I observe lots of bubbles on the noodle surface after frying. What causes this and how can I control it?
Deep frying noodles is likely to create bubbles, depending on exactly how the dough was formed; this is normal and expected. You see this on almost all battered fried foods.
The actual mechanism is that the heat of the oil partially sets the starches on the surface of the noodle fairly quickly, creating an a barrier to the further escape of water or steam. As the water under the surface converts to steam from the heat of frying, it expands dramatically (about 1,700 times the volume of the water), but has no where to go. The pressure created from the steam pushes out the surface noodle, creating a bubble.
As the frying continues, the starches completely set, making the bubble surface crispy and brittle.
I don't think there is a simple method to control this process. You could try frying at a slightly lower temperature, which would slow the process down, and perhaps allow more steam to escape rather than create bubbles, but I haven't tried this, and am not confident that it would work.