Several factors can contribute to a cucumber salad's astringent flavor.
Cucumbers that are overripe have the potential to become sour. Cucumbers should be firm and vibrant green in color. Soft or yellowing cucumbers should be avoided.
Cucurbitacin, a naturally occurring bitter substance in some cucumbers, can have a bitter flavor. This occurs more frequently in cucumbers that have been stressed or subjected to environmental elements like heat or drought.
Not removing the seeds: Before creating a salad, cucumber seeds should be removed because they can be bitter as well. To do this, cut the cucumber in half crosswise, then use a spoon to scrape out the seeds.
A salad can taste bitter if there is too much salt added, so sample the salad as you go and adjust the seasoning as necessary.
Use fresh, firm cucumbers, remove the seeds, and sample the salad as you go to make sure the seasoning is balanced to prevent a bitter cucumber salad.