What are freeze dryers?
Producing freeze-dried products is an added value in addition to being able to quickly make your investment profitable if you already use these products regularly.
You will be able to produce unique, local and market products, taking advantage of the best season to buy them and make the most of the organoleptic properties of a unique product.
You can produce different ingredients and elaborations such as fruit skewers, powders, crispy slices, spices, flowers, PoP Candy, etc. Bringing unique and surprising elements to your menu.
Which freeze dryer should I buy?
Choosing a freeze dryer is not a simple decision, as there are many options on the market.
The most obvious considerations are price, system, quantity to be produced, technical service.
Price is a main concern when buying a freeze dryer: these devices are very expensive and it is normal to think twice before the purchase.
The system is an essential consideration when buying a freeze dryer, and this is why after exploring different options, we have selected our LyoChefs. Choosing a freeze dryer where the product is inside the same cold trap is essential, the energy and time saving is remarkable.
For the rest of the features, it is not necessary to have very precise freeze dryers. We must remember that we are often processing low-cost products, not vaccines or products of very high value, which require equipment that works at very low temperatures, the simplest ones reaching -50°C or -60°C. Such refrigeration equipment is very expensive. The vacuum pump also does not need to have a very high vacuum. With a high vacuum oil pump we can freeze-dry any food without any problem. After all, from our expertise, choosing LyoChef freeze dryers is the most convenient choice for a restaurant, bakery, catering or cocktail bar.
It is also important to point that the Harvest European technical service, centralized in Barcelona with all kind of services and spare parts for your LyoChef freeze dryer.
LyoChef has an unbeatable price compared to all other options. And the best thing about it is the production of 1400 kilos per year.
What types of vacuum pumps can we use?
There is a big difference between the two types of vacuum pumps that are available, and their price must be taken into account.
The “Harvest” high vacuum pump is equipped with a piston system lubricated with long-life synthetic oil. This type of pump with this oil requires cleaning and water separation every 3-4 cycles. We remind you that despite the cold trap, part of the steam that is released from the food is absorbed by the pump itself, being trapped in the oil. The pump itself has a decanter that helps to separate this water. A complete oil change is also necessary after about 25 uses.
The Oil-Free High Vacuum pump is actually much more expensive than the first one, but it is really the best option for those professionals who do not want to worry about continuous maintenance. The pump is a rotating piston that evaporates the steam absorbed in the process. No maintenance, higher performance and long-time efficiency.
What is freeze-drying?
Freeze-drying is a food preservation technology based on drying food by the process of sublimation of the moisture it contains.
What is sublimation?
To explain the concept, we will start by focusing on what sublimation means. When we freeze the product, the aqueous part freezes, and thanks to this technology, we remove the ice by applying small pulses of heat under vacuum conditions. In this way, we prevent the water contained in the food from returning to its liquid phase, as its steam is trapped by the vacuum and frozen in the cold trap. In short, sublimation involves moving a product from the solid to the gaseous state without passing through the liquid state.
The process takes between 16 and 24 hours, depending on the size of the product. Through vacuum dehydration, the food loses more than 90% of its original weight. Moisture is reduced to at least 2%, which disables any action of micro-organisms and enzymes.
In addition, this combination of freezing, vacuum evaporation and drying allows all the watery content to be removed, leaving the concentrated flavour inside the freeze-dried food, making it an explosion of taste in the mouth.
Its texture is crunchy but earthy, i.e., it crumbles when bitten and merges with the moisture of the saliva, leaving the whole mouth with an intense and lingering taste. In gastronomy, freeze-dried products add a special value to many dishes and are used in nitro cooking as “dragon” elements with a vapour effect.
Origins and evolution of freeze drying
The freeze-drying process, or a similar natural process, originated in the Inca Empire, located in the Andean highlands at an altitude of 4000 metres. In this region, the settlers produced a product known as “Chuño”, which consisted of Andean potatoes, a tradition that is still used today.
The technique involved leaving the harvested potatoes on the ground to freeze overnight due to low temperatures, while during the day, the combination of sunlight and dry wind provided the ideal conditions for the changes of state to occur. Water went directly from solid to gaseous state, without passing through a liquid phase. It is relevant to mention that, at this altitude, the atmospheric pressure is significantly reduced, reaching, for example, 616 Mb, creating conditions that resemble being slightly in a vacuum.
This basic procedure was refined by industry, integrating concepts such as vacuum, freezing and dehydration. In the food industry, freeze-drying was initially employed in the production of special foods for climbers, astronauts, military bases and other similar purposes. Over time, freeze-dried products have transcended their industrial use to reach the general consumer, thus expanding the market for these high value-added products and gaining recognition in gastronomy, where renowned chefs interact with this technology to create their own unique products.
