Advanced Food Processing Technology
Since ancient times, mankind has searched for the best way to preserve food so that it can last longer. To date, mankind's requirement for food preservation has gone beyond freshness to focus more on taste, nutrients and convenience.
Guided by a spirit of 'pursuing perfection', eLEAD and E.Excel are dedicated to finding the best ways to manufacture and preserve food — ensuring nutrients stay intact throughout the process. Join us as we explore our manufacturing processes and see how we use cutting‑edge technology to preserve plant nutrition.
Freeze-Drying
Research findings show that freeze-drying effectively preserves the freshness, nutrients, and quality of food. Plant foods processed through freeze-drying are able to retain the nutrients found in fresh plants in nature.
Water exists in three states: as a solid (ice), liquid or gas (vapor).
During freeze-drying, plant foods are flash frozen before being placed in a vacuum chamber where the ice is converted directly to vapor.
Step 1: Wash, Filter and Concentrate
This is the pretreatment stage for freeze-drying. First, the plant foods are washed thoroughly. If necessary, they are filtered or concentrated.
Step 2: Freeze
Prefreezing the plant foods is necessary during the freeze-drying process.
Technical Challenges:
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Strict Control of Prefreezing Temperatures (Usually from -50°C to -80°C)
If the prefreezing temperature is not low enough, the plant foods will not be frozen completely and this will compromise the subsequent process. If the prefreezing temperature is too low, it may damage the plant foods and cause unnecessary energy waste. -
Ability to Rapidly Lower Temperature to the Required Temperature
Take a home refrigerator for example. The temperature of plant foods placed in its freezer compartment drops gradually during the freezing process. Water in the plant foods forms crystals that burst the plant cells, causing the plant foods to become translucent and mushy. Hence it is vital to rapidly lower the temperature to protect the plant cells.
Hence, during the freeze-drying process, engineers meticulously calculate and control the duration and temperature required for freezing each kind of plant food to ensure accuracy.
Step 3: Dry
In a vacuum chamber with a fixed temperature, the ice in the frozen plant foods is converted directly to vapor to remove moisture.
Technical Challenge:
It is vital to ensure that the freeze-drying chamber is under vacuum and maintain the desired pressure and temperature. The slightest variation may cause an air leak and consequently damage the plant foods, resulting in an air-dried appearance: shriveled, collapsed and dark.
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Primary drying: Fixing the temperature at a certain value can evaporate about 95% of the moisture content in plant foods.
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Secondary drying: Dried plant foods typically have about 6% moisture content. E. Excel seeks to provide only the best by proceeding with secondary drying. It increases the temperature very slightly after primary drying to evaporate the remaining moisture.
After two stages of drying, the freeze-drying process is completed. Freeze-dried plant foods have about 1% to 4% moisture.
Freeze-drying requires strict controls every step of the way. The temperature and pressure in the drying chamber have to be maintained at a constant. Freeze-drying is difficult as it is a time- and energy-consuming process. For example, it takes three to four days to freeze-dry a strawberry; freeze-drying sliced strawberries requires 14 to 16 hours.
Advantages of Freeze-drying
Freeze-drying is the gentlest method of processing plant foods.
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Retains nutritional content
Most nutrients in the plant foods are retained as the plant foods are flash frozen and the ice is evaporated in a vacuum at very low temperatures during freeze-drying. -
Retains original flavor
Low temperatures ensure the sugar in plant foods is not burnt and help retain the natural flavors and aromas of plant foods in the finished product. -
Retains original shape, color and texture
There is no shrinkage after freeze-drying. A freeze-dried strawberry is almost the same as a fresh strawberry in terms of shape and size. -
Quick and complete reconstitution after adding water
If you look at a completely freeze-dried plant food under microscope, it has a honeycomb-like appearance. After releasing moisture, plant cells retain nutritious fiber and solid substances. In this way, their shape is maintained and freeze-dried plant foods can quickly reconstitute after absorbing moisture. Note that freeze-dried plant foods that are exposed to air absorb moisture easily. Hence they have to be stored properly in air-tight packaging. -
Long shelf life with storage at ambient temperatures without preservatives
Preservatives and additives are not needed due to the pure and natural processing and concentration methods. -
No costly refrigeration
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Light weight for easy handling and lower transportation costs
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More concentrated products
Spray-Drying
While freeze-drying is the best method for concentrating and preserving plants that lose nutrients in high temperatures, spray-drying is ideal for plants that require certain temperatures to eliminate toxicity. Soy is an example. Its concentration process requires a certain temperature to remove trypsin inhibitors, which inhibit digestion and breakdown of proteins.
In spray-drying, a substance is transformed from liquid to powder through a continuous method of spraying, blending and drying. It does not use very high temperatures, effectively preserving the taste, color and nutrients of a product.
Spray-drying uses machinery to atomize the raw material liquid into tiny droplets and expose them to hot air, instantly removing moisture to obtain powder.
Step 1: Concentrate and Atomize
Firstly, an ingredient is concentrated and atomized. The concentrated raw ingredient is fed to an atomizer, which uses a high-speed, rotating wheel to atomize the ingredient into tiny droplets.
A: The ingredient is atomized into tiny droplets
B: Hot air evaporates liquid
C: Dried particles settle at the bottom
Technical Challenges:
As the nozzle for spray-drying is only 100-200um wide, there are strict requirements for raw ingredients:
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If the ingredient concentrate is solely liquid, its nutrients will evaporate with moisture in the drying process later, and a powder cannot be obtained.
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If the ingredient concentrate is high in plant fiber, it may clog the nozzle, resulting in powder particles that are not homogeneous.
Hence, maltodextrin is added to ingredient concentrates to obtain homogeneous, fine powder. Maltodextrin is a colorless and odorless natural substance that is soluble in water.
Step 2: Dry
This step is completed in a drying chamber with controlled temperature and air flow. The drying chamber is usually a few stories tall. The raw ingredient is sprayed from the atomizer at the top. Hot air in the middle evaporates liquid, while dried particles settle at the bottom of the chamber. To ensure that the end product is of high quality, droplets must be in contact with heated air for just the right amount of time. Conditions in the drying chamber must also be carefully controlled, as factors such as the size of the chamber and air flow pattern can affect nutritional content of the final product.
Step 3: Separate
Using a separator, the powder is removed from the air stream and collected in a container. The product is ready to be packaged or combined with other ingredients.
Advantages of Spray-drying
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Through atomizing, spray-drying converts raw ingredients into fine particles. This increases surface area for evaporation such that drying is instant, resulting in perfect retention of the raw ingredient's nutritional value and taste.
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Powder obtained through drying is fine and dissolves quickly in water. It is frequently used for powder products. Spray-drying produces finer powder, which may result in static electricity during packaging. Hence, manufacturers often perform agglomeration to increase powder particle size for easier packaging.
Other Uses of Spray-drying
Spray-drying is usually used to remove moisture from raw materials. Other uses of spray-drying include creation of specific particle characteristics such as size, shape or density, and integration of additives. Spray-drying has the ability to create end products with exacting standards of quality. Hence, it is often the final processing step.