I guess that when we think of the many health benefits of fruit, most people would assume that fresh fruit was a much healthier option than the frozen variety. While this may be true much of the time, fresh fruit is not always in season. Where I live, fresh strawberries are only available for one or two months of the year and I am forced to make do with the frozen kind.
When it comes to blueberries, I cannot remember the last time I was able to buy them fresh. The frozen variety does a great job when it comes to flavor and our family gets through plenty of them each month. But how do frozen blueberries stack up when it comes to their health benefits?
Blueberries are the second most popular berry in the United States. No prizes for guessing which berry is more popular. Second only to strawberries, blueberries are firmly established in second place well ahead of raspberries and blackberries.
Blueberries are a great addition to your breakfast cereals, oatmeal or smoothies. They are popular both for their flavor and also their much vaunted health benefits. While strawberries may be the most popular of all the fresh berries, it is likely that far more frozen blueberries are sold than frozen strawberries.
Frozen Blueberries Compared with Fresh Blueberries
Bearing in mind that frozen blueberries are so popular, we feel it is worth exploring their benefits or otherwise compared with the fresh variety.
Some things do not Change
Frozen fruit is not boiled or blanched prior to being processed. So long as you let them thaw naturally, they are still regarded as a raw food.
While the freezing process does have some marked effects, there are certain things that do not change at all. Whether you are eating the frozen or the fresh variety, the following will be exactly the same.
- Calories remain the same at around 84 calories a cup.
- Mineral content also remains exactly the same. Blueberries contain manganese, potassium, iron, magnesium, phosphorus, zinc and calcium. The percentage of daily value that you get from them will not change.
- Fiber and protein remain the same at 4 grams and 1 gram per cup respectively.
What Changes when Blueberries are Frozen?
The simple answer is antioxidants and vitamins. Both are sensitive to oxygen, light and heat. Some can deteriorate almost as soon as the berries are plucked.
A study published by England’s Chester University in 2013 did a great job of analyzing the benefits of frozen blueberries and some of the results may surprise you. (1) The full report is linked at the bottom of this article but this is a summary of their findings.
1. Vitamin C
Vitamin C is one of the best known antioxidants among the general public. The vitamin C content of fruit and veg is a major factor in people’s dietary decisions. The surprising news for those of you with concerns is that there is actually more vitamin C in a frozen blueberry than the fresh berry.
When blueberries are very fresh, they contain only a little less vitamin C than frozen berries but after they have sat in your refrigerator for a few days, they will give you a massive 67% less of the vitamin than the frozen.
How can we explain this? The reason is that fresh berries are picked before they are fully ripe arriving in the supermarket with a ripe appearance. This means they look great but they were at their antioxidant peak while still attached to their bush.
After picking them, they begin to deteriorate and die. Unlike fresh berries, frozen blueberries are picked when they are at their peak level of ripeness which makes sense since they can’t continue to ripen at freezer temperatures.
So why is the vitamin C content so low at day three? Well, it has something to do with a process known as respiration. Despite being kept cool in the fridge, the berries actually continue to burn up their nutrients in an effort to stay alive.
Chemical bonds get broken including vitamins and polyphenols. Oxygen, light and temperature all influence respiration and your fridge typically minimizes all three. Unfortunately, the temperature is too high to prevent respiration entirely and plenty of oxygen continues to circulate.
If you have never heard of them or the term is familiar but you do not know what they are then let me explain. Anthocyanins are a type of water-soluble pigment responsible for giving fruit and veg and plants their rich purple, blue and red colors.
If you have ever been told that eating colorful fruit is good for you, then anthocyanins are a major reason why this is true. They are a very powerful class of antioxidant and the nutrient for which blueberries are probably best known. They have also been extensively studied with regard to their health benefits.
The levels of anthocyanins in frozen blueberries compared to the fresh variety follow a very similar pattern to vitamin C levels. Just like vitamin C, the amount of anthocyanins degrades over time but the degradation after three days is even more dramatic.
Another major mark in the book for frozen blueberries.
When it comes to the total polyphenol content of both types of blueberry, we see some very interesting results. These results are actually an outlier when it comes to frozen food. We usually see that fruits, and vegetables for that matter, have a greater nutritional value fresh compared to those left in the fridge for three days or so. In the case of blueberries however, the polyphenol content increases through the first three days.
These findings are related to the respiration process mentioned earlier in which the berries strive to stay alive. However, despite the increase in polyphenol levels in the fresh berries, they still lag behind the polyphenol content of the frozen type since they were allowed to fully ripen before being picked.
When it comes to lutein, you are better of going fresh. This fat-soluble nutrient is a type of carotenoid which typically degrades considerably slower water-soluble nutrients like vitamin C or anthocyanins.
This explains the results of the study which demonstrate that the lutein content holds up well over the duration of a few days. Lutein may also be sensitive to the process of freezing the fruit which destroys much of the content.
Having said that, blueberries contain very little lutein to begin with and the large difference between the lutein content of fresh blueberries compared with frozen should not be weighed so heavily.
Yet another Advantage of Frozen Blueberries
Now that we have established that frozen blueberries may be even better for you especially when it comes to antioxidant and vitamin content, let us take a look at another benefit.
Even during the period when blueberries are in season, many people will still opt for the frozen variety. The type of fresh blueberry typically sold are conventional, cultivated berries. These are the type that have been cultivated for many generations in order to appear more pretty and plump.
Unfortunately they also have a much lower antioxidant content than wild blueberries. In terms of the ORAC ratings, wild blueberries have around double the value compared with conventional store bought berries.
While wild blueberries are rarely sold in western stores fresh, they are usually readily available frozen at various supermarkets.
If you have opted for the frozen fruit, do not put them in your microwave to thaw them out. It is much healthier if you simply plop them into a dish in the fridge before bedtime.
By morning, they will have thoroughly thawed out yet retain their freshness ready for you to use in your cereal, oatmeal or drink.