Why do oranges taste the way they do? Researchers have finally broken it down

Scientists might soon be able to create disease-resistant orange hybrids that taste as good as the originals.

According to a study published in the journalScience Advances, chemical analysis has revealed 26 compounds responsible for the distinctive flavour of oranges.

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In the last few decades, huanglongbing, a citrus greening disease, has heavily impacted the global production of citrus fruits. The HLB bacteria which causes this disease infects most citrus cultivars, species, hybrids and even some citrus relatives. Due to this, the fruit bears no value as they have a poor size and quality. Moreover, there's no cure for the disease, and rapid tree removal is the only prevention.

Anne Plotto of the United States Horticultural Research Laboratory in Florida told the New Scientist that this disease has particularly affected the production of oranges.

"Sweet orange (Citrus sinensis) exhibits limited genetic diversity and high susceptibility to Huanglongbing (HLB)," the study said. Plotto and her team wanted to find out whether it was possible to generate orange hybrids resistant to the citrus greening disease while maintaining the signature flavour of oranges.

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The research team analysed 179 juice specimens from a range of citruses. These included oranges, mandarins (Citrus reticulata), trifoliate oranges (Citrus trifoliata) and other hybrids. Moreover, trained citrus testers also tried each juice sample and ranked these on how they tasted like orange juice.

The study revealed that juices with the most prominent orange flavour contained all 26 specific compounds. Seven of these compounds are known as esters. They appeared to be the prime components in differentiating the taste of oranges and mandarins.

When Plotto and her colleagues conducted a genetic analysis of the citrus fruits, they found a gene responsible for producing these seven esters. They dubbed it C. sinensis alcohol acyltransferase 1.

The study mentioned, "Its activity was validated through overexpression assays. Phylogeny revealed the functional allele was inherited from pummelo. A SNP-based DNA marker in the coding region accurately predicted phenotypes."

"This gene is expressed much more in the cultivars that produce a lot of esters," said team member Zhen Fan.

According to Plotto, the study could eventually help create disease-tolerant hybrids with a rich orange flavour. "The findings could be used to screen citrus hybrid seedlings for desired orange flavour at an early stage, instead of waiting 10 to 15 years for the tree to bear fruits," she added.

(With inputs from agencies)