Why is it inadvisable to store carbonated beverages, milk or dairy products, and fruit juices in a vacuum-insulated mug? There are two primary reasons. First, carbonated beverages contain dissolved gases that possess strong permeability. The leak-proof sealing rings inside vacuum-insulated mugs are typically made of plastic; when used to hold carbonated beverages, these seals are prone to leaking. Furthermore, under bumpy conditions-such as during transport-the gases within the carbonated beverages generate bubbles, which can exacerbate the leakage problem.
Second, carbonated beverages, milk, and dairy products all contain acidic components. These acidic substances can react chemically with the stainless steel interior of the mug, causing the beverage to spoil or acquire an altered taste. The degree of oxidation in the stainless steel is directly influenced by the quality of the steel used in the mug itself. High-quality stainless steel-such as Grade 304-exhibits minimal oxidation, whereas lower-quality grades-such as 202 and 201-are far more susceptible to oxidation.
Generally, the stainless steel materials used in vacuum-insulated mugs fall into three categories: 304, 202, and 201. Among these, Grade 304 is classified as food-grade stainless steel; it is more expensive, and manufacturers in China's Guangdong province frequently utilize this material. Conversely, Grades 202 and 201 are considered more ordinary and of lower quality; manufacturers in the Zhejiang region tend to use these materials more often.
In summary, acidic beverages-including carbonated drinks, milk and dairy products, and fruit juices-can lead to issues such as leakage, spoilage, and altered taste in vacuum-insulated mugs. Therefore, it is not recommended to use vacuum-insulated mugs to store these types of beverages.