Why are cucumbers bitter
Although the cucumbers that we buy from the market or the cucumbers that some of us grow in our gardens are not that bitter, wild cucumbers are mostly very bitter. The bitterness in all cucumbers is due to the presence of an organic compound in them called cucurbitacin. Cucurbitacin is present in all cucumbers, but their concentration in the wild cucumbers is much greater. It is not a compound that is generally found within fruits of a plant as it is more a part of the stem and the leaves, but in some cases like the cucumber, it is found to be existent. However, the amount of cucurbitacin present, not only differs from one fruit species to another, it also varies from one cucumber to another.
Slicing a cucumber properly for consumption is necessary to avoid the bitterness. While slicing it, the first thing to do is to cut off the stem area and the next is to peel the outer skin cleanly and adequately. This is to be done because the green outer skin and the stem portion has the highest amount of cucurbitacin and thus are most bitter. Also, it is necessary that you wash the slicing knife with water in between cleaning it in the above mentioned way and actually slicing the fruit portion of the cucumber. This will ensure that you do not get the bitter organic compound on to the non-bitter edible part.
There are a few definite reasons that are discovered as being responsible for making the cucumber bitter and the most common cause is heat. If a cucumber plant is subjected to a lot of heat stress, then the cucumbers will have more cucurbitacin in them. Apart from heat, even heavy fluctuation of the temperature and climate from one extreme to another may increase the concentration of the compound in cucumbers. As I have stated earlier, stress is responsible for making cucumbers bitter, so even stress from excessive or lack of watering may result in bitter tasting cucumbers.
If you happen to grow cucumbers in your garden and you maintain all of the measures for producing non-bitter cucumbers, then you are probably going to produce cucumbers with very little bitterness in them. But if it is still bitter, then you need to change the seed source as that means that the seeds of your cucumber plant was from a plant that produced bitter cucumbers due to genetic reasons.