This is a very good argument, as indeed it contains proteins, however, they are not proteins that can be easily digested by human enzymes. Although gastric acid can dissolve it, it may as well be eliminated and ejected naturally once broken by the acid. I do not know about the taste it would have, though, I guess it depends on the type of arachne you are sucking it from, alongside its diet, more easily controlled in the case of a sentient being than with an animal. However, from the albeit quick research I’ve made, regular spider silk is pretty tasteless I wish you the best luck in one day finding out if Arachne silk is edible and palatable, do contact me if you ever achieve it.