How does baking soda works as an desiccant? The thing is that I did a project from a website which is about the science of mummification and I can't find a way to explain the process of desiccation of the hot dog with the baking soda. 

By this I mean to answer questions like: Does the baking soda absorb or adsorb water? If it adsorbs then which type of adsorption is it? What's happening in details between the hot dog and the surrounding baking soda?

Here is the link to the project

My results did show a decrease in mass and size which is explained in the lost of water from the hot dog but how?
Frankly speaking, dehydration occurs because of osmosis. In fact, cellophane is used for "peel-before eating" hot dogs and also for osmosis experiments. Natural sausage casing (from intestinal submucosa) are also semipermeable membranes.
You might try an experiment demonstrating dialysis using sausage casing: in a cellophane tube, put plain tap (or distilled) water and tie the ends of the tubing. Weigh the watery "weiner". Immerse the tube in a concentrated solution of baking soda for a day or so, then weigh the sausage again -- some of the water should have leaked out into the outer solution, faster than larger sodium and carbonate ions can infiltrate, so the sausage should shrink.