Lime, Orange, or Neither?

A citrus debate at the Pinhão Train Station

While waiting for the next train in Pinhão in June, I eavesdropped on an intriguing citrus debate.

A tourist I'll call Matt was standing under a fruit tree  near the platform, explaining to another traveler why the small green citrus hanging off it was probably an orange. His theory: "Well in Thailand, since the Western countries brought over the oranges, it mixed in with something over there, and then the skin stays green." When someone asked how you'd actually tell an orange from a lime over in Thailand, Matt shrugged and said, "I wouldn't be surprised if the word for orange and lime are the same."

I've run into lime and lemon words sounding similar in Southeast Asian languages before, but oranges joining that mix was a new one. So while Matt searched for a way to break into his fruit, I decided to fact-check him properly.

Fact check #1: Do ripe oranges stay green in Thailand?

True. But the mechanism isn't quite what Matt implied. Citrus peel color comes down to two pigments: green chlorophyll and orange/yellow carotenoids. The carotenoids are there the whole time, just masked by chlorophyll. What breaks the chlorophyll down is a cold snap, cool nighttime temperatures signal the fruit to shed its green layer and reveal the orange underneath. In consistently warm, tropical climates (like in Southeast Asia) that temperature drop never comes, so fully ripe oranges can stay green indefinitely. 

Fact check #2: Did oranges come from Western countries?

False. Oranges originated in Asia. When the trees were later grown in colder climates like Europe, that seasonal chill is what gave us the orange-colored orange we now think of as default. 

Fact check #3: Is the Thai word for orange the same as the word for lime?

False.

• Orange = ส้ม (*sôm*)

• Lime = มะนาว (*má-naao*)

Not the same word. 

The verdict: lime or orange?

Matt eventually picked a rock off the ground, cut into the fruit, gave it a sniff, and declared, "It's definitely an orange." I didn't get a look at the flesh myself as I was more interested in what was across the street, which was an unmistakable orange tree, ripe and orange-colored, no debate necessary.

Here is my photo of the tree in question:

I thought to myself, “if it wasn’t even a lime or an orange. What if it was a lemon?”

What do you think, lime, orange or neither? Let me know in the comments.