It is crucial to remember that freeze-drying can extract more than 95% of the water from food, generating significant benefits in terms of transport costs by allowing more goods to be loaded without relying on the cold chain (as the products are microbiologically stable). At the end of the process, the food acquires a rigid structure, retaining its shape and volume, but reducing its weight, keeping its nutritional and organoleptic properties intact.
Rehydration restores the food’s original texture, aroma and flavour.
What is a freeze dryer?
A freeze dryer is an automated device designed to carry out the freeze drying process. These devices vary according to the product to be freeze-dried, the quantity, the cost and the system used. They are mainly classified into models intended for laboratories, universities, scientific studies, and also those used in the culinary field. On the other hand, there are freeze dryers that are designed for large-scale production, which can be of considerable dimensions and allow the storage of trolleys inside a main chamber.
As for the smaller models, intended for laboratory and scientific use, these are complex and delicate tools, designed with control systems and parameterisation for precise handling. However, maintenance can be a challenge. High-cost freeze dryers offer highly accurate performance, but their price makes them unfeasible for gastronomic use.
An example of a more affordable and practical freeze dryer is the Lyo Chef family. This device has a system that freezes thanks to a powerful cooling unit, which then acts as a steam trap, freezing it to -40º before it reaches the pump. Its construction is completely systematised, allowing the user, once each process has been parameterised, to simply freeze-dry a new batch every 24 hours.
Lyo Chef
Lyo Chef gastronomic freeze dryers have been designed for small batch freeze drying in culinary environments such as kitchens, pastry shops and cocktail bars. Their compact design, combined with powerful features and automated functions, makes them an ideal solution to meet the needs of any professional. This allows the creation of products that, due to their high quality or lack of market availability, may be difficult to access or produce cost-effectively on a recurring basis.
The models available from 100% Chef are the Lyo Chef – M and Lyo Chef – L, which offer different sizes and capacities to suit the specific needs of each user. This integrated freeze-drying system not only takes up very little space in the workshop, but is also characterized by its ease of operation, allowing anyone to operate the machine with a minimum of basic training.
How does the Lyo Chef freeze dryer work?
You put the fresh food into the trays, close and start the Lyo Chef. The first phase involves freezing both the chamber and the food. The powerful pump, like a blast chiller, reduces the temperature in the chamber to -40°C. At this point, a special high-vacuum pump is automatically activated.
During the entire process, you can monitor times, temperatures, and process status on the colour LCD display.
The next stage is freeze-drying. The trays begin to temper thanks to a thermal silicone in their support, causing a slight decrease in the temperature of the food. This reduction generates the evaporation necessary for the drying of the product. The steam released is trapped on the walls of the main chamber. This process is repeated throughout the course and accelerates the sublimation phase.
Once the preset time has been reached, the chamber is pressurized again and the trays with the food are removed, keeping them under maximum dryness conditions until they are ready to be served.
To start defrosting, set Lyo Chef to the corresponding position and open the exhaust valve. An internal heating element facilitates the rapid defrosting of the layer of ice formed around the chamber. Afterwards, the trays are thoroughly cleaned to start a new freeze-drying process.
For optimal performance, it is recommended to drain the oil from the vacuum pump every three cycles. This involves letting the oil stand, decanting any water not trapped by the cold trap, refilling the pump with clean oil and topping up to the average working level. Lyo Chef provides a decanter jug that facilitates this process, saving time and oil.
For a visual guide on how to work with Lyo Chef, we invite you to watch our videos in the “YOU COOK” section.
Which products are freeze-dried?
It is essential to understand which foods are suitable for the freeze-drying process. Careful preparation of the raw materials is crucial, as once freeze-drying is complete, these foods will not be manipulable. For example, freeze-drying fresh fruit skewers can result in a unique garnish for cocktails or desserts.
It is recommended to prepare foods in small portions, in layers, in small pieces or thinly sliced. This includes everything from sweets and small fruits such as raspberries, strawberries, blueberries, and blackberries to sliced mushrooms, truffles, seaweed, oysters, sea urchin, cooked shellfish, flowers, aromatic herbs, raw fish or seafood, mousses, cakes, yoghurt or ice cream. The results obtained with these small formats are surprising. They can be used to decorate and finish desserts or plates, as well as for fillings. In salads, dipped in oil (maintaining their crunchy texture), or as ingredients in savory dishes to provide an intense and crunchy texture.
