Cucurbitacin B and cucurbitacin C are the compounds which cause bitterness in cucumbers. The amount of bitterness cucumbers contain varies from year to year. There are many theories about bitterness but it has been difficult to obtain consistent information as to its cause. Some varieties are bitterer than others and the rule of thumb is, the smaller the cucumber, the less bitter it tends to be. To be on the safe side, I always tend to buy or grow Lebanese cucumbers.
This is a method I use to reduce bitterness in cucumbers. You may ask that how would you know whether a cucumber is bitter or not without tasting it. The short answer is, you can’t. So with all cucumbers, regardless, I prepare them using this method.
Before peeling the cucumber, cut a slice from the top of the cucumber (about 1.5 cm thick). Using this piece, rub vigorously, in a circular motion, on the top of the cucumber where the slice was cut from. You should see some foam appear. A thicker whiter foam indicates a slightly bitter cucumber. Slice off about ½ to 1 cm and discard and use the rest of the cucumber as desired. This should help remove some of the bitterness.