So i just got braces and i'm wondering about what something is in my mouth when i brush?

I spend 2-4 minutes brushing my teeth with an electrical oral b toothbrush, and then i floss, and then i use the crest pro health mouthwash they gave me. now, after i mouthwash and rinse, theres always a little bit of this white gooey substance on the front wire. is that food from the back that i did not get while brushing? or what is it?