Freeze-drying can also be applied to different products in order to obtain powders, used to strengthen sauces, or create exceptionally intense infusions in front of the customer, e.g., shrimp heads, mushrooms or less attractive trimmings. Also, to enhance chocolates, butters, meringues, or biscuits, adding flavour to drinks or serving as decoration in glasses.
All products with water in their structure are suitable for freeze-drying. It is important to note that products with high fat or alcohol content are the least suitable for freeze-drying.
Freeze-drying of frozen fruits can be a cost-effective option to ensure a consistent quality standard throughout the year.
How to freeze-dry?
If we want to make several products in the same batch: we must select by size, thickness, or amount of water. For example, we should not mix flowers or leaves with fruits with a high-water content, or pieces of a much larger size by weight. The times can be very different, for example, flowers can take 18 to 24 hours and half tomatoes between 24 and 36 hours depending on their size.
If the fruits have skin or are products with a lot of fibre (whole spring onions), it is better to prick them with a needle to help the extraction of water not only from the cut part. In the case of flowers, leaves, seaweed, etc., the products should be dry and drained before placing them on the tray.
Do not stack the products and try not to make overlapping layers. The product that is in contact with the tray will freeze-dry before the one on top and the freeze-drying will not be done correctly, and the products may remain stuck together and with humidity inside.
How to freeze-dry candies or confectionery?
One of the most fun techniques is to freeze-dry candies or sweet jellies. We call this technique POP CANDY. For this we will work with other parameters.
Cool the chamber to -17°C. Introduce the candies and heat the trays between 57 and 61°C, make a vacuum and leave for about 3 hours.
The result is surprising and unexpected. Not all candies behave the same depending on the amount of sugar and water inside. For example, gummy bears tend to suffocate a lot, as well as other candies like Snickers, we are still working on it and will soon be able to explain more in future posts.
How much does it cost to freeze-dry food?
The costs are very relative, depending on the cost that each one has when it comes to paying for electricity, timetables, tariffs etc. But after calculating the real costs of a 24 hour process, it is actually lower than we all think.
28 KW is a relatively affordable consumption. This consumption covers the cooling process of the tank, which we can reduce if we introduce previously frozen products or if it is a second freeze-drying process. In addition, this energy consumption covers the pump and the heating of the trays.
In Spain in 2023, where energy is on the rise, the cost for this process is around €4 per production. In this production we can produce between 3 and 7 kilos of fresh product. Once the calculation has been made, we will see that the cost of the products obtained is less than half of what we are paying, if we buy them from a local supplier. Moreover, we will obtain products of better quality, controlled origin and much more original ingredients or preparations with added value.
How many kilos can I freeze-dry in 24 hours?
Depending on the freeze dryer you choose, the production will be much higher. If we take the “Lyo Chef L” freeze dryers with 24-hour cycles as an example, the annual production will be around 1400 kilos per year. Not a negligible amount for a kitchen. The savings are very evident, and the machine can be profitable within a few months.
How can freeze-dried food be stored for a longer period?
The shelf life of freeze-dried foods can be extended by several years. During the freeze-drying process, the water content is removed, inhibiting the action of micro-organisms and enzymes. However, to ensure long-term preservation, it is essential to store them in an environment free of moisture and oxygen. It is also important to keep it away from sunlight. If we respect all these conditions, a freeze-dried ingredient can stay intact for years.
To do this, freeze-dried foods should be quickly placed in vacuum-tight containers or silica gel-sealed containers. Placing these containers in a dry cabinet such as DRY BOX further contributes to maintaining ideal conditions. We strongly recommend this option, as the effort and time invested in the process is enough to try to keep it in perfect conditions.
Another option is to use vacuum packaging in airtight containers and add bags of ferric antioxidant or “OXIGEN ABSORBER”.
It is crucial to note that a freeze-dried product that retains moisture or loses its crispness may lose some of its appeal and be prone to spoilage. Bacterial life can come into play under these conditions, highlighting the importance of preserving them properly to ensure their quality over time.
Producing freeze-dried products is an added value, which also helps you to get a quick return on your investment if you already use these products on a regular basis.
You will be able to produce unique, local and market products, taking advantage of the best season to buy them and making the most of the organoleptic properties of a unique product.
You can produce different products such as fruit skewers, powders, crispy slices, spices, flowers, PoP Candy, etc. Bringing genuine and surprising elements to your menu.
Do you want to attend free freeze-drying courses?
If you are interested in learning more about freeze-drying and becoming an expert in the use of LYOCHEF, sign up to our Mailing and we will notify you when free courses are available from our LAB.
