try this one out..

to avoid the bitter edge that comes with some smoothies like banana..
pulse the switch and carefully watch the vortex. if it starts suck'n down oxygen and forms,the smoothy will be bitter..

for super smooth smoothy success, break the bananas into chunks and then fill 3/4 of the jug or less with water. then pulse, ensuring no vortex forms..

pour
then have some more!