Frothy Spit
If it's what I think it is, those are "the foamies" and they result from eating too large a mouthful and having your body try to send more saliva down the esophagus to help it move down. The best thing you can do is to either "urp it up" and get the excess out of the way, or try some papaya solution to help break it up.
Next time, chew it more, and eat slower and smaller bites.
