Is rubbing cucumbers an old wives tale?

I grew up in India and every time we cut cucumbers we had to cut off the ends and sprinkle it with salt and rub it. It brought out a white sticky sap. You are supposed to cut that off and rinse the cucumber. Voila the bitterness is gone!

Like many other things I attributed this to an old wives tale, until in 2 separate classes, 2 different students mentioned doing the same in Mexico. It got me wondering that it would be highly coincidental to have completely unrelated cultures follow the same practice. Of course on asking them I got the expected response that they were following what their grandmother did without knowing the reason.

I started doing some research, and lo and behold there is a reason. Cucumbers are members of the gourd family which produces a particular class of compounds called CUCURBITACINS which are bitter. These compounds are produced as a self-defense mechanism to protect themselves from being eaten. The compound tends to be concentrated at the ends. Hence you rub the ends, sprinkling the salt helps in extracting the white milky fluid that contains the cucurbitacins. By cutting off the ends of the cucumber you reduce the likelihood of getting the cucurbitacins to spread to the rest of the cucumber. Some say if you don’t cut off the end the bitterness gets rubbed back in.

Next question that came to mind was why some cucumbers are bitter and some not?

A couple of things determine the amount of bitterness in a cucumber. Another enzyme called elaterase hydrolyses to non-bitter compounds. Depending on environmental conditions the enzyme will vary with different varieties. Also if the cucumber grows with less water it tends to be more bitter. The bitter compounds are much less prevalent in the bred varieties compared to wild cucumbers. This makes sense because my cucumbers in the US are almost never bitter when bought at stores, but I have experienced bitterness in cucumbers from the farmers market.

Are cucurbitacins safe to eat and nontoxic?

Yes just not very appetizing.

This makes me wonder about all the different traditions that we follow and pass it off as superstition or habit. I am sure there is a science to most.

Does your culture have any?