Does Rubbing Cucumbers Really Remove Bitterness? Find Out Here

The other day I had some friends over for dinner and a couple of them were chatting in the kitchen as I ambled around putting together a chicken curry. In my opinion, no curry is complete without a salad on the side, and true to Indian tradition, this meant the omnipresent plate of cucumber, raw onion and tomato.

Absentmindedly, I started chopping the vegetables and as I got to the cucumber, I heard a voice pipe up from behind, “Why the hell are you doing that to the cucumber?”. I looked down, wondering whether I was doing something strange, but no, I’d just done my regular move of taking off the cucumber end, salting it and scrubbing to remove the white foam. I explained that it was to remove the bitterness in the cucumber, and was met with some very confused looks. 

It got me thinking that even though this was something I’d been doing all my life, I had absolutely no idea why I did it or whether it really worked. So after some research, I got to the bottom of the mystery.

Cucumbers are members of the gourd family and all these vegetables release a compound called cucurbitacins which are naturally bitter. It’s a process that these plants evolved to protect themselves from being eaten and are concentrated at the ends which is where animals would usually start eating in the wild. 

By sprinkling salt on the ends, it triggers a process of osmosis and the cucurbitacins are drawn out from the cells in a milky white fluid. By cutting off the ends and rubbing them together, you can enhance this reaction and prevent the cucurbitacins from spreading to the rest of the cucumber. The best way to do this is to do it before you peel the cucumber (if you are peeling it at all) and then give it a quick rinse to remove the white fluid. 

This doesn’t work on all cucumbers though since another enzyme called elaterase hydrolyses the bitter compounds. (which means that water and the compound, in this case, cucurbitacins, combine and decompose each other). Depending on where the cucumbers were grown and the amount of water available, the bitterness levels vary. The more water, the less bitter they are. This is why cucumbers that were bred indoors or in controlled environments tend to be less bitter than wild or organic ones that had to deal with variable weather conditions.

So there was my eureka moment, the day it all finally made sense. The many cucumber rubbings I had embarked on in my life were not in vain, there was a solid science behind this practice. It made me realise that no matter how much you learn about food, there’s always something new to discover and that sometimes, old wives' tales should be trusted.