How to smell
Experts never smell the base of the durian. Mr Goh Kwee Leng, 58, owner of 717 Trading, says: "The base of the husk is the thickest part so it is harder to smell the aroma of the fruit."
Instead, sniff along the seams or split lines of the durian - you should smell a slight fragrance. If there is no aroma, the durian is unripe. If the aroma is too strong, the durian is probably over-ripe.
The right shape
The best durians are oval or slightly oblong in shape. Odd-shaped fruit are likely to have fewer chambers inside and so fewer flesh-covered seeds.
A perfectly round durian may have sub-standard fruit because it is usually less aromatic and the seeds are usually bigger and the meat less fleshy and creamy.
Different varieties of durians come in different sizes. For example, XO durians are generally smaller while there are no small Red Prawn durians - these are generally large fruit. So be suspicious if a seller points to a large XO durian or a small Red Prawn one.
Trick of the trade
Some sellers try to push durians that have been rejected by other customers. Watch the vendors to ensure that they are opening a new durian.
Instead of prodding the flesh-covered seeds when the seller presents an open fruit, customers should taste the durian. If it is bad, or not the variety promised, they are not obliged to buy it, sellers say.
Mr Richard Woo, 40, general manager of Four Seasons Durian Cafe, says: "When you pinch or prod the fruit, you are touching only the skin and not the flesh, so there is no way to tell if the fruit is good. Taste it instead, that way you can really tell if the durian is any good."
The real deal
To make sure a seller isn't passing off a lesser durian as a Mao Shan Wang, look for prominent seams radiating from the base of the durian. The seams are lines where the spikes of the durian run parallel to each other. The base of a real D24 durian has a flat round spot about half the size of a 5-cent coin.
This article was originally published in The Straits Times on 21 June 2015.