Recently, a friend asked, “Someone gave me some freeze – dried fruit snacks, and my child fell in love with them right away. People always say that we should eat fresh fruits, as once they are processed, there is little nutrition left. Even if dried fruits can still retain dietary fiber and minerals, at least vitamins and health – promoting components are lost, right? Are freeze – dried fruits a waste of money? They are so expensive. Can they really supplement nutrition? Is it appropriate to give this kind of snack as a New Year’s gift? Is it considered a healthy food?”
Actually, if it’s inconvenient or not enough to eat fresh fruits, or if there are other concerns, freeze – dried fruits can be used to supplement fruit nutrition. Of course, they also taste great as snacks. Today, let’s introduce and analyze these increasingly popular freeze – dried fruits in the past two years. Are they really healthy foods?
How Are Freeze – Dried Fruits Made and Why Is the Cost Relatively High?
The so – called freeze – dried fruits are made through the vacuum freeze – drying process. Usually, drying food requires heating. Why can food still dry in a frozen state? As people who have studied physics know, water has a phase diagram. In a frozen state, a small number of water molecules will directly fly out of the ice and turn into water vapor. This change is called sublimation.
The vacuum freeze – drying equipment first freezes the fruit to a very low temperature of minus 30 to 40 degrees Celsius, filling the food with many tiny ice crystals. Then, the air is pumped out to reduce the air pressure. The water vapor generated by the sublimation of ice crystals is also continuously pumped out, so the balance between the ice and vapor phases tends to produce water vapor.
In this way, the ice crystals in the food continuously turn into water vapor at a low temperature. After dozens of hours, the food becomes dry.
Since the ice crystals directly turn into vapor without going through the liquid water state and quietly leave the food matrix, many voids are left inside the food, resulting in a crispy texture when eaten.
Both freezing and vacuum – pumping are required, so this process is very power – consuming and has a higher cost than other dehydration processing methods such as sun drying, hot – air drying, infrared drying, microwave drying, and low – temperature frying.
However, there are rewards for the investment.
Freeze – Dried Fruits Preserve Nutrition Well: “Vacuum – Pumping” Prevents Oxidation and “Low Temperature” Prevents Heat – Sensitive Vitamins
Vacuum – pumping solves the problem that many nutrients and antioxidant components are prone to oxidation during the processing. For example, nutrients such as vitamin C, vitamin A, vitamin E, and folic acid, as well as antioxidant components such as anthocyanins, flavonoids, and carotenoids, are all afraid of oxidation.
Low – temperature freezing solves the problem that some vitamins and phytochemicals are afraid of heat. As we all know, vitamins such as vitamin C, vitamin B1, and folic acid, as well as health – promoting components such as anthocyanins and glucosinolates, are afraid of heat.
Since there is no boiling process, there is no loss of water – soluble health components such as vitamin C, various B – group vitamins, anthocyanins, flavonoids, and chlorogenic acid due to dissolution in water.
Since there is no frying process, there is also no loss of fat – soluble health components such as carotenoids and vitamin K due to dissolution in oil.
Because it is dry enough to inhibit the growth of microorganisms, there is no need to add preservatives.
Note: Freeze – Dried Fruits Are Prone to Moisture and Should Not Be Confused with Low – Temperature Fried Fruits and Vegetables or Sugar – Containing Dried Fruit Products
However, due to their many voids, freeze – dried foods are very prone to absorb moisture. If porous foods are left at room temperature for a long time and come into contact with oxygen, they will also oxidize relatively quickly.
Therefore, freeze – dried foods are usually packaged in vacuum – filled nitrogen, light – proof, and oxygen – isolated packages. They should be eaten up quickly after opening.
It should also be noted that many people mistake low – temperature fried fruit and vegetable chips for freeze – dried fruit and vegetable products. In fact, they are completely different.
Low – temperature fried fruit and vegetable chips are produced by frying in a vacuum state. Vacuum – pumping reduces the pressure. According to the laws of thermodynamics, the boiling point of oil will drop significantly and can even be lower than 100 degrees Celsius.
This low – temperature frying method can greatly reduce the oxidation and polymerization of oil, avoid the production of carcinogens such as benzopyrene, and slow down the Maillard reaction. It can also well maintain the original color of fruits and vegetables and reduce the loss of aroma due to heat.
