Freeze-dried food sounds a bit alien, don’t you think? Well, that is precisely because it is. Before freeze-drying entered the culinary mainstream, it was mainly reserved for the production of food for astronauts, the military or food for extreme sports athletes. Nowadays, well-known restaurants and breakfast cereal manufacturers use freeze-dried fruits to obtain colour, texture and additional nutritional value.
But what are lyophilised fruits, and what nutritional value do they possess? The freeze-drying process is a miracle of chemistry, and the result is a fruit product that is healthy and tasty.
What exactly are freeze-dried fruits?
Unlike regular dried fruit (such as grapes, apples, dates, apricots, etc.), lyophilised fruits are initially frozen to -40°C in a vacuum chamber for flash-freezing. Then, with a slow reduction in ambient pressure, the frozen components undergo a chemical transformation from solid to gaseous. The process takes a whole week, and the final products are stored under complete airtightness for preservation. In a nutshell, we can say that these are frost-dried fruits.
Freeze-drying is a unique form of food preservation as it protects the cellular structure and shape of the fruit without significant volume loss. The low temperature also helps to reduce nutrient losses that often occur with air or oven drying.
For the meticulous-minded: the freeze-drying process takes place in three stages. The first stage involves rapid freezing; in the second slow drying occurs, which sublimates the ice components (removes or alters) below ambient atmospheric pressure. The third stage is secondary drying, during which any remaining unbound water molecules are desorbed from the drier parts of the food.
How to use freeze-dried fruits?
Lyophilised fruit is like a concentrated version of the real one. They are crunchy and can quell our (often-occurring) craving for carbohydrates. It’s a bit like flavoured, crisp air. The product is very light and does not have the same chewy texture that you would expect from most traditional dried fruits. It’s something absolutely distinct that makes this product so incredible.
Lyophilised fruit has a broad range of use. Grind them into ice cream or add them to granola. Lyophilised raspberry powder is widely used in restaurants and can also be made at home. Just as with traditional dried fruits, they can be easily transported in luggage. They are ideal as an additive to mixes or for backpacking on long journeys. Furthermore, it is a particularly practical invention for children as it does not leave a sticky feeling. These products also rehydrate, nearly returning to a fresh state, making freeze-dried fruit ideal for smoothies, yoghurt or ice cream.
What products can be lyophilised?
Almost any food can be freeze-dried. Here are a few examples:
- raspberries
- strawberries
- bananas
- apple
- mango
- blueberries
- plums
- sour cherry and morello cherry
- pineapple
- peach
- kiwi fruit
- coconut
- orange
- rhubarb
- blackberries
Are lyophilised fruits healthy?
Thanks to the low freezing temperatures generated through vacuum pressure, freeze-dried fruits retain most of their nutritional value, colour and original shape. All the dietary fibre and approximately 95% of the essential nutrients are retained. This is particularly impressive as water-soluble vitamins such as vitamin C, beta carotene and B vitamins are sensitive to most cooking methods. And what’s the most exciting thing? Unopened, freeze-dried fruit can be stored in the larder for 25 years. Completely free of preservatives.
Health benefits of consuming freeze-dried fruit
Remarkable studies exist on freeze-dried berries, including strawberries, blueberries and black raspberries. The benefits of consuming them involve fighting cancer, decreasing inflammation, enhancing brain performance, supporting insulin function and improving bone and joint inflammation. This is an overview of why freeze-dried fruit is an excellent and healthy snack.
How do you freeze-dry fruits yourself?
Lyophilised bananas or freeze-dried raspberries – how do you make them yourself at home? Sadly, this process cannot be carried out without specialised equipment. To freeze-dry products independently, you should invest in a freeze-dryer. The market offers a range of options, from small to large, and cheaper to more expensive. Your choice of equipment depends entirely on your needs. However, it is indisputable that such equipment requires a substantial financial outlay. In recent years, multiple freeze-dryers have been introduced to the market, providing the most modernised software that minimises the total duration of the process as much as possible and with smart solutions that adjust the whole process to the particular products inserted into the machine.
How long does freeze-drying take?
The estimated freeze-drying time for an average portion is around 24 hours, but with the latest software, it is possible to freeze-dry a portion in as little as 13 hours. Warm and humid conditions increase drying time. After loading the home freeze-dryer and pressing the ‘Start’ button, the unit goes through a brief menu. Choose whether the food being inserted is already frozen (or not) and whether it is a solid or liquid product. The freeze-dryer then displays a message asking the user to close the drain valve and start the cycle.
The new software is smart. How do you make freeze-dried food yourself? Invest in good quality equipment. The key differences between the old and new software are as follows:
- It measures the freezing temperature.
- The vacuum pump is used as part of the freezing process. This is relevant because food cools more quickly.
- When the food is sufficiently frozen, it proceeds to drying rather than waiting for the full freezing time to complete.
- During the drying phase, the temperature rises to the specified storage temperature. This helps to achieve a better end product.
The greatest benefits occur when pre-frozen food is placed in it. However, reducing the processing time for food that is not pre-frozen is still possible.
Lyophilised and dried foods – which is better?
In terms of shelf life, lyophilisation is superior to dehydration. More moisture is removed in this process, so dried food can last for years or even decades when stored properly. A broader range of food items can be freeze-dried and usually retain better quality than dried food. Nevertheless, dehydration is more cost-effective and uncomplicated, making it a preferred choice for those with limited finances.