Sugar is not as responsible for the sour taste of citrus fruits

17 Mar 2020

Sugar is not as responsible for the sour taste of citrus fruits

Sugar is not as responsible for the sour taste of citrus fruitsResearchers Ronald Koes from the University of Amsterdam in collaboration with Mikael Roose from the University of California, Riverside studied the mystery of why citrus fruits taste sour.

Can the results help create a sweeter variety of citrus fruit?

Citrus fruits – lime (nimbu), sweet lime (mausambi), lemon, oranges, tangerines etc. have widely varying degrees of sourness and sweetness.
 	Surprisingly, researchers found that both sour and sweet citrus fruits have about the same amounts of natural sugar in them.
 	The reason they taste different was simply because of the presence of a single element – hydrogen, in an ionised* form called a proton. Citrus fruits with more protons taste sourer.

Researchers studied further for why some citrus varieties had more protons than others:

They found that plants lock protons in a part of their cells* called vacuoles (which work like a storage compartment in the cell).
 	Two genes*, called CitPH1 and CitPH5 are responsible for pumping the protons into these vacuoles.
 	Over thousands of years, different citrus varieties have emerged that have these two genes switched either on or off. Simply put, as long as these two genes are active, protons are higher and the fruit is sourer.

In 2014, Ronald Koes had already found the role of CitPH1 and CitPH5 in a plant variety called Petunia. Petunias look red or blue depending on more or fewer protons. The recent study shows how the two genes work in citrus fruits.

*ionised – If an atom has an increase or decrease in electrons it is called an ion or said to be ionised.

*cells – these are the smallest building blocks of anything that lives. Cells are in turn made of atoms, but atoms do not have life.

Author: Shirley

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Researchers Ronald Koes from the University of Amsterdam in collaboration with Mikael Roose from the University of California, Riverside studied the mystery of why citrus […]

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