Order a white coffee and what arrives depends on where you are standing. In Britain it simply means black coffee with a cold or room temperature whitener, which is what separates it from a café au lait made with steamed milk. In New England and New York the same drink is light or regular coffee. In American specialty cafes, white coffee means beans pulled from the roaster at a yellow roast, brewed as espresso into a thin, nutty, acidic, low bitterness shot, often discarding the first pour. The beans stay dense because they never expand like popcorn, which is why sellers suggest buying them pre ground.

The episode tests the claim that yellow roast is extra caffeinated: caffeine sublimes around 352 degrees Fahrenheit, yet it survives dark roasts largely intact, so the content by weight is essentially the same. In Ipoh, Malaysia, white coffee means imported beans roasted in margarine and served with condensed milk, often sold as 3 in 1 packets. Johor uses Liberica without margarine, Indonesia’s kopi putih uses a short, low heat roast, and Singapore’s kopitiam filters coffee through a cloth sock. Yemen brews white coffee from the cherry husk, and in the Levant kahwa bida contains no coffee at all.

• Malaysian white coffee does not come from a special plant, despite what many tourists believe.
• Roasting in margarine caramelizes fats and sugars on the bean’s surface.
• Kopitiam joins the Malay word for coffee with the Hokkien word for shop.
• The cloth sock lets heavy coffee oils through, giving a syrupy body that stands up to condensed milk.
• Kahwa bida is hot water with orange blossom or rose water, served after meals in Syria and Lebanon.