freezing can impact the taste of blueberries. Some of the components that give blueberries their delicious flavor, like sugars, acids, and compounds that create their scent, can be influenced during freezing. This happens because the freezing process can disrupt the balance of these flavor compounds. So, when you thaw frozen blueberries, you might notice a loss of flavor and aroma, which can modify how they taste (5,7,8).

Loss of nutrients

Freezing can also have an effect on the nutritional content of blueberries. Vitamin C and antioxidants are two examples of healthy substances and vitamins that may be sensitive to temperature fluctuations (10).

Therefore, these elements may gradually disintegrate when blueberries are frozen, thereby lowering the fruit’s total nutritional content. It’s a good idea to carefully store frozen blueberries and utilize them within a fair amount of time in order to reduce this loss (9,10).

Excess of moisture

Last but not least, blueberries defrost and release moisture. This occurs as a result of the fruit’s cell walls disintegrating during freezing and thawing. The berries may become softer and more prone to deteriorating as a result of the additional moisture (9,10).

This is a normal part of the freezing and thawing process, that’s why it is important to treat thawed blueberries carefully to preserve their best texture and freshness (9,10).

How can you properly thaw blueberries?

Blueberries must be carefully thawed in a controlled environment to prevent cellular damage and preserve quality. It is advised to gradually defrost food in a refrigerator, where the temperature is constant and cold. This gradual defrosting lowers the possibility of cell rupture and textural alterations by preventing the quick growth of ice crystals inside the berry cells (2,11).

To do so, just move the frozen blueberries from the freezer to the fridge and let them defrost there for a few hours or overnight. Avoid utilizing higher temperatures or microwave thawing techniques since they may result in uneven thawing, moisture loss, and possible cellular damage (2).

According to science, this careful process guarantees that the blueberries keep their flavor, texture, and nutritional content, making them appropriate for a variety of culinary uses (2,11).

You can refreeze the blueberries after fully thawed, but only if they are thawed in the refrigerator (2).

How can you tell If blueberries have gone bad?

Identifying spoiled blueberries is not just a matter of preference, but a scientific approach to food safety and quality (4,6).

• When you see juices oozing from squishy blueberries, it’s a sign of damaged cell membranes and potential microbial contamination, making it wise to discard them.
• Mold growth, regardless of its color, should be a red flag, as molds produce mycotoxins that can pose health risks. Some species of mold causing blueberry spoilage include Botrytis cinerea (gray mold) and anthracnose (ripe rot, Colletotrichum gloesosporiodes).  
• Changes in texture, like mushiness, wrinkles, or dehydration, occur due to enzymatic reactions and moisture loss, rendering the berries unfit for consumption.
• A foul smell is a clear indication of spoilage, often stemming from spoilage microbes and decay.
• If in doubt about expired blueberries, a taste test can reveal any off-flavors, which signal spoilage.
• When it comes to freezer burn, it doesn’t make them unsafe, but the quality diminishes due to moisture loss and oxidation, so it’s a personal choice whether to use them or not.

Conclusion

In this article, we answered the question “How long do frozen blueberries last once thawed?”. We discussed what is the shelf life of blueberries and what affects the shelf life of thawed blueberries. Moreover, we also talked about how you can freeze blueberries, what are the effects of freezing and thawing blueberries, and how you can properly thaw blueberries.

References

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