There’s a tiny bit of summer left, and the more cautious have already started preparing all sorts of seasonal and useful winter goodies. Alas, traditional jam raises many questions due to a large amount of sugar and long cooking.
An alternative is to freeze vegetables and berries. Fortunately, this method of storage has been studied in detail. Here is what we know so far.
Are the active substances preserved when the berries are frozen?
The short answer is yes.
For example, ascorbic acid (AA – ascorbic acid), one of the most unstable vitamins, keeps better in frozen foods than at room temperature. And if you need to reheat food, it is advisable to limit yourself to low temperatures (up to 70 degrees Celsius inclusive).
Scientists were also interested in the quality of preservation of useful components of berries during long-term storage in frozen form. Vitamin C, polyphenols and antioxidants researched in blueberries, raspberries and blackberries, industrially frozen and stored at -18.
4 months after freezing, the content of the studied nutrients and the color of the berries did not change (in our conditions it is late autumn-early winter). After 6 months, the maximum losses amounted to 23% of useful substances.
After 10 months (i.e. the following summer), the polyphenol content decreased by 28-47%. Anthocyanins were preserved at 80–91%, and ascorbic acid at 62–76%. Most antioxidants were retained in blueberries (77%), the least – in raspberries (63%).
That is, even next summer your frozen berries will be 2/3 as good as fresh.
Why not make jam?
First, the sugar. We have already written about this separately. And the jam contains at least 50% pure sugar. Plus the fructose of berries or fruits – and 10, maximum 12 teaspoons (without slide!) of jam completely cover the daily need for fast carbohydrates.
Given their inevitable food intake, jam should be limited to a few teaspoons a day.
On the other hand, jam is a long, very long cooking of unfortunate berries. As long as the components look like berries, and the composition is syrup. So when heated for 90 minutes at 70 degrees Celsius in pomegranate juice, 69% of vitamin C and 90% of polyphenols were destroyed. And we boil the jam.
On average, 16% of vitamin C is lost during normal cooking. Vitamins A, D, E, H, B2, B3, B12 are more stable, but some of them can be destroyed by light. Here you will find data on the stability of nutrients and their degradation under the influence of different processing methods.
Another advantage of the frozen fruit piggy bank is that they are an excellent source of macro and microelements. 100 grams of frozen fruit can provide 0.2-2.8% of an adult’s (31-50 years old) daily macronutrient requirement and 2.5-100% micronutrient requirement.
In addition, frozen berries may be safer than fresh ones – for example, the number of methicillin-resistant staphylococci (pathogenic bacteria resistant to most antibiotics) decreases during freezing and subsequent storage.
But what about vegetables?
Vegetables are the same as berries. They retain nutrients well when stored frozen.
In the study of industrially frozen green beans, asparagus and zucchini, it was found that freezing for 2 months did not affect the vitamin and antioxidant content. The content of chlorophyll, ascorbic acid, polyphenols and lutein (the yellow pigment of the group of carotenoids, an antioxidant, involved in visual acuity) was evaluated.
Additionally, pre-blanched vegetables, especially green beans and zucchini, contained even more bioavailable substances than raw ones.
Analysis of the vitamin C, E, B2, and carotene content of corn, carrots, broccoli, spinach, green beans, peas, strawberries, and blueberries showed that compared to fresh produce :
- vitamin C contained in the same or more
- there was more vitamin B2 in frozen broccoli than in fresh; in peas – less. In other vegetables and berries, the vitamin was the same.
- vitamin E was the same as fresh except for three samples
- carotene was fully retained in spinach and green beans, in smaller amounts relative to fresh in peas and carrots, and completely broken down in blueberries, strawberries, and corn.
Analyzing the publications made before 2019 on the long-term storage (more than 6 months) of vegetables at temperatures below -18 degrees, the authors come to the conclusion that this storage method can be recommended as practical and effective. Despite the partial loss of nutritional value, most of the nutrients in vegetables are retained.
How to prepare berries and vegetables for freezing?
In scientific publications, to determine the safety of vitamins and antioxidants, products are frozen by the industrial method – individual quick freezing were used.
At the same time, small berries are laid out in a single layer on a special grid, after which they are placed in freezers and blown with cold air. Thus, the berries completely freeze in a few minutes and do not have time to lose vitamins. Larger fruits or vegetables are pre-chopped.
At home, it is impossible to achieve such rapid freezing, but you can speed it up as much as possible under the existing conditions – freeze food in small batches, lay it out in a thin layer and chop large ones.
It also helps to improve the retention of vitamins and antioxidants. whiten hard-skinned vegetables and berries before freezing them (one, two, three).
To do this, boil them for 2-5 minutes (the larger and denser the product, the longer it is), then cool in ice water. You can steam them – then blanching will take 4-8 minutes. It takes about the same time to cool as to blanch.
Spinach and greens can simply be poured with boiling water and cooled in cold water.
Total: Grandmothers go to a new level
Our grandchildren won’t leave us canned pickles, but packets of frozen vegetables and berries 🙂
Freezing is a great alternative to traditional storage methods. Even after 6-10 months from the moment of freezing, about 2/3 of the vitamins, antioxidants, and other benefits are retained in the berries.
Fruits, berries, and vegetables are stored just as well. For maximum preservation of vitamins, it is advisable to freeze products in a thin layer and in small quantities and pre-blanch vegetables.
And freezing is easy. No worries with syrup, jars, and boiling for several hours. Washed, dried, laid out – ready. And in winter you have lovely strawberries and raspberries for breakfast.
Industrially frozen vegetables and fruits are also a good option. They retain almost all the vitamins and antioxidants compared to fresh ones. The main thing is that they are not thawed during storage.