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| The benefits of Freeze-dried foods |
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Top Benefits of Freeze Drying
In contrast to traditional dehydration, the unique freeze-drying technique completely removes all moisture while generally having less of an impact on food flavor. Food is frozen and put in a powerful vacuum during the freeze-drying process. The food's water sublimates, turning instantly from ice to vapor.
The process is most frequently used for instant coffee but produces excellent results with fruits like apples.
Freeze-drying, called lyophilization or cryodesiccation, is a dehydration technique frequently used to preserve or make perishable materials more portable.
The term "Lyophilization," which means "to make solvent loving" in Greek, is the other word for freeze drying chosen by the pharmaceutical industry.
The freeze-drying process:
- begins with the substance being frozen,
- followed by a drop in atmospheric pressure,
- and the introduction of sufficient heat to allow the substance's frozen water to transfer directly from the solid state to the gas state.
The three stages of the drying process
In industrial applications, the entire drying process consists of the following 3 stages:
Freezing
The substance is frozen during the freezing process.
This is accomplished in a laboratory by putting the substance in a flask designed for freeze-drying and spinning the flask in a shell freezer bath that is chilled by:
- mechanical refrigeration,
- dry ice,
- methanol,
- or liquid nitrogen.
A freeze-drying machine is often used to freeze on a greater scale.
The substance must be chilled below the lowest temperature at which its solid and liquid phases may coexist in this stage. This guarantees that the next phase will use sublimation rather than melting.
Larger crystals are simpler to freeze-dry.
The product should be frozen gradually, or subjected to temperature cycles, to yield bigger crystals.
Annealing is the term for this cyclic process.
Large ice crystals, however, will shatter the food's individual cells' walls. The freezing range is typically between -50°C and -80°C.
The freezing phase is the most crucial in the freeze-drying process because the product might be ruined if done incorrectly. It takes several months for large things to freeze dry.
Initial Drying
The pressure is reduced (to a few millibars or less), and the material is heated enough for the water to sublimate during the initial drying phase.
The latent heat of the sublimation of the molecules that are sublimating can be used to determine how much heat is required. Around 95% of the water in the material is sublimated during this first drying phase.
In the industry, this phase can take several days, and if too much heat is applied, the object's structure may change.
Pressure is managed during this stage by using a partial vacuum. Sublimation may be used as a purposeful drying technique since the vacuum speeds the process.
In addition, a cold condenser chamber and/or condenser plates offer a surface for resolving the water vapor.
This condenser does not contribute to the preservation of the material's frozen state and keeps water vapor from entering the vacuum pump, where it can harm the pump's operation. Usually, the condenser's temperature is below -50°C (-60°F).
Secondary drying
The initial drying phase removes the ice; thus, the secondary drying stage aims to eliminate unfrozen water molecules.
The material's adsorption isotherms control this stage of the freeze-drying procedure. To disrupt any physicochemical contacts that have developed between the water molecules and the frozen substance, the temperature is raised in this phase above that in the initial drying phase and may even rise above 0°C.
To promote desorption, the pressure is frequently reduced at this stage. Some products, nevertheless, gain from increased pressure.
An inert gas, such as nitrogen, often breaks the vacuum once the freeze-drying process has been completed before the material is sealed.
The final residual water content in the product is quite low after the process.
Freeze Drying Advantages:
The following is a list of the top benefits of freeze-drying:
- The heat-sensitive material is not damaged too much.
- The creation of porous, spongy structures.
- Rehydration's speed and completeness.
- The ability to sterile-filtering liquids immediately before dispensing.
- The product may be kept at room temperature without refrigeration for a long time without becoming bad. By significantly lowering the water content, it prevents the activity of enzymes and bacteria that would typically spoil or degrade the product.
- The material being dried by freeze-drying often does not shrink or become more durable.
- The method is useful for food preservation since the aromas, fragrances, and nutritional value often stays unaffected.
- Free-drying is beneficial when a product satisfies one or more of the following conditions.
- It's unsteady.
- It is heat stable.
- Complete and quick rehydration is necessary.
- A high-quality product
- Weight reduction is necessary, and
- Storage in a cold or frozen state is inappropriate.
Drawbacks of Freeze Drying
The following are the main drawbacks:
- High equipment capital costs
- High cost of energy
- A long processing time (typically 4-10 hrs. per drying cycle)
- Potential product harm from pH and tonicity fluctuations.
Are frozen foods nutritious?
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| Freeze-dried fruits |
Freeze-dried foods are a healthy choice. With so many benefits, freeze-drying is one of the most used dehydration techniques.
Free-drying is one of the finest methods for retaining the action of healthy plant compounds, such as phytochemicals and minerals, while keeping color, taste, and structure. Because of this, it is frequently utilized to make high-quality food products.
According to research, freeze-drying, as opposed to other drying techniques, is particularly good in preserving antioxidants such as anthocyanins, flavonoids, ascorbic acid, and vitamin C.
Antioxidants are beneficial compounds that support your body's defenses against the negative consequences of oxidative stress. These compounds also provide most fruits and vegetables with their medical benefits.
The contrary may also be true, depending on the fruit, even if freeze-drying can occasionally even boost a fruit's phytochemical content.
Also, by lowering a product's water content, freeze-drying aids in extending a food's shelf life since lower water activity prevents the growth of most bacteria, yeasts, and molds. This is crucial for fresh plant-based meals, which might not always be accessible.
Last but not least, lowering a product's water content results in a smaller, lighter product that is easier to handle, transport, and store.
Suitable foods for freeze-drying
Foods that have been freeze-dried are often used for:
- military rations,
- space exploration,
- hiking,
- camping,
- and other outdoor activities.
They are chosen over traditional foods because they are light, have a long shelf life, are portable, and are simple to prepare.
While most freeze-dried meals are made from plants, this technique may be used to preserve various foods.
Some foods that can be freeze-dried are listed below:
- Fruits: Fruits like strawberries, apples, durians, blackberries, bananas, pears, oranges can be freeze-dried.
- Vegetables: Almost all vegetables, such as carrots, asparagus, mushrooms, peppers, pumpkin, and tomatoes, are suitable.
- Meats: Beef, fish, chicken, eggs, pork, turkey, and shrimp are usually freeze-dried.
- Grains: Rice, beans, pasta, quinoa, and polenta are suited for freeze-drying.
- Frozen meals: Thai snacks like Thai rice and Thai noodles and whole meals like Pad Thai, stews, and chili are often freeze-dried for transportation.
- Beverages: Milk, juices, coffee, and tea for instant drinks are subjected to freeze-drying too.
- Spices: Ginger, oregano, mint, basil, and garlic
- Sweeteners: Maple syrup for sugar powder is freeze-dried for a longer shelf life.
Conclusion:
Frozen food is dehydrated by freeze drying, often called sublimation, which transforms ice into vapor. It is a healthy method of food preservation since it maintains the food's color, flavor, and appearance, as well as the majority of its nutrients and healthful plant compounds.
It does not, however, eradicate dangerous microorganisms. Fresh foods must thus be cooked before being freeze-dried. If you don't have a home freeze-drying machine, you may freeze-dry your food at home using your freezer.
Author: Nancie Mathews is a digital marketing manager at Zane Thai Products. She has six years of experience as a content writer in different marketing firms. She likes to write on health and food-related topics.