WHAT IS FREEZE-DRYING?
We produce in our state-of-the-art facility via employing a unique and innovative technology which is called freeze-drying. Fundamental principles in freeze-drying comes from the sublimation process. Sublimation is a phase transition process from a solid to a gas without ever entering an intermediate liquid phase.
In our freeze dryers, moisture is removed from the product up to 98% under low vacuum and low temperature. Vacuum environment that is created by our freeze dryers to lower the air pressure in their chambers and initiates the phase change of water from ice crystals to gaseous without melting which has a significant impact to prevent the mushy and shrivelled appearance in finished products. That is why freeze-dried products still looks like a fresh product, instead of a mushy shape. Since vacuum makes sublimation possible under low temperature, freeze-dried products preserve its shape, aroma, flavour, colour, vitamin retention and nutrient content. Thus, freeze-drying is known as the best drying technique for heat-sensitive foods.
Freeze-drying is also knowns as lyophilisation which was invented in 1906. In the early stages, it was implemented to preserve blood serum due to ability of preserving of heat-sensitive biological materials.In the mid-1900s, beside pharmaceutical industry, it was started to use for foods. Freeze-dried foods became a major meal for astronauts and military rations. Currently, freeze-dried foods used for instant coffees, cereals, granolas, instant soups, ready to eat meals, natural food flavouring and colouring, backpacking meals, pet foods and standalone snacks.
Freeze-dried foods do not need to contain additives for preservation as their water activity level is around 0,2 where bacteria never grow.
Freeze-dried product, often considered the closest to fresh product, retains most of its nutrition.
SAME AS FRESH FORM
The process also preserves the actual colour and shape of the original raw material, reassuring consumers they are getting real fruits and vegetables in their diets.
LONG SHELF LIFE
Freeze-dried foods can last up to 20 years in the proper packaging and storage condition due to their low moisture (3%) content without any additives or preservatives.
Unchanged cell structure make them ready to take on water again. Freeze-dried products may rehydrate in a couple minutes and they can be used as a ready-to-eat meals.
Freeze-drying removes about 97% of a food’s water content and so the weight of that food is reduced by as much as 90%. Light freeze-dried foods are very handy and convenient for traveling and long-haul endurance events.
As they have crispier texture, they are strong alternative to unhealthy crunchy snacks. Moreover, this texture increases the fruit and vegetable consumption for kids.
WHAT IS CONVENTIONAL DRYING?
Conventional, also known as air drying process is a method that the hot air (almost 70 °C) is used to evaporate water out of the product that needs to be dried.
DIFFERENCE BETWEEN CONVENTIONAL AND FREEZE DRYING
Requires a fair amount of preservatives to keep them fresh.
No need to add in additives to preserve the food due to very low moisture ratio.
Lose nutritional content due to the use of heat in the processes.
Retains 97% of its original nutrition.
The heating process destroys flavor, shape and colour.
Low heating and freezing process preserves flavor, shape and colour.
Higher moisture content extends shelf life up to 2 years.
Very low moisture content extends shelf life up to 20 years.
Tends to be chewy and hard on the outside because it still retains much of its water content.
|Requires a fair amount of preservatives to keep them fresh.
|No need to add in additives to preserve the food due to very low moisture ratio.
|Lose nutritional content due to the use of heat in the processes.
|Retains 97% of its original nutrition.
|The heating process destroys flavor, shape and colour.
|Low heating and freezing process preserves flavor, shape and colour.
|Higher moisture content extends shelf life up to 2 years.
|Very low moisture content extends shelf life up to 20 years.
|Tends to be chewy and hard on the outside because it still retains much of its water content.
FREQUENTLY ASKED QUESTIONS ABOUT FREEZE DRYING
Freeze-drying is the most advanced dehydration technology. Iced molecules inside the frozen foods are removed by sublimation (transition directly from solid to gas state) under low pressure and low temperature.
Lyophilization is the synonym of freeze-drying which is usually used in the academy and pharmaceutical industry.
Fundamental principle in freeze-drying comes from the sublimation process into the specialized machines, under thousandth of atmospheric pressure. Sublimation is a phase transition process from a solid to a gas without ever entering an intermediate liquid phase. Frozen products enter the process and start drying about 24 hours under 40°C temperature.
Conventional drying, also known as the air-drying process is a method evaporating water out of the fruit by using hot air (~70 °C) to be dried. As a result of hot air circulation, the loss in nutritional value, vitamin and original quality are much more than freeze-drying. Freeze-dried fruits preserve their shape, aroma, flavor, color, vitamin retention, and nutrient content. Thus, freeze-drying is known as the best drying technique for heat-sensitive foods. Apart from loss in nutritional values and original features, air-dried foods cannot stay as long as freeze-dried foods without additives due to containing a higher level of moisture. For more details, please see the comparison chart of the two methods above.
As an outcome of the fundamental principle of freeze-drying, products can retain their nutritional values, original features, and their shelf life without any added sugar or preservatives. There is almost no difference between fresh and freeze-dried fruits in terms of health. Moreover, they are controlled by global quality norms which cover pest and microbiological analysis. That process makes freeze-dried fruits safer than fresh ones.
Freeze-dried fruits do not need preservatives to retain their shelf life as they have a low moisture ratio (~3%) where moulds, yeasts, and bacteria cannot grow. Namely, there is no water and no microbiological life that leads to spoilage. Additionally, they can preserve their fresh taste because of dehydration under low temperatures (~40°C) without added sugar or sweetener.
As a result of low moisture and water activity value, their lifetime is calculated as approximately 20 years in academic research. However, the expiration date is regulated by the government’s food institution.
Worsening of foods occurs as a result of a microbiological activity which is evaluated by water activity (AW). If AW is below 0,8 bacteria, if it is below 0,6 yeasts and moulds cannot live. 0,6 is a safe level to guarantee the safety of storing dried fruits. Freeze-dried fruits’ AW value is around 0,2 where almost water and microbiological activity cannot be observed. The low value of AW prevents freeze-dried fruits’ shelf life without preservatives.
The process of freeze-drying solely removes fruits’ water. Fibre, vitamin, and antioxidant contents stay in fruits. And freeze-dried fruits just lose 3% of nutritional value compared to fresh fruits in this process. But this comparison is made at the time of harvesting. In our daily life, harvested fruits spend days in storage, transportation, stores, and refrigerator. Within this time, they continue losing nutritional value and others. For this reason, freeze-dried fruits that are produced in a short time after harvesting should have higher nutritional value than fresh.
On average, the water content of ready-to-eat (peeled, pitted, etc.) fruits and vegetables are 86% and 90% respectively. Almost full of water can be removed from food and fruits’ weight drops to 1 in 7, and vegetables’ weight drops to 1 in 10.
Although it depends on the product’s shape, dimension, and cutting format, it takes between 20 and 48 hours.
Although freeze-dryers and freeze-drying processes are run under industrial production conditions, there are simplified freeze-dryer for home use in the market.