What is the substance produced by iodine plus vitamin C reaction? Why is there foam after shaking?

Iodine in iodine solution is strongly oxidizing, while vitamin C is reducing, and they can undergo redox reaction.

The chemical equation is as follows: C6H8O6 (vitamin C, ascorbic acid) +I2=C6H6O6 (dehydroascorbic acid) +2HI.

Note: in organic reactions, organic compounds should be written in simple structures, and molecular formulas are used instead here.