If the food is monolayer water (Aw 0.05-0.2, moisture content 3-5%), it can protect the internal substances from oxidation, which is represented by dried food. If the water content is lower than this, the change in food quality is mainly the oxidation of oil and the change of pigment. If the water content is higher than this, the change in quality is dominated by the hydrolysis of enzymes or non-enzymes and the microbial action.
The water content of the monolayer is the optimum water content for the storage and preservation of dehydrated foods.
Taiwan’s national standard stipulates that imported tea has a moisture content of 7%. Usually, green tea has a moisture content of about 4%, the water activity of 0.26 which is similar to that of milk powder. When the water activity is 0.3, the lipid oxidation rate is the slowest, so that tea is not dried as much as possible. The moisture content of the tea is set to 3-5%, which is just taking advantages of both the single molecular water layer and the lowest lipid oxidation.
Translated and edited by Adm./Fong Mong Tea Corp, all rights reserved.
Source from: TRES