During the microwave drying process, tofu skin may experience bubbling. The core principle is that microwave internal heating causes the moisture inside the tofu skin to vaporize rapidly, trapping the steam inside the protein skin and causing it to expand under pressure. Next, let's carefully analyze the reason.
Firstly, microwave heats up synchronously from the inside out, which is different from hot air drying from the outside:
1. Tofu skin has a high overall moisture content (>35%): A large amount of free water instantly turns into high-temperature steam in the microwave field, causing the volume to skyrocket in a short period of time. The surface of the tofu skin is first dried to form a closed hard film, and if the steam cannot be discharged, it will burst the skin layer and cause bulges and bubbles.
2. Uneven dryness and wetness, localized water accumulation: There is excessive water accumulation at the edges, corners, and folds of the soybean skin, causing localized water to concentrate and heat up, leading to rapid vaporization at a single point and the formation of localized bulges.
3. External dry and internal wet sandwich green body: In the early pre drying stage, only the skin is dried, and the moisture in the core is retained. After entering the microwave, the internal moisture breaks through the dry skin and bulges.
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