Today, many countries already use stevia in their daily lives. Stevia is native to Amambay and Iguacu on the border of Brazil and Paraguay. Stevia contains diterpene glycosides, stevioside, rebaudioside and dulcoside. Stevia powder is 150-280 times sweeter than sucrose.
Purpose of Drying
Stevia is dried to prevent contamination by mold, bacteria, and enzymes. Chemical changes can occur in stevias, such as hydrolysis, oxidation, isomerization, and polymerization. Additionally, dried stevia powder is easy to grind and transport.
Drying Methods
There are 3 ways to dry stevia: natural drying, oven drying, and freeze-drying.
There are also 2 ways of natural drying: drying in the sun and drying in the shade.
Dry In The Sun
The stevia is usually spread on slats high above the ground, both to avoid mixing with sandy soils and to allow the bottom of the stevia to aerate. Stir regularly during sun drying. Exposure time can vary from a few hours to a few days. Depends on the amount of water contained in stevia and the weather. This drying method is simple and cheap, but has some disadvantages, such as: subject to weather, dusty, attracting flies, etc. Some of the active ingredients in stevia can be altered by UV light.
Dry In The Shade
Spread sweetgrass thinly on slats, then hang or extrude it into an X shape on a wire rope. Dry in a tent with no surrounding walls.
Oven Drying
The temperature of the vacuum drying oven is adjustable, and the drying temperature can be changed between 30-800. In the beginning, the temperature should not be too high, as it will create a thin layer of hay, preventing the moisture inside from evaporating. Ventilation conditions (usually with exhaust fans) must also be monitored to be just enough to remove the steam-saturated air from the drying chamber.
Oven drying trays are typically 1.5m long and about 0.80m wide and are made of metal mesh or fabric. Trays are stacked on top of each other. There is enough space in the middle for air circulation.
Freeze Drying
Stevia cools rapidly at very low temperatures (-800°C). Allow the water inside the material to crystallize quickly in the form of small crystals and make sure they stay cool during the freeze-drying process, placed in a sealed chamber connected to a vacuum freeze dryer. The solid water in the material sublimates at very low pressure (10-5 mmHg).
With freeze-drying, the raw materials can be completely dried and the non-volatile active ingredients can be well preserved. The enzyme is inhibited but can function again under normal conditions, the tissue structure is not changed. After drying, the moisture content of stevia reaches 10-12%, with no impurities, and no additives.