However, it is still a heating method, which will inevitably cause the loss of vitamins. With a large amount of oil, part of the carotenoids and chlorophyll will also be lost.
Most importantly, the low – temperature frying method will greatly increase the fat content of fruit and vegetable foods.
As we all know, fruits and vegetables are classic low – fat foods, and the fat content of most fruits does not exceed 1%. However, once made into low – temperature fried “fruit chips”, the fat content can reach more than 10%, and even up to 30%, turning them into high – calorie and high – fat products! Therefore, when buying dried fruit and vegetable products, please look carefully at the ingredient list and the nutrition facts label.
In addition, check if there are various sugars and sweeteners in the ingredient list. Unless for some particularly sour fruits (such as sea buckthorn, prickly pear, lemon, cranberries, etc.) that need a little sugar for flavoring, the ingredient list of freeze – dried fruits should preferably only have “a certain kind of fruit” as the only ingredient. Such products have the highest nutrient density.
People with Poor Stomachs, Diabetes, etc. Can Eat Them, and They Are Also Suitable for People with Small Appetites and Busy Work
Who is suitable for eating freeze – dried fruits?
First, people with poor stomachs Vacuum – freeze – dried fruits are more friendly to the stomach and intestines, solving problems such as being afraid of the cold when eating fruits before meals, being afraid of the cold when eating fruits in the morning, and fruits hurting the stomach. At the same time, it largely avoids the loss of nutrients caused by boiling fruits and the additional sugar from boiled fruits.
For example, my intestines are relatively sensitive. After eating a fresh apple, I can feel my stomach gurgling with bowel sounds. When eating sun – dried apple slices, I find them difficult to digest and feel uncomfortable in my stomach because of their tough texture. But when I eat one or two handfuls of freeze – dried apple slices, these problems don’t occur.
One possible reason is that after freeze – drying, the apple slices form a porous structure, which allows digestive juices to fully contact them, making them easier to digest.
Another possible reason is that after freeze – drying and storage for a period of time, most of the proteases in fresh fruits are inactivated, reducing the damage to the surface mucosa of the digestive tract.
The third reason is that there is no need to eat a whole fruit when it comes to freeze – dried fruits. Eating a small handful or a small bag at a time, with a limited total amount, will not cause trouble to the intestines.
Second, people with large or small appetites We often hear some people complain, “I have a small appetite and can never finish a big Fuji apple at one time. I don’t know how to store the remaining half.” Others say, “I’m so gluttonous that I can’t stop eating all kinds of snacks. Eating too much will make me gain weight.” Freeze – dried fruits as snacks can solve these problems. Since each pack of freeze – dried fruits is small in quantity and relatively expensive, it’s unlikely to overeat. Replacing cookies, pastries, potato chips, etc. with small packs of freeze – dried fruits can reduce calories significantly. They are both healthy and delicious, and can prevent overeating.
Third, people with busy daily work For people with extremely busy work, they may not have time or may simply forget to buy and eat fruits in their daily lives. Some people also find it inconvenient to bring fruits to work. For these problems, freeze – dried fruit slices are a good choice. They can be eaten right after opening the package at any time. They can be eaten all year round, and their nutritional value is not much different from that of fresh fruits. As a healthy snack, they are a very good option, better than low – temperature fried fruit and vegetable chips, and much better than cookies, cakes, and potato chips.
Fourth, diabetic people Based on our research on freeze – dried apples and freeze – dried dates, these products are relatively friendly to diabetic patients. Calculating the glycemic index values, we found that the glycemic index of freeze – dried dates is 65, while that of fresh dates is 75; the glycemic index of freeze – dried apples is 52, while that of fresh apples is 51. It can be said that freeze – dried fruits can be safely consumed by diabetic patients (data to be published).
Some friends may ask, “I heard that the glycemic index of apples is only 36. Why has it become 51?” That’s because the apples measured back then did not have as much sugar and as little acid as the current apples. Sugar can increase the glycemic index, while organic acids and polyphenols can decrease it. Most of today’s fruit varieties are being updated to have more sugar, less acid, and less astringency, so the blood – sugar response will naturally increase. Unfortunately, consumers just like this taste.
In conclusion, sugar – free freeze – dried fruits are a good thing and are relatively healthy as snacks. Their main problem is the relatively high cost. Whether to choose them depends on whether you can eat enough fresh fruits and your perception of cost – effectiveness.